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Abstract
SrTiO3 is an insulating material which, using chemical doping, pressure, strain or isotope substitution, can be turned into a ferroelectric material or into a superconductor. The material itself, and the two aforementioned phenomena, have been subjects of intensive research of Karl Alex Müller and have been a source of inspiration, among other things, for his Nobel prize-winning research on high temperature superconductivity. An intriguing outstanding question is whether the occurrence of ferroelectricity and superconductivity in the same material is just a coincidence, or whether a deeper connection exists. In addition there is the empirical question of how these two phenomena interact with each other. Here we show that it is possible to induce superconductivity in a two-dimensional layer at the interface of SrTiO3 and LaAlO3 when we make the SrTiO3 ferroelectric by means of 18O substitution. Our experiments indicate that the ferroelectricity is perfectly compatible with having a superconducting two-dimensional electron system at the interface. This provides a promising avenue for manipulating superconductivity in a non centrosymmetric environment.
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52
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Shi XL, Zou J, Chen ZG. Advanced Thermoelectric Design: From Materials and Structures to Devices. Chem Rev 2020; 120:7399-7515. [PMID: 32614171 DOI: 10.1021/acs.chemrev.0c00026] [Citation(s) in RCA: 377] [Impact Index Per Article: 94.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The long-standing popularity of thermoelectric materials has contributed to the creation of various thermoelectric devices and stimulated the development of strategies to improve their thermoelectric performance. In this review, we aim to comprehensively summarize the state-of-the-art strategies for the realization of high-performance thermoelectric materials and devices by establishing the links between synthesis, structural characteristics, properties, underlying chemistry and physics, including structural design (point defects, dislocations, interfaces, inclusions, and pores), multidimensional design (quantum dots/wires, nanoparticles, nanowires, nano- or microbelts, few-layered nanosheets, nano- or microplates, thin films, single crystals, and polycrystalline bulks), and advanced device design (thermoelectric modules, miniature generators and coolers, and flexible thermoelectric generators). The outline of each strategy starts with a concise presentation of their fundamentals and carefully selected examples. In the end, we point out the controversies, challenges, and outlooks toward the future development of thermoelectric materials and devices. Overall, this review will serve to help materials scientists, chemists, and physicists, particularly students and young researchers, in selecting suitable strategies for the improvement of thermoelectrics and potentially other relevant energy conversion technologies.
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Affiliation(s)
- Xiao-Lei Shi
- Centre for Future Materials, University of Southern Queensland, Springfield Central, Queensland 4300, Australia.,School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Jin Zou
- School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia.,Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Zhi-Gang Chen
- Centre for Future Materials, University of Southern Queensland, Springfield Central, Queensland 4300, Australia.,School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia
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53
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Chen Y, Lechaux Y, Casals B, Guillet B, Minj A, Gázquez J, Méchin L, Herranz G. Photoinduced Persistent Electron Accumulation and Depletion in LaAlO_{3}/SrTiO_{3} Quantum Wells. PHYSICAL REVIEW LETTERS 2020; 124:246804. [PMID: 32639817 DOI: 10.1103/physrevlett.124.246804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 05/14/2020] [Indexed: 06/11/2023]
Abstract
Persistent photoconductance is a phenomenon found in many semiconductors, by which light induces long-lived excitations in electronic states. Commonly, persistent photoexcitation leads to an increase of carriers (accumulation), though occasionally it can be negative (depletion). Here, we present the quantum well at the LaAlO_{3}/SrTiO_{3} interface, where in addition to photoinduced accumulation, a secondary photoexcitation enables carrier depletion. The balance between both processes is wavelength dependent, and allows tunable accumulation or depletion in an asymmetric manner, depending on the relative arrival time of photons of different frequencies. We use Green's function formalism to describe this unconventional photoexcitation, which paves the way to an optical implementation of neurobiologically inspired spike-timing-dependent plasticity.
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Affiliation(s)
- Yu Chen
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
| | - Yoann Lechaux
- Normandie Univ, UNICAEN, ENSICAEN, CNRS, GREYC, 14000 Caen, France
| | - Blai Casals
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
| | - Bruno Guillet
- Normandie Univ, UNICAEN, ENSICAEN, CNRS, GREYC, 14000 Caen, France
| | - Albert Minj
- Normandie Univ, UNICAEN, ENSICAEN, CNRS, GREYC, 14000 Caen, France
- IMEC, Kapeldreef 75, Leuven 3000, Belgium
| | - Jaume Gázquez
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
| | - Laurence Méchin
- Normandie Univ, UNICAEN, ENSICAEN, CNRS, GREYC, 14000 Caen, France
| | - Gervasi Herranz
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
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54
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Ayino Y, Yue J, Wang T, Jalan B, Pribiag VS. Effects of paramagnetic pair-breaking and spin-orbital coupling on multi-band superconductivity. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:38LT02. [PMID: 32422615 DOI: 10.1088/1361-648x/ab940c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 05/18/2020] [Indexed: 06/11/2023]
Abstract
The BCS picture of superconductivity describes pairing between electrons originating from a single band. A generalization of this picture occurs in multi-band superconductors, where electrons from two or more bands contribute to superconductivity. The contributions of the different bands can result in an overall enhancement of the critical field and can lead to qualitative changes in the temperature dependence of the upper critical field when compared to the single-band case. While the role of orbital pair-breaking on the critical field of multi-band superconductors has been explored extensively, paramagnetic and spin-orbital scattering effects have received comparatively little attention. Here we investigate this problem using thin films of Nd-doped SrTiO3. We furthermore propose a model for analyzing the temperature-dependence of the critical field in the presence of orbital, paramagnetic and spin-orbital effects, and find a very good agreement with our data. Interestingly, we also observe a dramatic enhancement in the out-of-plane critical field to values well in excess of the Chandrasekhar-Clogston (Pauli) paramagnetic limit, which can be understood as a consequence of multi-band effects in the presence of spin-orbital scattering.
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Affiliation(s)
- Yilikal Ayino
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Jin Yue
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Tianqi Wang
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Bharat Jalan
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Vlad S Pribiag
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, United States
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55
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Liu M, Hong Y, Xue H, Meng J, Jiang W, Zhang Z, Ling J, Dou R, Xiong C, He L, Nie J. Enhancement of Rashba spin-orbit coupling by electron confinement at the LaAlO 3/SrTiO 3 interface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:235003. [PMID: 32050164 DOI: 10.1088/1361-648x/ab7579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Electrical transport property is closely related to the dimensionality of carriers' distribution. In this work, we succeed in tuning the carriers' distribution and the Rashba spin-orbit coupling at LaAlO3/SrTiO3 interface by varying the oxygen pressure (c-P O2) adopted in crystalline LaAlO3 growth. Measurements of the in-plane anisotropic magnetoresistance and the conducting-layer thickness indicate that the carriers' distribution changes from three to two dimensions with c-P O2 increasing, i.e. the electron confinement gets stronger. Importantly, by measuring the low-temperature out-of-plane magnetoresistance and analyzing the weak localization/weak anti-localization, we find that the strength of Rashba spin-orbit coupling can be enhanced by electron confinement. The electron confinement is a manifestation of breaking of spatial inversion symmetry. Therefore, our work reveals the intimate relationship between spatial inversion symmetry breaking and Rashba spin-orbit coupling at the LaAlO3/SrTiO3 interface, and provides a new method to tune the Rashba spin-orbit coupling, which is valuable in the application of oxide-spintronics.
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Affiliation(s)
- Mingrui Liu
- Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
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56
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Wang Y, Qian P, Liu Y, Zhang FM, Cai HL, Wu XS, Zhang GP. Modulating the electronic and optical properties for SrTiO 3/LaAlO 3 bilayers treated as the 2D materials by biaxial strains. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:215701. [PMID: 31995526 DOI: 10.1088/1361-648x/ab70c3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The emerging two-dimensional (2D) materials such as graphene have opened the door to industrial applications. Here, we consider the oxide perovskite monolayer of SrTiO3 (STO), LaAlO3 (LAO) and their heterostructures as the 2D transitional metal system. Results show that a band-gap transition from indirect to direct occurs when the separated monolayer STO (indirect band gap of 3.210 eV), and LAO (indirect band gap of 4.024 eV), form the heterostructures (direct band gap of 2.976 eV). The obtained bandgap for the stable bilayers may effectively be modulated by biaxial strains from -12% to 8%. With 12% compressive biaxial strain, the band gap reduces to be 0.23 eV. The optical properties for the stable bilayers are also tuned by the biaxial strain. When the strain increases from compressive strain to tensile strain, the strongest peak of the imaginary part of dielectric function red shifts to lower energy. In comparing with the monolayer STO and LAO, the elastic property enhances obviously for the stable heterostructure, suggesting the heterostructure can be more stable freestanding or may be applied in device fabrications.
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Affiliation(s)
- Yan Wang
- Collaborative Innovation Center of Advanced Microstructures, Laboratory of Solid State Microstructures & School of Physics, Nanjing University, Nanjing 210093, People's Republic of China
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57
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Yan H, Zhang Z, Li M, Wang S, Ren L, Jin K. Photoresponsive properties at (0 0 1), (1 1 1) and (1 1 0) LaAlO 3/SrTiO 3 interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:135002. [PMID: 31801125 DOI: 10.1088/1361-648x/ab5ebf] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report the photoresponsive characteristics of (0 0 1), (1 1 0), and (1 1 1) LaAlO3/SrTiO3 heterointerfaces deposited at different oxygen pressures using a 360 nm light. The results show that LaAlO3/SrTiO3 interfaces with less oxygen vacancies exhibit a larger resistance change when illuminated by light and a slower recovery process when light is off. In addition, the (1 1 0) LaAlO3/SrTiO3 heterointerfaces present the smallest photoinduced change and residual photoinduced change in the resistance, which are related to the negligible polarization discontinuity at the interfaces. Our results provide a deeper insight into the photoinduced properties in the 2D electron gas system, paving the way for the design of oxide optoelectronic devices.
