1
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Zhou Y, Waelchli A, Boselli M, Crassee I, Bercher A, Luo W, Duan J, van Mechelen JLM, van der Marel D, Teyssier J, Rischau CW, Korosec L, Gariglio S, Triscone JM, Kuzmenko AB. Thermal and electrostatic tuning of surface phonon-polaritons in LaAlO 3/SrTiO 3 heterostructures. Nat Commun 2023; 14:7686. [PMID: 38001108 PMCID: PMC10673882 DOI: 10.1038/s41467-023-43464-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2022] [Accepted: 11/10/2023] [Indexed: 11/26/2023] Open
Abstract
Phonon polaritons are promising for infrared applications due to a strong light-matter coupling and subwavelength energy confinement they offer. Yet, the spectral narrowness of the phonon bands and difficulty to tune the phonon polariton properties hinder further progress in this field. SrTiO3 - a prototype perovskite oxide - has recently attracted attention due to two prominent far-infrared phonon polaritons bands, albeit without any tuning reported so far. Here we show, using cryogenic infrared near-field microscopy, that long-propagating surface phonon polaritons are present both in bare SrTiO3 and in LaAlO3/SrTiO3 heterostructures hosting a two-dimensional electron gas. The presence of the two-dimensional electron gas increases dramatically the thermal variation of the upper limit of the surface phonon polariton band due to temperature dependent polaronic screening of the surface charge carriers. Furthermore, we demonstrate a tunability of the upper surface phonon polariton frequency in LaAlO3/SrTiO3 via electrostatic gating. Our results suggest that oxide interfaces are a new platform bridging unconventional electronics and long-wavelength nanophotonics.
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Affiliation(s)
- Yixi Zhou
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
- Beijing Key Laboratory of Nano-Photonics and Nano-Structure (NPNS), Department of Physics, Capital Normal University, 100048, Beijing, China
| | - Adrien Waelchli
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
| | - Margherita Boselli
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
| | - Iris Crassee
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
| | - Adrien Bercher
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
| | - Weiwei Luo
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
- The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics and TEDA Applied Physics Institute, Nankai University, Tianjin, 300457, China
| | - Jiahua Duan
- Department of Physics, University of Oviedo, Oviedo, 33006, Spain
| | - J L M van Mechelen
- Department of Electrical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven, Netherlands
| | - Dirk van der Marel
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
| | - Jérémie Teyssier
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
| | - Carl Willem Rischau
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
| | - Lukas Korosec
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
| | - Stefano Gariglio
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
| | - Jean-Marc Triscone
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland
| | - Alexey B Kuzmenko
- Department of Quantum Matter Physics, University of Geneva, CH-1211, Geneva, 4, Switzerland.
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2
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Occhicone A, Polito R, Michelotti F, Ortolani M, Baldassarre L, Pea M, Sinibaldi A, Notargiacomo A, Cibella S, Mattioli F, Roy P, Brubach JB, Calvani P, Nucara A. Low-Temperature Stability and Sensing Performance of Mid-Infrared Bloch Surface Waves on a One-Dimensional Photonic Crystal. ACS APPLIED MATERIALS & INTERFACES 2022; 14:43853-43860. [PMID: 36106792 PMCID: PMC9523610 DOI: 10.1021/acsami.2c07894] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 09/07/2022] [Indexed: 05/27/2023]
Abstract
The growing need for new and reliable surface sensing methods is arousing interest in the electromagnetic excitations of ultrathin films, i.e., to generate electromagnetic field distributions that resonantly interact with the most significant quasi-particles of condensed matter. In such a context, Bloch surface waves turned out to be a valid alternative to surface plasmon polaritons to implement high-sensitivity sensors in the visible spectral range. Only in the last few years, however, has their use been extended to infrared wavelengths, which represent a powerful tool for detecting and recognizing molecular species and crystalline structures. In this work, we demonstrate, by means of high-resolution reflectivity measurements, that a one-dimensional photonic crystal can sustain Bloch surface waves in the infrared spectral range from room temperature down to 10 K. To the best of our knowledge, this is the first demonstration of infrared Bloch surface waves at cryogenic temperatures. Furthermore, by exploiting the enhancement of the surface state and the high brilliance of infrared synchrotron radiation, we demonstrate that the proposed BSW-based sensor has a sensitivity on the order of 2.9 cm-1 for each nanometer-thick ice layer grown on its surface below 150 K. In conclusion, we believe that Bloch surface wave-based sensors are a valid new class of surface mode-based sensors for applications in materials science.