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Affiliation(s)
- Hong Yan
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions, School of Science, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
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58
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Nathabumroong S, Eknapakul T, Jaiban P, Yotburut B, Siriroj S, Saisopa T, Mo SK, Supruangnet R, Nakajima H, Yimnirun R, Maensiri S, Meevasana W. Interplay of negative electronic compressibility and capacitance enhancement in lightly-doped metal oxide Bi 0.95La 0.05FeO 3 by quantum capacitance model. Sci Rep 2020; 10:5153. [PMID: 32198381 PMCID: PMC7083945 DOI: 10.1038/s41598-020-61859-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 02/24/2020] [Indexed: 12/03/2022] Open
Abstract
Light-sensitive capacitance variation of Bi0.95La0.05FeO3 (BLFO) ceramics has been studied under violet to UV irradiation. The reversible capacitance enhancement up to 21% under 405 nm violet laser irradiation has been observed, suggesting a possible degree of freedom to dynamically control this in high dielectric materials for light-sensitive capacitance applications. By using ultraviolet photoemission spectroscopy (UPS), we show here that exposure of BLFO surfaces to UV light induces a counterintuitive shift of the O2p valence state to lower binding energy of up to 243 meV which is a direct signature of negative electronic compressibility (NEC). A decrease of BLFO electrical resistance agrees strongly with the UPS data suggesting the creation of a thin conductive layer on its insulating bulk under light irradiation. By exploiting the quantum capacitance model, we find that the negative quantum capacitance due to this NEC effect plays an important role in this capacitance enhancement
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Affiliation(s)
- S Nathabumroong
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand
| | - T Eknapakul
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand
| | - P Jaiban
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand.,Faculty of science, Energy and Environment, King Mongkut's University of Technology North Bangkok, Rayong Campus, Rayong, 21120, Thailand
| | - B Yotburut
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand.,Thailand Center of Excellence in Physics (ThEP), MHSRI, Bangkok, 10400, Thailand
| | - S Siriroj
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand
| | - T Saisopa
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand
| | - S-K Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - R Supruangnet
- Synchrotron Light Research Institute, Nakhon Ratchasima, 30000, Thailand
| | - H Nakajima
- Synchrotron Light Research Institute, Nakhon Ratchasima, 30000, Thailand
| | - R Yimnirun
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand.,School of Energy Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Rayong, 21210, Thailand
| | - S Maensiri
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand
| | - W Meevasana
- School of Physics and Center of Excellence on Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand. .,Thailand Center of Excellence in Physics (ThEP), MHSRI, Bangkok, 10400, Thailand.
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59
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Two-dimensional Electron Gas at Thiol/ZnO Interface. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2020. [DOI: 10.1380/ejssnt.2020.41] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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60
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Yin C, Smink AEM, Leermakers I, Tang LMK, Lebedev N, Zeitler U, van der Wiel WG, Hilgenkamp H, Aarts J. Electron Trapping Mechanism in LaAlO_{3}/SrTiO_{3} Heterostructures. PHYSICAL REVIEW LETTERS 2020; 124:017702. [PMID: 31976734 DOI: 10.1103/physrevlett.124.017702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Revised: 09/13/2019] [Indexed: 06/10/2023]
Abstract
In LaAlO_{3}/SrTiO_{3} heterostructures, a still poorly understood phenomenon is that of electron trapping in back-gating experiments. Here, by combining magnetotransport measurements and self-consistent Schrödinger-Poisson calculations, we obtain an empirical relation between the amount of trapped electrons and the gate voltage. The amount of trapped electrons decays exponentially away from the interface. However, contrary to earlier observations, we find that the Fermi level remains well within the quantum well. The enhanced trapping of electrons induced by the gate voltage can therefore not be explained by a thermal escape mechanism. Further gate sweeping experiments strengthen that conclusion. We propose a new mechanism which involves the electromigration and clustering of oxygen vacancies in SrTiO_{3} and argue that such electron trapping is a universal phenomenon in SrTiO_{3}-based two-dimensional electron systems.
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Affiliation(s)
- Chunhai Yin
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Alexander E M Smink
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Inge Leermakers
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Lucas M K Tang
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Nikita Lebedev
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Uli Zeitler
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Wilfred G van der Wiel
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Hans Hilgenkamp
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Jan Aarts
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
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61
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Trier F, Vaz DC, Bruneel P, Noël P, Fert A, Vila L, Attané JP, Barthélémy A, Gabay M, Jaffrès H, Bibes M. Electric-Field Control of Spin Current Generation and Detection in Ferromagnet-Free SrTiO 3-Based Nanodevices. NANO LETTERS 2020; 20:395-401. [PMID: 31859513 DOI: 10.1021/acs.nanolett.9b04079] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Spintronics entails the generation, transport, manipulation and detection of spin currents, usually in hybrid architectures comprising interfaces whose impact on performance is detrimental. In addition, how spins are generated and detected is generally material specific and determined by the electronic structure. Here, we demonstrate spin current generation, transport and electrical detection, all within a single non-magnetic material system: a SrTiO3 two-dimensional electron gas (2DEG) with Rashba spin-orbit coupling. We show that the spin current is generated from a charge current by the 2D spin Hall effect, transported through a channel and reconverted into a charge current by the inverse 2D spin Hall effect. Furthermore, by adjusting the Fermi energy with a gate voltage we tune the generated and detected spin polarization and relate it to the complex multiorbital band structure of the 2DEG. We discuss the leading mechanisms of the spin-charge interconversion processes and argue for the potential of quantum oxide materials for future all-electrical low-power spin-based logic.
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Affiliation(s)
- Felix Trier
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
| | - Diogo C Vaz
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
| | - Pierre Bruneel
- Laboratoire de Physique des Solides UMR 8502 , Université Paris-Sud, Université Paris-Saclay , 91405 Orsay , France
| | - Paul Noël
- Université Grenoble Alpes, CEA, CNRS, Spintec , 38000 Grenoble , France
| | - Albert Fert
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
| | - Laurent Vila
- Université Grenoble Alpes, CEA, CNRS, Spintec , 38000 Grenoble , France
| | | | - Agnès Barthélémy
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
| | - Marc Gabay
- Laboratoire de Physique des Solides UMR 8502 , Université Paris-Sud, Université Paris-Saclay , 91405 Orsay , France
| | - Henri Jaffrès
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
| | - Manuel Bibes
- Unité Mixte de Physique , CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay , 91767 Palaiseau , France
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62
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63
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Okamura K. Focus on the overlap density of wavefunctions in GW approximations. Phys Chem Chem Phys 2020; 22:5366-5376. [DOI: 10.1039/c9cp06862g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A quasiparticle energy in GW approximations depends primarily on spatially overlapped and symmetrically compatible wavefunctions.
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64
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Mori R, Marshall PB, Ahadi K, Denlinger JD, Stemmer S, Lanzara A. Controlling a Van Hove singularity and Fermi surface topology at a complex oxide heterostructure interface. Nat Commun 2019; 10:5534. [PMID: 31797932 PMCID: PMC6892806 DOI: 10.1038/s41467-019-13046-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 10/16/2019] [Indexed: 11/10/2022] Open
Abstract
The emergence of saddle-point Van Hove singularities (VHSs) in the density of states, accompanied by a change in Fermi surface topology, Lifshitz transition, constitutes an ideal ground for the emergence of different electronic phenomena, such as superconductivity, pseudo-gap, magnetism, and density waves. However, in most materials the Fermi level, \documentclass[12pt]{minimal}
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\begin{document}$${E}_{{\rm{F}}}$$\end{document}EF, is too far from the VHS where the change of electronic topology takes place, making it difficult to reach with standard chemical doping or gating techniques. Here, we demonstrate that this scenario can be realized at the interface between a Mott insulator and a band insulator as a result of quantum confinement and correlation enhancement, and easily tuned by fine control of layer thickness and orbital occupancy. These results provide a tunable pathway for Fermi surface topology and VHS engineering of electronic phases. A singularity in a material’s density of states at the Fermi energy can drive the formation of unconventional electronic phases. Here the authors show a Van Hove singularity is tunable across the Fermi energy in an oxide heterostructure, leading to enhanced electronic correlations.
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Affiliation(s)
- Ryo Mori
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.,Applied Science & Technology, University of California, Berkeley, CA, 94720, USA
| | - Patrick B Marshall
- Materials Department, University of California, Santa Barbara, CA, 93106-5050, USA
| | - Kaveh Ahadi
- Materials Department, University of California, Santa Barbara, CA, 93106-5050, USA
| | - Jonathan D Denlinger
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Susanne Stemmer
- Materials Department, University of California, Santa Barbara, CA, 93106-5050, USA
| | - Alessandra Lanzara
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. .,Department of Physics, University of California, Berkeley, CA, 94720, USA.
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65
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Lu X, Sun L, Jiang P, Bao X. Progress of Photodetectors Based on the Photothermoelectric Effect. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1902044. [PMID: 31483546 DOI: 10.1002/adma.201902044] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 07/06/2019] [Indexed: 06/10/2023]
Abstract
High-performance uncooled photodetectors operating in the long-wavelength infrared and terahertz regimes are highly demanded in the military and civilian fields. Photothermoelectric (PTE) detectors, which combine photothermal and thermoelectric conversion processes, can realize ultra-broadband photodetection without the requirement of a cooling unit and external bias. In the last few decades, the responsivity and speed of PTE-based photodetectors have made impressive progress with the discovery of novel thermoelectric materials and the development of nanophotonics. In particular, by introducing hot-carrier transport into low-dimensional material-based PTE detectors, the response time has been successfully pushed down to the picosecond level. Furthermore, with the assistance of surface plasmon, antenna, and phonon absorption, the responsivity of PTE detectors can be significantly enhanced. Beyond the photodetection, PTE effect can also be utilized to probe exotic physical phenomena in spintronics and valleytronics. Herein, recent advances in PTE detectors are summarized, and some potential strategies to further improve the performance are proposed.
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Affiliation(s)
- Xiaowei Lu
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China
| | - Lin Sun
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China
| | - Peng Jiang
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China
| | - Xinhe Bao
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China
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66
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On the emergence of conductivity at SrTiO 3-based oxide interfaces - an in-situ study. Sci Rep 2019; 9:18005. [PMID: 31784583 PMCID: PMC6884556 DOI: 10.1038/s41598-019-54463-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 11/09/2019] [Indexed: 11/08/2022] Open
Abstract
Heterostructures and crystal interfaces play a major role in state-of-the-art semiconductor devices and play a central role in the field of oxide electronics. In oxides the link between the microscopic properties of the interfaces and bulk properties of the resulting heterostructures challenge our fundamental understanding. Insights on the early growth stage of interfaces and its influence on resulting physical properties are scarce - typically the information is inferred from post growth characterization. Here, we report on real time measurements of the transport properties of SrTiO3-based heterostructures at room temperature, while the heterostructure is forming. Surprisingly, we detect a conducting interface already at the initial growth stage, much earlier than the well-established critical thickness limit for observing conductivity ex-situ after sample growth. We investigate how the conductivity depends on various physical processes occurring during pulsed laser depositions, including light illumination, particle bombardment by the plasma plume, interactions with the atmosphere and oxygen migration from SrTiO3 to the thin films of varying compositions. We conclude that the conductivity in these room-temperature grown interfaces stem from oxygen vacancies with a concentration determined primarily by a balance between vacancy formation through particle bombardment and interfacial redox reaction and vacancy annihilation through oxidation. Using this approach, we propose a new design tool to control the electrical properties of interfaces in real time during their formation.
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67
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Fukutani K, Stania R, Jung J, Schwier EF, Shimada K, Kwon CI, Kim JS, Yeom HW. Electrical Tuning of the Excitonic Insulator Ground State of Ta_{2}NiSe_{5}. PHYSICAL REVIEW LETTERS 2019; 123:206401. [PMID: 31809082 DOI: 10.1103/physrevlett.123.206401] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Indexed: 06/10/2023]
Abstract
We demonstrate that the excitonic insulator ground state of Ta_{2}NiSe_{5} can be electrically controlled by electropositive surface adsorbates. Our studies utilizing angle-resolved photoemission spectroscopy reveal intriguing wave-vector-dependent deformations of the characteristic flattop valence band of this material upon potassium adsorption. The observed band deformation indicates a reduction of the single-particle band gap due to the Stark effect near the surface. The present study provides the foundation for the electrical tuning of the many-body quantum states in excitonic insulators.
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Affiliation(s)
- Keisuke Fukutani
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
| | - Roland Stania
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
| | - Jiwon Jung
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Eike F Schwier
- Hiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima, Hiroshima, Japan
| | - Kenya Shimada
- Hiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima, Hiroshima, Japan
| | - Chang Il Kwon
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Jun Sung Kim
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Han Woong Yeom
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
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68
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Song C, Li X, Jiang Y, Wang X, Yao J, Meng S, Zhang J. Real-Space Imaging of Orbital Selectivity on SrTiO 3(001) Surface. ACS APPLIED MATERIALS & INTERFACES 2019; 11:37279-37284. [PMID: 31529959 DOI: 10.1021/acsami.9b11724] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Real-space access of the orbital degree of freedom in complex oxides is still challenging due to intricate electronic hybridization. Here, we report a direct observation of reproducible orbital-selective tunneling on a novel SrTiO3(001) surface by scanning tunneling microscopy. The electronic structures reversibly switch between two different sets of symmetries depending on the sample bias, which is accompanied by a remarkable change in energy-dependent spectroscopy data. Tunneling spectrum combined with density functional theory calculations elucidates that symmetry-breaking at the surface determines the crystal-splitting field of eg/t2g orbitals with a strong in-plane anisotropy so that electrons alternatingly fill eg and t2g orbitals during the imaging process with different biases. This surface superstructure provides a new strategy toward understanding orbital textures and orbital selectivity in complex oxides.
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Affiliation(s)
- Chuangye Song
- Department of Physics , Beijing Normal University , Beijing 100875 , China
| | - Xuanyi Li
- Institute of Physics , Chinese Academic of Science , Beijing 100190 , China
- School of Physics , University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Ying Jiang
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Xi Wang
- Key Laboratory of Luminescence and Optical Information, Ministry of Education, Department of Physics, School of Science , Beijing Jiaotong University , Beijing 100044 , China
- Chemistry and Chemical Engineering Guangdong Laboratory , Shantou 515031 , China
| | - Jiannian Yao
- Chemistry and Chemical Engineering Guangdong Laboratory , Shantou 515031 , China
- Key Laboratory of Photochemistry, Institute of Chemistry , Chinese Academy of Science , Beijing 100190 , China
| | - Sheng Meng
- Institute of Physics , Chinese Academic of Science , Beijing 100190 , China
- School of Physics , University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Jinxing Zhang
- Department of Physics , Beijing Normal University , Beijing 100875 , China
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69
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Dai W, Liang Y, Yang M, Schrecongost D, Gajurel P, Lee H, Lee JW, Chen J, Eom CB, Cen C. Large and Reconfigurable Infrared Photothermoelectric Effect at Oxide Interfaces. NANO LETTERS 2019; 19:7149-7154. [PMID: 31525937 DOI: 10.1021/acs.nanolett.9b02712] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
To maximize the photovoltaic efficiency, it is highly desirable to enable the electricity conversion from low energy photons and to extract the excessive energy from hot carriers. Here we report a large photovoltage generation at the LaAlO3/SrTiO3 interfaces from infrared photons with energies far below the oxide bandgaps. This effect is a result of the photoexcitation of hot carriers in metasurface electrical contacts and the subsequent thermoelectric charge separations by the interfacial two-dimensional electron gas (2DEG). Reaching a room-temperature responsivity of 4.4 V/W, such light-to-charge conversion can be spatially controlled and reconfigured through the patterning of 2DEG using conducting atomic force microscope. Compatible for broadband applications, our results demonstrate a new path toward efficient and programmable light sensing using oxide-based low-dimensional electron systems.
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Affiliation(s)
- Weitao Dai
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
| | - Yi Liang
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
- Guangxi Key Lab for Relativistic Astrophysics, Center on Nanoenergy Research, School of Physical Science and Technology , Guangxi University, Nanning , Guangxi 530004 , China
| | - Ming Yang
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
| | - Dustin Schrecongost
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
| | - Prakash Gajurel
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
| | - Hyungwoo Lee
- Department of Material Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Jung-Woo Lee
- Department of Material Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Jun Chen
- Department of Electrical and Computer Engineering and Peterson Institute of NanoScience and Engineering , University of Pittsburgh , Pittsburgh , Pennsylvania 15261 , United States
| | - Chang-Beom Eom
- Department of Material Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Cheng Cen
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
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70
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Bhansali S, Khunsin W, Chatterjee A, Santiso J, Abad B, Martin-Gonzalez M, Jakob G, Sotomayor Torres CM, Chávez-Angel E. Enhanced thermoelectric properties of lightly Nb doped SrTiO 3 thin films. NANOSCALE ADVANCES 2019; 1:3647-3653. [PMID: 36133557 PMCID: PMC9419777 DOI: 10.1039/c9na00361d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 07/30/2019] [Indexed: 06/16/2023]
Abstract
Novel thermoelectric materials developed for operation at room temperature must have similar or better performance along with being as ecofriendly as those commercially used, e.g., Bi2Te3, in terms of their toxicity and cost. In this work, we present an in-depth study of the thermoelectric properties of epitaxial Nb-doped strontium titanate (SrTi1-x Nb x O3) thin films as a function of (i) doping concentration, (ii) film thickness and (iii) substrate type. The excellent crystal quality was confirmed by high resolution transmission electron microscopy and X-ray diffraction analysis. The thermoelectric properties were measured by the three-omega method (thermal conductivity) and van der Pauw method (electrical resistivity), complemented by Seebeck coefficient measurements. A maximum power factor of 8.9 × 10-3 W m-1 K-2 and a thermoelectric figure of merit of 0.49 were measured at room temperature in 50 nm-thick films grown on lanthanum strontium aluminate. The mechanisms behind this high figure of merit are discussed in terms of a possible two-dimensional electron gas, increase of the effective mass of the electrons, electron filtering and change in strain due to different substrates. The overall enhancement of the thermoelectric properties suggests that SrTi1-x Nb x O3 is a very promising n-type candidate for room- to high-temperature applications.