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Affiliation(s)
- Agostino Occhicone
- Department
of Basic and Applied Sciences for Engineering, Sapienza University of Rome, via A. Scarpa, 16, 00161 Roma, Italy
| | - Raffaella Polito
- Department
of Physics, Sapienza University of Rome, Piazzale A. Moro, 5, 00185 Roma, Italy
| | - Francesco Michelotti
- Department
of Basic and Applied Sciences for Engineering, Sapienza University of Rome, via A. Scarpa, 16, 00161 Roma, Italy
| | - Michele Ortolani
- Department
of Physics, Sapienza University of Rome, Piazzale A. Moro, 5, 00185 Roma, Italy
| | - Leonetta Baldassarre
- Department
of Physics, Sapienza University of Rome, Piazzale A. Moro, 5, 00185 Roma, Italy
| | - Marialilia Pea
- CNR-IFN, Via del Fosso
del Cavaliere, 100, 00133 Roma, Italy
| | - Alberto Sinibaldi
- Department
of Basic and Applied Sciences for Engineering, Sapienza University of Rome, via A. Scarpa, 16, 00161 Roma, Italy
| | | | - Sara Cibella
- CNR-IFN, Via del Fosso
del Cavaliere, 100, 00133 Roma, Italy
| | | | - Pascale Roy
- Synchrotron
SOLEIL, L’Orme des Merisiers,
Saint-Aubin, Gif-sur-Yvette Cedex F-91192, France
| | - Jean-Blaise Brubach
- Synchrotron
SOLEIL, L’Orme des Merisiers,
Saint-Aubin, Gif-sur-Yvette Cedex F-91192, France
| | - Paolo Calvani
- Department
of Physics, Sapienza University of Rome, Piazzale A. Moro, 5, 00185 Roma, Italy
| | - Alessandro Nucara
- CNR-SPIN
and Department of Physics, Sapienza University
of Rome, Piazzale A.
Moro, 5, 00185 Roma, Italy
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3
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Chapman KS, Atkinson WA. Modified transverse Ising model for the dielectric properties of SrTiO 3 films and interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:065303. [PMID: 31634883 DOI: 10.1088/1361-648x/ab4fa7] [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 transverse Ising model (TIM), with pseudospins representing the lattice polarization, is often used as a simple description of ferroelectric materials. However, we demonstrate that the TIM, as it is usually formulated, provides an incorrect description of SrTiO3 films and interfaces because of its inadequate treatment of spatial inhomogeneity. We correct this deficiency by adding a pseudospin anisotropy to the model. We demonstrate the physical need for this term by comparison of the TIM to a typical Landau-Ginzburg-Devonshire model. We then demonstrate the physical consequences of the modification for two model systems: a ferroelectric thin film, and a metallic LaAlO3/SrTiO3 interface. We show that, in both cases, the modified TIM has a substantially different polarization profile than the conventional TIM. In particular, at low temperatures the formation of quantized states at LaAlO3/SrTiO3 interfaces only occurs in the modified TIM.
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Affiliation(s)
- Kelsey S Chapman
- Department of Physics and Astronomy, Trent University, Peterborough, Ontario, K9L 0G2, Canada
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4
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Verseils M, Voute A, Langerome B, Deutsch M, Brubach JB, Kalaboukhov A, Nucara A, Calvani P, Roy P. Grazing-angle reflectivity setup for the low-temperature infrared spectroscopy of two-dimensional systems. JOURNAL OF SYNCHROTRON RADIATION 2019; 26:1945-1950. [PMID: 31721739 DOI: 10.1107/s1600577519010920] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 08/04/2019] [Indexed: 06/10/2023]
Abstract
A new optical setup is described that allows the reflectivity at grazing incidence to be measured, including ultrathin films and two-dimensional electron systems (2DES) down to liquid-helium temperatures, by exploiting the Berreman effect and the high brilliance of infrared synchrotron radiation. This apparatus is well adapted to detect the absorption of a 2DES of nanometric thickness, namely that which forms spontaneously at the interface between a thin film of LaAlO3 and its SrTiO3 substrate, and to determine its Drude parameters.
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Affiliation(s)
| | | | | | - Maxime Deutsch
- Synchrotron SOLEIL, St Aubin, 91192 Gif-sur-Yvette, France
| | | | - Alexei Kalaboukhov
- Department of Microtechnology and Nanoscience, Chalmers University, S-41296 Gothenburg, Sweden
| | - Alessandro Nucara
- CNR-SPIN and Dipartimento di Fisica, Università di Roma La Sapienza, 00185 Roma, Italy
| | - Paolo Calvani
- CNR-SPIN and Dipartimento di Fisica, Università di Roma La Sapienza, 00185 Roma, Italy
| | - Pascale Roy
- Synchrotron SOLEIL, St Aubin, 91192 Gif-sur-Yvette, France
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5
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Luo W, Boselli M, Poumirol JM, Ardizzone I, Teyssier J, van der Marel D, Gariglio S, Triscone JM, Kuzmenko AB. High sensitivity variable-temperature infrared nanoscopy of conducting oxide interfaces. Nat Commun 2019; 10:2774. [PMID: 31235858 PMCID: PMC6591405 DOI: 10.1038/s41467-019-10672-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 05/21/2019] [Indexed: 11/09/2022] Open
Abstract
Probing the local transport properties of two-dimensional electron systems (2DES) confined at buried interfaces requires a non-invasive technique with a high spatial resolution operating in a broad temperature range. In this paper, we investigate the scattering-type scanning near field optical microscopy as a tool for studying the conducting LaAlO3/SrTiO3 interface from room temperature down to 6 K. We show that the near-field optical signal, in particular its phase component, is highly sensitive to the transport properties of the electron system present at the interface. Our modeling reveals that such sensitivity originates from the interaction of the AFM tip with coupled plasmon-phonon modes with a small penetration depth. The model allows us to quantitatively correlate changes in the optical signal with the variation of the 2DES transport properties induced by cooling and by electrostatic gating. To probe the spatial resolution of the technique, we image conducting nano-channels written in insulating heterostructures with a voltage-biased tip of an atomic force microscope.
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Affiliation(s)
- Weiwei Luo
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Margherita Boselli
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Jean-Marie Poumirol
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Ivan Ardizzone
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Jérémie Teyssier
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Dirk van der Marel
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Stefano Gariglio
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Jean-Marc Triscone
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland
| | - Alexey B Kuzmenko
- Department of Quantum Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, 1211, Geneva, Switzerland.
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6
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Falsetti E, Nucara A, Shibayev PP, Salehi M, Moon J, Oh S, Brubach JB, Roy P, Ortolani M, Calvani P. Infrared Spectroscopy of the Topological Surface States of Bi_{2}Se_{3} by Use of the Berreman Effect. PHYSICAL REVIEW LETTERS 2018; 121:176803. [PMID: 30411918 DOI: 10.1103/physrevlett.121.176803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Indexed: 06/08/2023]
Abstract
The Berreman effect (BE) allows one to study the electrodynamics of ultrathin conducting films at the surface of dielectrics by use of grazing-angle infrared spectroscopy and polarized radiation. Here, we first apply the BE to the two-dimensional electron system (2DES) at the interface between a high-purity film of the topological insulator Bi_{2}Se_{3} and its sapphire substrate. We determine for the 2DES a charge density n_{s}=(8±1)×10^{12} cm^{-2}, a thickness d=0.6±0.2 nm, and a mobility μ^{IR}=290±30 cm^{2}/V s. Within errors, all of these parameters result in being independent of temperature between 300 and 10 K. These findings consistently indicate that the 2DES is formed by topological surface states, whose infrared response is then directly observed here.