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Affiliation(s)
- S Bhansali
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, The Barcelona Institute of Science and Technology Campus UAB, Bellaterra 08193 Barcelona Spain
| | - W Khunsin
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, The Barcelona Institute of Science and Technology Campus UAB, Bellaterra 08193 Barcelona Spain
| | - A Chatterjee
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, The Barcelona Institute of Science and Technology Campus UAB, Bellaterra 08193 Barcelona Spain
| | - J Santiso
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, The Barcelona Institute of Science and Technology Campus UAB, Bellaterra 08193 Barcelona Spain
| | - B Abad
- Instituto de Microelectronica de Madrid, IMM-CNM, CSIC Isaac Newton, 8 PTM 28760 Tres Cantos (Madrid) Spain
| | - M Martin-Gonzalez
- Instituto de Microelectronica de Madrid, IMM-CNM, CSIC Isaac Newton, 8 PTM 28760 Tres Cantos (Madrid) Spain
| | - G Jakob
- Institut für Physik, Johannes Gutenberg Universität Mainz Staudingerweg 7 55128 Mainz Germany
- Graduate School Materials Science in Mainz Staudingerweg 9 55128 Mainz Germany
| | - C M Sotomayor Torres
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, The Barcelona Institute of Science and Technology Campus UAB, Bellaterra 08193 Barcelona Spain
- ICREA Passeig Lluis Companys 23 08010 Barcelona Spain
| | - E Chávez-Angel
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, The Barcelona Institute of Science and Technology Campus UAB, Bellaterra 08193 Barcelona Spain
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71
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Dichotomy of the photo-induced 2-dimensional electron gas on SrTiO 3 surface terminations. Proc Natl Acad Sci U S A 2019; 116:16687-16691. [PMID: 31391304 DOI: 10.1073/pnas.1821937116] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Oxide materials are important candidates for the next generation of electronics due to a wide array of desired properties, which they can exhibit alone or when combined with other materials. While SrTiO3 (STO) is often considered a prototypical oxide, it, too, hosts a wide array of unusual properties, including a 2-dimensional electron gas (2DEG), which can form at the surface when exposed to ultraviolet (UV) light. Using layer-by-layer growth of high-quality STO films, we show that the 2DEG only forms with the SrO termination and not with the TiO2 termination, contrary to expectation. This dichotomy of the observed angle-resolved photoemission spectroscopy (ARPES) spectra is similarly seen in BaTiO3 (BTO), in which the 2DEG is only observed for BaO-terminated films. These results will allow for a deeper understanding and better control of the electronic structure of titanate films, substrates, and heterostructures.
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72
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Piyanzina II, Eyert V, Lysogorskiy YV, Tayurskii DA, Kopp T. Oxygen vacancies and hydrogen doping in LaAlO 3/SrTiO 3 heterostructures: electronic properties and impact on surface and interface reconstruction. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:295601. [PMID: 30970333 DOI: 10.1088/1361-648x/ab1831] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We investigate the effect of oxygen vacancies and hydrogen dopants at the surface and inside slabs of [Formula: see text], [Formula: see text], and [Formula: see text]/[Formula: see text] heterostructures on the electronic properties by means of electronic structure calculations as based on density functional theory. Depending on the concentration, the presence of these defects in a [Formula: see text] slab can suppress the surface conductivity. In contrast, in insulating [Formula: see text] slabs already very small concentrations of oxygen vacancies or hydrogen dopant atoms induce a finite occupation of the conduction band. Surface defects in insulating [Formula: see text]/[Formula: see text] heterostructure slabs with three [Formula: see text] overlayers lead to the emergence of interface conductivity. Calculated defect formation energies reveal strong preference of hydrogen dopant atoms for surface sites for all structures and concentrations considered. Strong decrease of the defect formation energy of hydrogen adatoms with increasing thickness of the [Formula: see text] overlayer and crossover from positive to negative values, taken together with the metallic conductivity induced by hydrogen adatoms, seamlessly explains the semiconductor-metal transition observed for these heterostructures as a function of the overlayer thickness. Moreover, we show that the potential drop and concomitant shift of (layer resolved) band edges is suppressed for the metallic configuration. Finally, magnetism with stable local moments, which form atomically thin magnetic layers at the interface, is generated by oxygen vacancies either at the surface or the interface, or by hydrogen atoms buried at the interface. In particular, oxygen vacancies in the [Formula: see text] interface layer cause drastic downshift of the 3d e g states of the Ti atoms neighboring the vacancies, giving rise to strongly localized magnetic moments, which add to the two-dimensional background magnetization.
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Affiliation(s)
- I I Piyanzina
- Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, 86135 Augsburg, Germany. Institute of Physics, Kazan Federal University, 420008 Kazan, Russia
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73
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Khanna U, Rout PK, Mograbi M, Tuvia G, Leermakers I, Zeitler U, Dagan Y, Goldstein M. Symmetry and Correlation Effects on Band Structure Explain the Anomalous Transport Properties of (111) LaAlO_{3}/SrTiO_{3}. PHYSICAL REVIEW LETTERS 2019; 123:036805. [PMID: 31386445 DOI: 10.1103/physrevlett.123.036805] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Indexed: 06/10/2023]
Abstract
The interface between the two insulating oxides SrTiO_{3} and LaAlO_{3} gives rise to a two-dimensional electron system with intriguing transport phenomena, including superconductivity, which are controllable by a gate. Previous measurements on the (001) interface have shown that the superconducting critical temperature, the Hall density, and the frequency of quantum oscillations, vary nonmonotonically and in a correlated fashion with the gate voltage. In this Letter we experimentally demonstrate that the (111) interface features a qualitatively distinct behavior, in which the frequency of Shubnikov-de Haas oscillations changes monotonically, while the variation of other properties is nonmonotonic albeit uncorrelated. We develop a theoretical model, incorporating the different symmetries of these interfaces as well as electronic-correlation-induced band competition. We show that the latter dominates at (001), leading to similar nonmonotonicity in all observables, while the former is more important at (111), giving rise to highly curved Fermi contours, and accounting for all its anomalous transport measurements.
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Affiliation(s)
- Udit Khanna
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv, 6997801, Israel
| | - P K Rout
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv, 6997801, Israel
| | - Michael Mograbi
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv, 6997801, Israel
| | - Gal Tuvia
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv, 6997801, Israel
| | - Inge Leermakers
- High Field Magnet Laboratory (HFML-EFML), Radboud University, 6525 ED Nijmegen, Netherlands
| | - Uli Zeitler
- High Field Magnet Laboratory (HFML-EFML), Radboud University, 6525 ED Nijmegen, Netherlands
| | - Yoram Dagan
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv, 6997801, Israel
| | - Moshe Goldstein
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv, 6997801, Israel
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74
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He P, Zhang SSL, Zhu D, Shi S, Heinonen OG, Vignale G, Yang H. Nonlinear Planar Hall Effect. PHYSICAL REVIEW LETTERS 2019; 123:016801. [PMID: 31386424 DOI: 10.1103/physrevlett.123.016801] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 05/07/2019] [Indexed: 06/10/2023]
Abstract
An intriguing property of a three-dimensional (3D) topological insulator (TI) is the existence of surface states with spin-momentum locking, which offers a new frontier of exploration in spintronics. Here, we report the observation of a new type of Hall effect in a 3D TI Bi_{2}Se_{3} film. The Hall resistance scales linearly with both the applied electric and magnetic fields and exhibits a π/2 angle offset with respect to its longitudinal counterpart, in contrast to the usual angle offset of π/4 between the linear planar Hall effect and the anisotropic magnetoresistance. This novel nonlinear planar Hall effect originates from the conversion of a nonlinear transverse spin current to a charge current due to the concerted actions of spin-momentum locking and time-reversal symmetry breaking, which also exists in a wide class of noncentrosymmetric materials with a large span of magnitude. It provides a new way to characterize and utilize the nonlinear spin-to-charge conversion in a variety of topological quantum materials.
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Affiliation(s)
- Pan He
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore
| | - Steven S-L Zhang
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
- Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211, USA
| | - Dapeng Zhu
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore
| | - Shuyuan Shi
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore
| | - Olle G Heinonen
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Giovanni Vignale
- Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211, USA
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, and NUSNNI, National University of Singapore, 117576 Singapore
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75
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Leis A, Rodenbücher C, Szot K, Cherepanov V, Tautz FS, Voigtländer B. In-situ four-tip STM investigation of the transition from 2D to 3D charge transport in SrTiO 3. Sci Rep 2019; 9:2476. [PMID: 30792428 PMCID: PMC6384903 DOI: 10.1038/s41598-019-38888-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 12/13/2018] [Indexed: 11/08/2022] Open
Abstract
The electrical properties of SrTiO3(100) single crystals were investigated in-situ at different stages of thermal reduction by means of a 4-tip STM. Using the tips of the STM as electrical probes, distance-dependent four-point measurements were performed at the surface of the crystal at room temperature after reduction by thermal treatment. For annealing temperatures T ≤ 700 °C, charge transport is confined to a surface region <3 μm below the surface. For reduction at T ≥ 900 °C a transition from a conducting 2D sheet with insulating bulk to a system with dominant 3D bulk conductivity is found. At an intermediate reduction temperature of T = 800 °C, a regime with mixed 2D/3D contributions is observed in the distance-dependent resistance measurements. Describing the depth-dependent conductivity with an analytical N-layer model, this regime of mixed 2D/3D conductivity is evaluated quantitatively under the assumption of an exponentially decaying conductivity profile, correlated with the previously observed depth-dependent dislocation density in the sample. A non-monotonous temperature dependence of the 3D conductivity in the respective conducting layer is found and possible underlying mechanisms are discussed, particularly with regard to non-intrinsic material properties depending on details of the sample preparation.
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Affiliation(s)
- Arthur Leis
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425, Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425, Jülich, Germany
| | - Christian Rodenbücher
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425, Jülich, Germany
- Peter Grünberg Institut (PGI-7), Forschungszentrum Jülich, 52425, Jülich, Germany
- Institut für Energie- und Klimaforschung (IEK-3), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - Krzysztof Szot
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425, Jülich, Germany
- Peter Grünberg Institut (PGI-7), Forschungszentrum Jülich, 52425, Jülich, Germany
- A. Chełkowski Institute of Physics, University of Silesia, 40-007, Katowice, Poland
| | - Vasily Cherepanov
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425, Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425, Jülich, Germany
| | - F Stefan Tautz
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425, Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425, Jülich, Germany
| | - Bert Voigtländer
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425, Jülich, Germany.
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425, Jülich, Germany.