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Affiliation(s)
- Enrico Falsetti
- Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale Aldo Moro 2, I-00185 Roma, Italy
| | - Alessandro Nucara
- Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale Aldo Moro 2, I-00185 Roma, Italy
| | - Pavel P Shibayev
- Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, New Jersey 08854, USA
| | - Maryam Salehi
- Department of Materials Science and Engineering, Rutgers, the State University of New Jersey, Piscataway, New Jersey 08854, USA
| | - Jisoo Moon
- Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, New Jersey 08854, USA
| | - Seongshik Oh
- Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, New Jersey 08854, USA
| | - Jean-Blaise Brubach
- Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex, France
| | - Pascale Roy
- Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex, France
| | - Michele Ortolani
- Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale Aldo Moro 2, I-00185 Roma, Italy
| | - Paolo Calvani
- Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale Aldo Moro 2, I-00185 Roma, Italy
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7
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Li D, Lemal S, Gariglio S, Wu Z, Fête A, Boselli M, Ghosez P, Triscone J. Probing Quantum Confinement and Electronic Structure at Polar Oxide Interfaces. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2018; 5:1800242. [PMID: 30128239 PMCID: PMC6097152 DOI: 10.1002/advs.201800242] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 04/28/2018] [Indexed: 06/08/2023]
Abstract
Polar discontinuities occurring at interfaces between two materials constitute both a challenge and an opportunity in the study and application of a variety of devices. In order to cure the large electric field occurring in such structures, a reconfiguration of the charge landscape sets in at the interface via chemical modifications, adsorbates, or charge transfer. In the latter case, one may expect a local electronic doping of one material: one example is the two-dimensional electron liquid (2DEL) appearing in SrTiO3 once covered by a polar LaAlO3 layer. Here, it is shown that tuning the formal polarization of a (La,Al)1-x (Sr,Ti) x O3 (LASTO:x) overlayer modifies the quantum confinement of the 2DEL in SrTiO3 and its electronic band structure. The analysis of the behavior in magnetic field of superconducting field-effect devices reveals, in agreement with ab initio calculations and self-consistent Poisson-Schrödinger modeling, that quantum confinement and energy splitting between electronic bands of different symmetries strongly depend on the interface total charge densities. These results strongly support the polar discontinuity mechanisms with a full charge transfer to explain the origin of the 2DEL at the celebrated LaAlO3/SrTiO3 interface and demonstrate an effective tool for tailoring the electronic structure at oxide interfaces.
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Affiliation(s)
- Danfeng Li
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Sébastien Lemal
- Theoretical Materials PhysicsQ‐MATCESAMUniversité de LiègeB‐4000LiègeBelgium
| | - Stefano Gariglio
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Zhenping Wu
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
- State Key Laboratory of Information Photonics and Optical Communications and School of ScienceBeijing University of Posts and TelecommunicationsBeijing100876China
| | - Alexandre Fête
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Margherita Boselli
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
| | - Philippe Ghosez
- Theoretical Materials PhysicsQ‐MATCESAMUniversité de LiègeB‐4000LiègeBelgium
| | - Jean‐Marc Triscone
- Department of Quantum Matter PhysicsUniversity of Geneva24 quai Ernest‐AnsermetCH‐1211Geneva 4Switzerland
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8
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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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9
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Electrons and Polarons at Oxide Interfaces Explored by Soft-X-Ray ARPES. SPECTROSCOPY OF COMPLEX OXIDE INTERFACES 2018. [DOI: 10.1007/978-3-319-74989-1_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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10
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Vaz DC, Lesne E, Sander A, Naganuma H, Jacquet E, Santamaria J, Barthélémy A, Bibes M. Tuning Up or Down the Critical Thickness in LaAlO 3 /SrTiO 3 through In Situ Deposition of Metal Overlayers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1700486. [PMID: 28505388 DOI: 10.1002/adma.201700486] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 03/28/2017] [Indexed: 06/07/2023]
Abstract
The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 and SrTiO3 has attracted much attention from the oxide electronics community. One of its hallmark features is the existence of a critical LaAlO3 thickness of 4 unit-cells (uc) for interfacial conductivity to emerge. In this paper, the chemical, electronic, and transport properties of LaAlO3 /SrTiO3 samples capped with different metals grown in a system combining pulsed laser deposition, sputtering, and in situ X-ray photoemission spectroscopy are investigated. The results show that for metals with low work function a q2DES forms at 1-2 uc of LaAlO3 and is accompanied by a partial oxidation of the metal, a phenomenon that affects the q2DES properties and triggers the formation of defects. In contrast, for noble metals, the critical thickness is increased above 4 uc. The results are discussed in terms of a hybrid mechanism that incorporates electrostatic and chemical effects.