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76
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Lu X, Jiang P, Bao X. Phonon-enhanced photothermoelectric effect in SrTiO 3 ultra-broadband photodetector. Nat Commun 2019; 10:138. [PMID: 30635562 PMCID: PMC6329832 DOI: 10.1038/s41467-018-07860-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 10/31/2018] [Indexed: 11/09/2022] Open
Abstract
The self-powered and ultra-broadband photodetectors based on photothermoelectric (PTE) effect are promising for diverse applications such as sensing, environmental monitoring, night vision and astronomy. The sensitivity of PTE photodetectors is determined by the Seebeck coefficient and the rising temperature under illumination. Previous PTE photodetectors mostly rely on traditional thermoelectric materials with Seebeck coefficients in the range of 100 μV K−1, and array structures with multiple units are usually employed to enhance the photodetection performance. Herein, we demonstrate a reduced SrTiO3 (r-STO) based PTE photodetector with sensitivity up to 1.2 V W−1 and broadband spectral response from 325 nm to 10.67 μm. The high performance of r-STO PTE photodetector is attributed to its intrinsic high Seebeck coefficient and phonon-enhanced photoresponse in the long wavelength infrared region. Our results open up a new avenue towards searching for novel PTE materials beyond traditional thermoelectric materials for low-cost and high-performance photodetector at room temperature. Broadband photodetectors for various applications are in high demand, however, often suffering from non-linearities at high power densities. Here, a reduced strontium titanate based photodetector exhibiting linear response up to 1235 W/cm2 is presented not achieved by other broadband photodetectors.
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Affiliation(s)
- Xiaowei Lu
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, Dalian, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Peng Jiang
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, Dalian, China.
| | - Xinhe Bao
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, Dalian, China.
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77
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Baeumer C, Funck C, Locatelli A, Menteş TO, Genuzio F, Heisig T, Hensling F, Raab N, Schneider CM, Menzel S, Waser R, Dittmann R. In-Gap States and Band-Like Transport in Memristive Devices. NANO LETTERS 2019; 19:54-60. [PMID: 30241437 DOI: 10.1021/acs.nanolett.8b03023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Point defects such as oxygen vacancies cause emergent phenomena such as resistive switching in transition-metal oxides, but their influence on the electron-transport properties is far from being understood. Here, we employ direct mapping of the electronic structure of a memristive device by spectromicroscopy. We find that oxygen vacancies result in in-gap states that we use as input for single-band transport simulations. Because the in-gap states are situated below the Fermi level, they do not contribute to the current directly but impact the shape of the conduction band. Accordingly, we can describe our devices with band-like transport and tunneling across the Schottky barrier at the interface.
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Affiliation(s)
- Christoph Baeumer
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Carsten Funck
- Institute for Electronic Materials, IWE2 , RWTH Aachen University , 52074 Aachen , Germany
| | - Andrea Locatelli
- Elettra - Sincrotrone Trieste S.C.p.A., S.S. 14 km - 163,5 in AREA Science Park , I-34149 Basovizza , Trieste , Italy
| | - Tevfik Onur Menteş
- Elettra - Sincrotrone Trieste S.C.p.A., S.S. 14 km - 163,5 in AREA Science Park , I-34149 Basovizza , Trieste , Italy
| | - Francesca Genuzio
- Elettra - Sincrotrone Trieste S.C.p.A., S.S. 14 km - 163,5 in AREA Science Park , I-34149 Basovizza , Trieste , Italy
| | - Thomas Heisig
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Felix Hensling
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Nicolas Raab
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Claus M Schneider
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Stephan Menzel
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
| | - Rainer Waser
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
- Institute for Electronic Materials, IWE2 , RWTH Aachen University , 52074 Aachen , Germany
| | - Regina Dittmann
- Peter Gruenberg Institute , Forschungszentrum Juelich GmbH and JARA-FIT , 52425 Juelich , Germany
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78
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Yang M, Yan C, Ma Y, Li L, Cen C. Light induced non-volatile switching of superconductivity in single layer FeSe on SrTiO 3 substrate. Nat Commun 2019; 10:85. [PMID: 30622274 PMCID: PMC6325130 DOI: 10.1038/s41467-018-08024-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 12/10/2018] [Indexed: 11/09/2022] Open
Abstract
The capability of controlling superconductivity by light is highly desirable for active quantum device applications. Since superconductors rarely exhibit strong photoresponses, and optically sensitive materials are often not superconducting, efficient coupling between these two characters can be very challenging in a single material. Here we show that, in FeSe/SrTiO3 heterostructures, the superconducting transition temperature in FeSe monolayer can be effectively raised by the interband photoexcitations in the SrTiO3 substrate. Attributed to a light induced metastable polar distortion uniquely enabled by the FeSe/SrTiO3 interface, this effect only requires a less than 50 µW cm-2 continuous-wave light field. The fast optical generation of superconducting zero resistance state is non-volatile but can be rapidly reversed by applying voltage pulses to the back of SrTiO3 substrate. The capability of switching FeSe repeatedly and reliably between normal and superconducting states demonstrate the great potential of making energy-efficient quantum optoelectronics at designed correlated interfaces.
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Affiliation(s)
- Ming Yang
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia, 26506, USA.,National Key Laboratory of Science and Technology on Power Sources, Tianjin Institute of Power Sources, Tianjin, 300384, P. R. China
| | - Chenhui Yan
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia, 26506, USA
| | - Yanjun Ma
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia, 26506, USA
| | - Lian Li
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia, 26506, USA.
| | - Cheng Cen
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia, 26506, USA.
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79
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Gariglio S, Caviglia AD, Triscone JM, Gabay M. A spin-orbit playground: surfaces and interfaces of transition metal oxides. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2019; 82:012501. [PMID: 30058557 DOI: 10.1088/1361-6633/aad6ab] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Within the last twenty years, the status of the spin-orbit interaction has evolved from that of a simple atomic contribution to a key effect that modifies the electronic band structure of materials. It is regarded as one of the basic ingredients for spintronics, locking together charge and spin degrees of freedom and recently it is instrumental in promoting a new class of compounds, the topological insulators. In this review, we present the current status of the research on the spin-orbit coupling in transition metal oxides, discussing the case of two semiconducting compounds, [Formula: see text] and [Formula: see text], and the properties of surface and interfaces based on these. We conclude with the investigation of topological effects predicted to occur in different complex oxides.
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Affiliation(s)
- S Gariglio
- DQMP, University of Geneva, 24 Quai E.-Ansermet 1211, Geneva, Switzerland
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80
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Morimoto Y, Nishiyama J, Takeda H, Tsurumi T, Hoshina T. Transparent semiconducting SrTiO3 crystal fabricated by heating treatment with gaseous ammonia and CeO2 powder. Sci Rep 2018; 8:5031. [PMID: 29568047 PMCID: PMC5864887 DOI: 10.1038/s41598-018-23019-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 03/02/2018] [Indexed: 11/09/2022] Open
Abstract
A transparent semiconducting SrTiO3 single crystal with a resistivity of the order of 103 Ω·cm was fabricated by heating a SrTiO3 single crystal with gaseous ammonia and CeO2 powder. Conductive atomic force microscope (C-AFM) measurement revealed that micro-sized voids were formed and the high conductivity was exhibited only at around the voids. It is considered that the micro-sized voids were caused by the concentrated SrO planar defects, and TiO2-terminated structure with oxygen vacancies contributed to the two-dimensional conduction. In the heating process, the CeO2 powder acted as an oxygen source, and radicals such as NH2 and NH were generated by the reaction of oxygen and ammonia. The radicals may have contributed to the formation of three-dimensional network of the conductive paths consisting of SrO planar defects without the reduction of the bulk components. The electrons were localized on the TiO2-terminated structure, and the volume content of the conductive paths was small compared to the insulating bulk component. Therefore, the crystal was optically transparent and semiconducting.
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81
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Majorana Fermions in One-Dimensional Structures at LaAlO3/SrTiO3 Oxide Interfaces. CONDENSED MATTER 2018. [DOI: 10.3390/condmat3040037] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We study one-dimensional structures that may be formed at the LaAlO 3 /SrTiO 3 oxide interface by suitable top gating. These structures are modeled via a single-band model with Rashba spin-orbit coupling, superconductivity and a magnetic field along the one-dimensional chain. We first discuss the conditions for the occurrence of a topological superconducting phase and the related formation of Majorana fermions at the chain endpoints, highlighting a close similarity between this model and the Kitaev model, which also reflects in a similar condition the formation of a topological phase. Solving the model in real space, we also study the spatial extension of the wave function of the Majorana fermions and how this increases with approaching the limit condition for the topological state. Using a scattering matrix formalism, we investigate the stability of the Majorana fermions in the presence of disorder and discuss the evolution of the topological phase with increasing disorder.
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82
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Kawasaki JK, Kim CH, Nelson JN, Crisp S, Zollner CJ, Biegenwald E, Heron JT, Fennie CJ, Schlom DG, Shen KM. Engineering Carrier Effective Masses in Ultrathin Quantum Wells of IrO_{2}. PHYSICAL REVIEW LETTERS 2018; 121:176802. [PMID: 30411938 DOI: 10.1103/physrevlett.121.176802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 05/09/2018] [Indexed: 06/08/2023]
Abstract
The carrier effective mass plays a crucial role in modern electronic, optical, and catalytic devices and is fundamentally related to key properties of solids such as the mobility and density of states. Here we demonstrate a method to deterministically engineer the effective mass using spatial confinement in metallic quantum wells of the transition metal oxide IrO_{2}. Using a combination of in situ angle-resolved photoemission spectroscopy measurements in conjunction with precise synthesis by oxide molecular-beam epitaxy, we show that the low-energy electronic subbands in ultrathin films of rutile IrO_{2} have their effective masses enhanced by up to a factor of 6 with respect to the bulk. The origin of this strikingly large mass enhancement is the confinement-induced quantization of the highly nonparabolic, three-dimensional electronic structure of IrO_{2} in the ultrathin limit. This mechanism lies in contrast to that observed in other transition metal oxides, in which mass enhancement tends to result from complex electron-electron interactions and is difficult to control. Our results demonstrate a general route towards the deterministic enhancement and engineering of carrier effective masses in spatially confined systems, based on an understanding of the three-dimensional bulk electronic structure.
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Affiliation(s)
- Jason K Kawasaki
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA
- Laboratory for Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
- Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - Choong H Kim
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, Korea
| | - Jocienne N Nelson
- Laboratory for Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - Sophie Crisp
- Laboratory for Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - Christian J Zollner
- Department of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - Eric Biegenwald
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - John T Heron
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Craig J Fennie
- Department of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - Darrell G Schlom
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Kyle M Shen
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA
- Laboratory for Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
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83
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Zhang XJ, Liu BG. Strain-driven carrier-type switching of surface two-dimensional electron and hole gases in a KTaO 3 thin film. Phys Chem Chem Phys 2018; 20:24257-24262. [PMID: 30211411 DOI: 10.1039/c8cp03650k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Since the discovery of a two-dimensional (2D) electron gas at the LaAlO3/SrTiO3 interface, 2D carrier gases at such oxide interfaces and surfaces have attracted great attention because they can host many important phenomena and may produce novel functional devices. Here, we show through first-principles investigations that the surface 2D electron and hole gases in a KTaO3 (KTO) thin film can be tuned by applying biaxial stress. When increasing compressive in-plane strain, the 2D carrier concentrations decrease down to zero and then a new pair of surface 2D electron and hole gases appears in which the carrier types are switched to the opposite ones. Our analysis indicates that this carrier-type switching occurs because the increasing compressive strain reverses the slope of monolayer-resolved electrostatic potential along the [001] direction. We also present strain-dependent carrier concentrations and effective masses, and explore their thickness dependence. It is further shown that the 2D carrier gases and their strain-driven carrier-type switching across the KTO layer still remain true in the presence of overlayers and epitaxial substrates. These phenomena should be useful to design novel functional devices.
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Affiliation(s)
- Xue-Jing Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
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84
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Mathieu C, Gonzalez S, Lubin C, Copie O, Feyer V, Schneider CM, Barrett N. High-temperature 2D Fermi surface of SrTiO3
studied by energy-filtered PEEM. SURF INTERFACE ANAL 2018. [DOI: 10.1002/sia.6533] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Claire Mathieu
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
| | - Sara Gonzalez
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
- BaDElPh beamline; Elettra-Sincrotrone Trieste; S.S. 14 km 163.5 in AREA Science Park Basovizza I-34149 Trieste Italy
| | - Christophe Lubin
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
| | - Olivier Copie
- Institut Jean Lamour; UMR 7198 CNRS/Université de Lorraine; Vandoeuvre-lès-Nancy France
| | - Vitaliy Feyer
- Peter Grünberg Institute (PGI-6); JARA-FIT, Research Center Jülich; Jülich Germany
- NanoESCA beamline; Elettra-Sincrotrone Trieste; S.S. 14 km 163.5 in AREA Science Park Basovizza I-34149 Trieste Italy
| | - Claus M. Schneider
- Peter Grünberg Institute (PGI-6); JARA-FIT, Research Center Jülich; Jülich Germany
| | - Nick Barrett
- SPEC, CEA, CNRS; Université Paris-Saclay, CEA Saclay; Gif-sur-Yvette Cedex France
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85
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Ortmann JE, Nookala N, He Q, Gao L, Lin C, Posadas AB, Borisevich AY, Belkin MA, Demkov AA. Quantum Confinement in Oxide Heterostructures: Room-Temperature Intersubband Absorption in SrTiO 3/LaAlO 3 Multiple Quantum Wells. ACS NANO 2018; 12:7682-7689. [PMID: 30052026 DOI: 10.1021/acsnano.8b01293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The Si-compatibility of perovskite heterostructures offers the intriguing possibility of producing oxide-based quantum well (QW) optoelectronic devices for use in Si photonics. While the SrTiO3/LaAlO3 (STO/LAO) system has been studied extensively in the hopes of using the interfacial two-dimensional electron gas in Si-integrated electronics, the potential to exploit its giant 2.4 eV conduction band offset in oxide-based QW optoelectronic devices has so far been largely ignored. Here, we demonstrate room-temperature intersubband absorption in STO/LAO QW heterostructures at energies on the order of hundreds of meV, including at energies approaching the critically important telecom wavelength of 1.55 μm. We demonstrate the ability to control the absorption energy by changing the width of the STO well layers by a single unit cell and present theory showing good agreement with experiment. A detailed structural and chemical analysis of the samples via scanning transmission electron microscopy and electron energy loss spectroscopy is presented. This work represents an important proof-of-concept for the use of transition metal oxide QWs in Si-compatible optoelectronic devices.
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Affiliation(s)
- J Elliott Ortmann
- Department of Physics , The University of Texas , Austin , Texas 78712 , United States
| | - Nishant Nookala
- Department of Electrical and Computer Engineering , The University of Texas , Austin , Texas 78712 , United States
- Microelectronics Research Center , The University of Texas at Austin , Austin , Texas 78758 , United States
| | - Qian He
- The Materials Science and Technology Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Lingyuan Gao
- Department of Physics , The University of Texas , Austin , Texas 78712 , United States
| | - Chungwei Lin
- Department of Physics , The University of Texas , Austin , Texas 78712 , United States
- Mitsubishi Electric Research Laboratories , Cambridge , Massachusetts 02139 , United States
| | - Agham B Posadas
- Department of Physics , The University of Texas , Austin , Texas 78712 , United States
| | - Albina Y Borisevich
- The Materials Science and Technology Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Mikhail A Belkin
- Department of Electrical and Computer Engineering , The University of Texas , Austin , Texas 78712 , United States
- Microelectronics Research Center , The University of Texas at Austin , Austin , Texas 78758 , United States
| | - Alexander A Demkov
- Department of Physics , The University of Texas , Austin , Texas 78712 , United States
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86
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Mechanical dissipation from charge and spin transitions in oxygen-deficient SrTiO 3 surfaces. Nat Commun 2018; 9:2946. [PMID: 30054477 PMCID: PMC6063934 DOI: 10.1038/s41467-018-05392-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 06/26/2018] [Indexed: 11/15/2022] Open
Abstract
Bodies in relative motion separated by a gap of a few nanometers can experience a tiny friction force. This non-contact dissipation can have various origins and can be successfully measured by a sensitive pendulum atomic force microscope tip oscillating laterally above the surface. Here, we report on the observation of dissipation peaks at selected voltage-dependent tip-surface distances for oxygen-deficient strontium titanate (SrTiO3) surface at low temperatures (T = 5 K). The observed dissipation peaks are attributed to tip-induced charge and spin state transitions in quantum-dot-like entities formed by single oxygen vacancies (and clusters thereof, possibly through a collective mechanism) at the SrTiO3 surface, which in view of technological and fundamental research relevance of the material opens important avenues for further studies and applications. Non-contact atomic force microscope (AFM) dissipation contains rich information on the electron, phonon and spin states, but has been poorly understood. Here the authors demonstrated that tip-induced charge and spin state transitions in oxygen vacancies at SrTiO3 surface are revealed by AFM dissipation measurements.
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87
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Sopiha KV, Malyi OI, Persson C, Wu P. Suppression of surfaces states at cubic perovskite (001) surfaces by CO 2 adsorption. Phys Chem Chem Phys 2018; 20:18828-18836. [PMID: 29964284 DOI: 10.1039/c8cp02535e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
By using first-principles approach, the interaction of CO2 with (001) surfaces of six cubic ABO3 perovskites (A = Ba, Sr and B = Ti, Zr, Hf) is studied in detail. We show that CO2 adsorption results in the formation of highly stable CO3-like complexes with similar geometries for all investigated compounds. This reaction leads to the suppression of the surfaces states, opening the band gaps of the slab systems up to the corresponding bulk energy limits. For most AO-terminated ABO3(001) perovskite surfaces, a CO2 coverage of 0.25 was found to be sufficient to fully suppress the surface states, whereas the same effect can only be achieved at 0.50 CO2 coverage for the BO2-terminated surfaces. The largest band gap modulation among the AO-terminated surfaces was found for SrHfO3(001) and BaHfO3(001), whereas the most profound effect among the BO2-terminated surfaces was identified for SrTiO3(001) and BaTiO3(001). Based on these results and considering practical difficulties associated with measuring conductivity of highly resistive materials, TiO2-terminated SrTiO3(001) and BaTiO3(001) were identified as the most prospective candidates for chemiresistive CO2 sensing applications.
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Affiliation(s)
- Kostiantyn V Sopiha
- Entropic Interface Group, Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore, Singapore.
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88
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Zhou G, Zhang Q, Zheng F, Zhang D, Liu C, Wang X, Song CL, He K, Ma XC, Gu L, Zhang P, Wang L, Xue QK. Interface enhanced superconductivity in monolayer FeSe films on MgO(001): charge transfer with atomic substitution. Sci Bull (Beijing) 2018; 63:747-752. [PMID: 36658947 DOI: 10.1016/j.scib.2018.05.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Revised: 05/15/2018] [Accepted: 05/17/2018] [Indexed: 01/21/2023]
Abstract
Interface enhanced superconductivity over 50 K has been discovered in monolayer FeSe films grown on several TiO2-terminated oxide substrates. Whether such phenomenon exists in other oxide substrates remains an extremely interesting topic. Here we report enhanced superconductivity with an onset transition temperature of 18 K in monolayer FeSe on MgO(001) substrate by transport measurement. Scanning transmission electron microscopy investigation on the interface structure indicates that FeSe films grow epitaxially on MgO(001) and that overlayer Fe atoms diffuse into the top two layers of MgO and substitute Mg atoms. Our density functional theory calculations reveal that this substitution promotes the charge transfer from the MgO substrate to the FeSe films, an essential process that also occurs in monolayer FeSe on TiO2-terminated oxides and contributes to the enhanced superconductivity therein. Our finding suggests that superconductivity enhancement in monolayer FeSe films on oxides substrates is rather general as long as charge transfer is allowed at the interface, thus pointing out an explicit direction for searching for new high temperature superconductivity by interface engineering.
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Affiliation(s)
- Guanyu Zhou
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Qinghua Zhang
- Laboratory for Advanced Materials & Electron Microscopy, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Fawei Zheng
- Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
| | - Ding Zhang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Chong Liu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xiaoxiao Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Can-Li Song
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Ke He
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Xu-Cun Ma
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Lin Gu
- Laboratory for Advanced Materials & Electron Microscopy, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
| | - Ping Zhang
- Institute of Applied Physics and Computational Mathematics, Beijing 100088, China.
| | - Lili Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
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89
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Casals B, Schiaffino A, Casiraghi A, Hämäläinen SJ, López González D, van Dijken S, Stengel M, Herranz G. Low-Temperature Dielectric Anisotropy Driven by an Antiferroelectric Mode in SrTiO_{3}. PHYSICAL REVIEW LETTERS 2018; 120:217601. [PMID: 29883130 DOI: 10.1103/physrevlett.120.217601] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 01/09/2018] [Indexed: 06/08/2023]
Abstract
Strontium titanate (SrTiO_{3}) is the quintessential material for oxide electronics. One of its hallmark features is the transition, driven by antiferrodistortive (AFD) lattice modes, from a cubic to a ferroelastic low-temperature phase. Here we investigate the evolution of the ferroelastic twin walls upon application of an electric field. Remarkably, we find that the dielectric anisotropy of tetragonal SrTiO_{3}, rather than the intrinsic domain wall polarity, is the main driving force for the motion of the twins. Based on a combined first-principles and Landau-theory analysis, we show that such anisotropy is dominated by a trilinear coupling between the polarization, the AFD lattice tilts, and a previously overlooked antiferroelectric (AFE) mode. We identify the latter AFE phonon with the so-called "R mode" at ∼440 cm^{-1}, which was previously detected in IR experiments, but whose microscopic nature was unknown.
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Affiliation(s)
- Blai Casals
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
| | - Andrea Schiaffino
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
| | - Arianna Casiraghi
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
| | - Sampo J Hämäläinen
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
| | - Diego López González
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
| | - Sebastiaan van Dijken
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
| | - Massimiliano Stengel
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys, 23, 08010 Barcelona, Catalonia, Spain
| | - Gervasi Herranz
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
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90
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Fan L, Wang X, Wang F, Zhang Q, Zhu L, Meng Q, Wang B, Zhang Z, Zou C. Revealing the role of oxygen vacancies on the phase transition of VO 2 film from the optical-constant measurements. RSC Adv 2018; 8:19151-19156. [PMID: 35539638 PMCID: PMC9080608 DOI: 10.1039/c8ra03292k] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 05/18/2018] [Indexed: 11/21/2022] Open
Abstract
Vanadium dioxide (VO2) material shows a distinct metal–insulator transition (MIT) at the critical temperature of ∼340 K. Similar to other correlated oxides, the MIT properties of VO2 is always sensitive to those crystal defects such as oxygen vacancies. In this study, we investigated the oxygen vacancies related phase transition behavior of VO2 crystal film and systematically examined the effect of oxygen vacancies from the optical constant measurements. The results indicated that the oxygen vacancies changed not only the electron occupancy on V 3d–O 2p hybrid-orbitals, but also the electron–electron correlation energy and the related band gap, which modulated the MIT behavior and decreased the critical temperature resultantly. Our work not only provided a facile way to modulate the MIT behavior of VO2 crystal film, but also revealed the effects of the oxygen vacancies on the electronic inter-band transitions as well as the electronic correlations in driving this MIT process. Optical conductivity spectroscopy was performed to reveal the role of oxygen vacancies during VO2 metal–insulator transition.![]()
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Affiliation(s)
- Lele Fan
- Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology Yancheng 224051 P. R. China .,National Synchrotron Radiation Laboratory, University of Science and Technology of China Hefei 230029 P. R. China
| | - Xiangqi Wang
- Department of Physics, University of Science and Technology of China Hefei 230026 P. R. China
| | - Feng Wang
- Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology Yancheng 224051 P. R. China
| | - Qinfang Zhang
- Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology Yancheng 224051 P. R. China
| | - Lei Zhu
- Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology Yancheng 224051 P. R. China
| | - Qiangqiang Meng
- Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology Yancheng 224051 P. R. China
| | - Baolin Wang
- School of Physical Science and Technology, Nanjing Normal University Nanjing 210023 P. R. China
| | - Zengming Zhang
- Department of Physics, University of Science and Technology of China Hefei 230026 P. R. China
| | - Chongwen Zou
- National Synchrotron Radiation Laboratory, University of Science and Technology of China Hefei 230029 P. R. China
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91
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Kubacki J, Kajewski D, Goraus J, Szot K, Koehl A, Lenser C, Dittmann R, Szade J. Impact of Fe doping on the electronic structure of SrTiO3 thin films determined by resonant photoemission. J Chem Phys 2018; 148:154702. [DOI: 10.1063/1.5007928] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- J. Kubacki
- A. Chełkowski Institute of Physics, University of Silesia, Katowice 40-007, Poland
- Silesian Center for Education and Interdisciplinary Research, Chorzów, Poland
| | - D. Kajewski
- A. Chełkowski Institute of Physics, University of Silesia, Katowice 40-007, Poland
| | - J. Goraus
- A. Chełkowski Institute of Physics, University of Silesia, Katowice 40-007, Poland
- Silesian Center for Education and Interdisciplinary Research, Chorzów, Poland
| | - K. Szot
- A. Chełkowski Institute of Physics, University of Silesia, Katowice 40-007, Poland
- Peter Grünberg Institut, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - A. Koehl
- Peter Grünberg Institut, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Ch. Lenser
- Peter Grünberg Institut, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - R. Dittmann
- Peter Grünberg Institut, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - J. Szade
- A. Chełkowski Institute of Physics, University of Silesia, Katowice 40-007, Poland
- Silesian Center for Education and Interdisciplinary Research, Chorzów, Poland
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92
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Zhao W, Li M, Chang CZ, Jiang J, Wu L, Liu C, Moodera JS, Zhu Y, Chan MHW. Direct imaging of electron transfer and its influence on superconducting pairing at FeSe/SrTiO 3 interface. SCIENCE ADVANCES 2018; 4:eaao2682. [PMID: 29556528 PMCID: PMC5856486 DOI: 10.1126/sciadv.aao2682] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Accepted: 02/07/2018] [Indexed: 05/31/2023]
Abstract
The exact mechanism responsible for the significant enhancement of the superconducting transition temperature (Tc) of monolayer iron selenide (FeSe) films on SrTiO3 (STO) over that of bulk FeSe is an open issue. We present the results of a coordinated study of electrical transport, low temperature electron energy-loss spectroscopy (EELS), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements on FeSe/STO films of different thicknesses. HAADF-STEM imaging together with EELS mapping across the FeSe/STO interface shows direct evidence of electrons transferred from STO to the FeSe layer. The transferred electrons were found to accumulate within the first two atomic layers of the FeSe films near the STO substrate. An additional Se layer is also resolved to reside between the FeSe film and the TiO x -terminated STO substrate. Our transport results found that a positive backgate applied from STO is particularly effective in enhancing Tc of the films while minimally changing the carrier density. This increase in Tc is due to the positive backgate that "pulls" the transferred electrons in FeSe films closer to the interface and thus enhances their coupling to interfacial phonons and also the electron-electron interaction within FeSe films.
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Affiliation(s)
- Weiwei Zhao
- Center for Nanoscale Science and Department of Physics, Pennsylvania State University, University Park, PA 16802–6300, USA
- State Key Laboratory of Advanced Welding and Joining and Research Center of Flexible Printed Electronic Technology, Harbin Institute of Technology, Shenzhen 518055, People’s Republic of China
| | - Mingda Li
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Francis Bitter Magnet Laboratory and Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Cui-Zu Chang
- Center for Nanoscale Science and Department of Physics, Pennsylvania State University, University Park, PA 16802–6300, USA
- Francis Bitter Magnet Laboratory and Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jue Jiang
- Center for Nanoscale Science and Department of Physics, Pennsylvania State University, University Park, PA 16802–6300, USA
| | - Lijun Wu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Chaoxing Liu
- Center for Nanoscale Science and Department of Physics, Pennsylvania State University, University Park, PA 16802–6300, USA
| | - Jagadeesh S. Moodera
- Francis Bitter Magnet Laboratory and Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Yimei Zhu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Moses H. W. Chan
- Center for Nanoscale Science and Department of Physics, Pennsylvania State University, University Park, PA 16802–6300, USA
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93
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Pai YY, Tylan-Tyler A, Irvin P, Levy J. Physics of SrTiO 3-based heterostructures and nanostructures: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2018; 81:036503. [PMID: 29424362 DOI: 10.1088/1361-6633/aa892d] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
This review provides a summary of the rich physics expressed within SrTiO3-based heterostructures and nanostructures. The intended audience is researchers who are working in the field of oxides, but also those with different backgrounds (e.g., semiconductor nanostructures). After reviewing the relevant properties of SrTiO3 itself, we will then discuss the basics of SrTiO3-based heterostructures, how they can be grown, and how devices are typically fabricated. Next, we will cover the physics of these heterostructures, including their phase diagram and coupling between the various degrees of freedom. Finally, we will review the rich landscape of quantum transport phenomena, as well as the devices that elicit them.
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Affiliation(s)
- Yun-Yi Pai
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, United States of America. Pittsburgh Quantum Institute, Pittsburgh, PA 15260, United States of America
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94
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Setvin M, Reticcioli M, Poelzleitner F, Hulva J, Schmid M, Boatner LA, Franchini C, Diebold U. Polarity compensation mechanisms on the perovskite surface KTaO
3
(001). Science 2018; 359:572-575. [DOI: 10.1126/science.aar2287] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 12/19/2017] [Indexed: 11/02/2022]
Affiliation(s)
- Martin Setvin
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
| | - Michele Reticcioli
- University of Vienna, Faculty of Physics and Center for Computational Materials Science, Vienna, Austria
| | - Flora Poelzleitner
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
| | - Jan Hulva
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
| | - Michael Schmid
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
| | - Lynn A. Boatner
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Cesare Franchini
- University of Vienna, Faculty of Physics and Center for Computational Materials Science, Vienna, Austria
| | - Ulrike Diebold
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
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95
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Sopiha KV, Malyi OI, Persson C, Wu P. Band gap modulation of SrTiO 3 upon CO 2 adsorption. Phys Chem Chem Phys 2018; 19:16629-16637. [PMID: 28620658 DOI: 10.1039/c7cp01462g] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Herein, CO2 chemisorption on SrTiO3(001) surfaces is studied using ab initio calculations to establish new chemical sensing mechanisms. It was found that CO2 adsorption opens the band gap of the material. However, the mechanisms are different: the CO2 adsorption on the TiO2-terminated surface neutralizes the surface states at the valence band (VB) maximum, whereas for the SrO-terminated surface it suppresses the conduction band (CB) minimum. For the TiO2-terminated surface, the effect is explained by the passivation of dangling bonds, whereas for the SrO-terminated surface, the suppression is caused by surface relaxation. Modulation of the VB states implies a more direct change in charge distribution, and thus, the induced change in the band gap is more prominent at the TiO2 termination. Further, it has been shown that both CO2 adsorption energy and surface band gap are strongly dependent on CO2 coverage, suggesting that the observed effect can be utilized in sensing applications for a wide range of CO2 concentrations.
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Affiliation(s)
- Kostiantyn V Sopiha
- Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore, Singapore.
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96
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Zhou F, Liu Y, Lai Z, Liao M, Zhou Y, Huang Y, Zhu J. Quantum confined two-dimensional electron/hole gas switching by facet orientation of perovskite oxides. RSC Adv 2018; 8:20477-20482. [PMID: 35542364 PMCID: PMC9080832 DOI: 10.1039/c8ra03928c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 05/29/2018] [Indexed: 11/21/2022] Open
Abstract
The Polar discontinuity at heterointerface and the bare surface reconstructs the electronic phase of perovskite oxides.
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Affiliation(s)
- Fei Zhou
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage
| | - Yong Liu
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
- National Key Laboratory for Precision Hot Processing of Metals
| | - Zhonghong Lai
- Analysis and Testing Center
- Harbin Institute of Technology
- Harbin
- China
| | - Mingqing Liao
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
| | - Yi Zhou
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
| | - Yudong Huang
- MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology
- Harbin
- China
| | - Jingchuan Zhu
- School of Materials Science and Engineering
- Harbin Institute of Technology
- Harbin
- China
- National Key Laboratory of Science and Technology on Advanced Composites in Special Environments
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97
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Mawrie A, Verma S, Ghosh TK. Electrical and thermoelectric transport properties of two-dimensional fermionic systems with k-cubic spin-orbit coupling. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:465303. [PMID: 29067916 DOI: 10.1088/1361-648x/aa89b9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We investigate the effect of k-cubic spin-orbit interaction on the electrical and thermoelectric transport properties of two-dimensional fermionic systems. We obtain exact analytical expressions of the inverse relaxation time (IRT) and the Drude conductivity for long-range Coulomb and short-range delta scattering potentials. The IRT reveals that the scattering is completely suppressed along the three directions [Formula: see text] with [Formula: see text]. We also obtain analytical results of the thermopower and thermal conductivity at low temperature. The thermoelectric transport coefficients obey the Wiedemann-Franz law, even in the presence of k-cubic Rashba spin-orbit interaction (RSOI) at low temperature. In the presence of a quantizing magnetic field, the signature of the RSOI is revealed through the appearance of the beating pattern in the Shubnikov-de Haas (SdH) oscillations of thermopower and thermal conductivity in the low magnetic field regime. The empirical formulae for the SdH oscillation frequencies accurately describe the locations of the beating nodes. The beating pattern in magnetothermoelectric measurement can be used to extract the spin-orbit coupling constant.
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Affiliation(s)
- Alestin Mawrie
- Department of Physics, Indian Institute of Technology-Kanpur, Kanpur-208 016, India
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98
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Niu W, Zhang Y, Gan Y, Christensen DV, Soosten MV, Garcia-Suarez EJ, Riisager A, Wang X, Xu Y, Zhang R, Pryds N, Chen Y. Giant Tunability of the Two-Dimensional Electron Gas at the Interface of γ-Al 2O 3/SrTiO 3. NANO LETTERS 2017; 17:6878-6885. [PMID: 28968124 DOI: 10.1021/acs.nanolett.7b03209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Two-dimensional electron gases (2DEGs) formed at the interface between two oxide insulators provide a rich platform for the next generation of electronic devices. However, their high carrier density makes it rather challenging to control the interface properties under a low electric field through a dielectric solid insulator, that is, in the configuration of conventional field-effect transistors. To surpass this long-standing limit, we used ionic liquids as the dielectric layer for electrostatic gating of oxide interfaces in an electric double layer transistor (EDLT) configuration. Herein, we reported giant tunability of the physical properties of 2DEGs at the spinel/perovskite interface of γ-Al2O3/SrTiO3 (GAO/STO). By modulating the carrier density thus the band filling with ionic-liquid gating, the system experiences a Lifshitz transition at a critical carrier density of 3.0 × 1013 cm-2, where a remarkably strong enhancement of Rashba spin-orbit interaction and an emergence of Kondo effect at low temperatures are observed. Moreover, as the carrier concentration depletes with decreasing gating voltage, the electron mobility is enhanced by more than 6 times in magnitude, leading to the observation of clear quantum oscillations. The great tunability of GAO/STO interface by EDLT gating not only shows promise for design of oxide devices with on-demand properties but also sheds new light on the electronic structure of 2DEG at the nonisostructural spinel/perovskite interface.
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Affiliation(s)
- Wei Niu
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø Campus, 4000 Roskilde, Denmark
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, Nanjing University , 210093 Nanjing, China
| | - Yu Zhang
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø Campus, 4000 Roskilde, Denmark
| | - Yulin Gan
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø Campus, 4000 Roskilde, Denmark
| | - Dennis V Christensen
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø Campus, 4000 Roskilde, Denmark
| | - Merlin V Soosten
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø Campus, 4000 Roskilde, Denmark
| | - Eduardo J Garcia-Suarez
- Center for Catalysis and Sustainable Chemistry, Department of Chemistry, Technical University of Denmark , 2800 Lyngby, Denmark
| | - Anders Riisager
- Center for Catalysis and Sustainable Chemistry, Department of Chemistry, Technical University of Denmark , 2800 Lyngby, Denmark
| | - Xuefeng Wang
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, Nanjing University , 210093 Nanjing, China
| | - Yongbing Xu
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, Nanjing University , 210093 Nanjing, China
| | - Rong Zhang
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, Nanjing University , 210093 Nanjing, China
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø Campus, 4000 Roskilde, Denmark
| | - Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark , Risø Campus, 4000 Roskilde, Denmark
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99
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Kolasiński K, Sellier H, Szafran B. Extraction of the Rashba spin-orbit coupling constant from scanning gate microscopy conductance maps for quantum point contacts. Sci Rep 2017; 7:14935. [PMID: 29097691 PMCID: PMC5668439 DOI: 10.1038/s41598-017-14380-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 10/09/2017] [Indexed: 11/09/2022] Open
Abstract
We study the possibility for the extraction of the Rashba spin-orbit coupling constant for a two-dimensional electron gas with the conductance microscopy technique. Due to the interplay between the effective magnetic field due to the Rashba spin-orbit coupling and the external magnetic field applied within the plane of confinement, the electron backscattering induced by a charged tip of an atomic force microscope located above the sample leads to the spin precession and spin mixing of the incident and reflected electron waves between the QPC and the tip-induced 2DEG depletion region. This mixing leads to a characteristic angle-dependent beating pattern visible in the conductance maps. We show that the structure of the Fermi level, bearing signatures of the spin-orbit coupling, can be extracted from the Fourier transform of the interference fringes in the conductance maps as a function of the magnetic field direction. We propose a simple analytical model which can be used to fit the experimental data in order to obtain the spin-orbit coupling constant.
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Affiliation(s)
- K Kolasiński
- AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059, Kraków, Poland
| | - H Sellier
- Université Grenoble Alpes, CNRS, Institut Néel, 38000, Grenoble, France
| | - B Szafran
- AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059, Kraków, Poland.
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100
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Plumb NC, Radović M. Angle-resolved photoemission spectroscopy studies of metallic surface and interface states of oxide insulators. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:433005. [PMID: 28961143 DOI: 10.1088/1361-648x/aa833f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Over the last decade, conducting states embedded in insulating transition metal oxides (TMOs) have served as gateways to discovering and probing surprising phenomena that can emerge in complex oxides, while also opening opportunities for engineering advanced devices. These states are commonly realized at thin film interfaces, such as the well-known case of LaAlO3 (LAO) grown on SrTiO3 (STO). In recent years, the use of angle-resolved photoemission spectroscopy (ARPES) to investigate the k-space electronic structure of such materials led to the discovery that metallic states can also be formed on the bare surfaces of certain TMOs. In this topical review, we report on recent studies of low-dimensional metallic states confined at insulating oxide surfaces and interfaces as seen from the perspective of ARPES, which provides a direct view of the occupied band structure. While offering a fairly broad survey of progress in the field, we draw particular attention to STO, whose surface is so far the best-studied, and whose electronic structure is probably of the most immediate interest, given the ubiquitous use of STO substrates as the basis for conducting oxide interfaces. The ARPES studies provide crucial insights into the electronic band structure, orbital character, dimensionality/confinement, spin structure, and collective excitations in STO surfaces and related oxide surface/interface systems. The obtained knowledge increases our understanding of these complex materials and gives new perspectives on how to manipulate their properties.
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Affiliation(s)
- Nicholas C Plumb
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
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