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Affiliation(s)
- Diogo Castro Vaz
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - Edouard Lesne
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - Anke Sander
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - Hiroshi Naganuma
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Eric Jacquet
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - Jacobo Santamaria
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
- Instituto de Magnetismo Aplicado, Universidad Complutense de Madrid, 28040, Madrid, Spain
| | - Agnès Barthélémy
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - Manuel Bibes
- Unité Mixte de Physique UMR 137 CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
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11
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Wang Y, Tang W, Cheng J, Behtash M, Yang K. Creating Two-Dimensional Electron Gas in Polar/Polar Perovskite Oxide Heterostructures: First-Principles Characterization of LaAlO3/A(+)B(5+)O3. ACS APPLIED MATERIALS & INTERFACES 2016; 8:13659-13668. [PMID: 27160513 DOI: 10.1021/acsami.6b02399] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
By using first-principles electronic structure calculations, we explored the possibility of producing two-dimensional electron gas (2DEG) at the polar/polar (LaO)(+)/(BO2)(+) interface in the LaAlO3/A(+)B(5+)O3 (A = Na and K, B = Nb and Ta) heterostructures (HS). Unlike the prototype polar/nonpolar LaAlO3/SrTiO3 HS system where there exists a least film thickness of four LaAlO3 unit cells to have an insulator-to-metal transition, we found that the polar/polar LaAlO3/A(+)B(5+)O3 HS systems are intrinsically conducting at their interfaces without an insulator-to-metal transition. The interfacial charge carrier densities of these polar/polar HS systems are on the order of 10(14) cm(-2), much larger than that of the LaAlO3/SrTiO3 system. This is mainly attributed to two donor layers, i.e., (LaO)(+) and (BO2)(+) (B = Nb and Ta), in the polar/polar LaAlO3/A(+)B(5+)O3 systems, while only one (LaO)(+) donor layer in the polar/nonpolar LaAlO3/SrTiO3 system. In addition, it is expected that, due to less localized Nb 4d and Ta 5d orbitals with respect to Ti 3d orbitals, these LaAlO3/A(+)B(5+)O3 HS systems can exhibit potentially higher electron mobility because of their smaller electron effective mass than that in the LaAlO3/SrTiO3 system. Our results demonstrate that the electronic reconstruction at the polar/polar interface could be an alternative way to produce superior 2DEG in the perovskite-oxide-based HS systems.
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Affiliation(s)
- Yaqin Wang
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China , Chengdu, Sichuan 610054, P. R. China
- Department of NanoEngineering, University of California, San Diego , 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
| | - Wu Tang
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China , Chengdu, Sichuan 610054, P. R. China
| | - Jianli Cheng
- Department of NanoEngineering, University of California, San Diego , 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
| | - Maziar Behtash
- Department of NanoEngineering, University of California, San Diego , 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
| | - Kesong Yang
- Department of NanoEngineering, University of California, San Diego , 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
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12
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Cancellieri C, Mishchenko AS, Aschauer U, Filippetti A, Faber C, Barišić OS, Rogalev VA, Schmitt T, Nagaosa N, Strocov VN. Polaronic metal state at the LaAlO3/SrTiO3 interface. Nat Commun 2016; 7:10386. [PMID: 26813124 PMCID: PMC4737810 DOI: 10.1038/ncomms10386] [Citation(s) in RCA: 112] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 12/03/2015] [Indexed: 11/16/2022] Open
Abstract
Interplay of spin, charge, orbital and lattice degrees of freedom in oxide heterostructures results in a plethora of fascinating properties, which can be exploited in new generations of electronic devices with enhanced functionalities. The paradigm example is the interface between the two band insulators LaAlO3 and SrTiO3 that hosts a two-dimensional electron system. Apart from the mobile charge carriers, this system exhibits a range of intriguing properties such as field effect, superconductivity and ferromagnetism, whose fundamental origins are still debated. Here we use soft-X-ray angle-resolved photoelectron spectroscopy to penetrate through the LaAlO3 overlayer and access charge carriers at the buried interface. The experimental spectral function directly identifies the interface charge carriers as large polarons, emerging from coupling of charge and lattice degrees of freedom, and involving two phonons of different energy and thermal activity. This phenomenon fundamentally limits the carrier mobility and explains its puzzling drop at high temperatures.
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Affiliation(s)
- C. Cancellieri
- Swiss Light Source, Paul Scherrer Institute, Villigen CH-5232, Switzerland
- EMPA, Swiss Federal Laboratories for Materials Science & Technology, Ueberlandstrasse 129, Duebendorf 8600, Switzerland
| | - A. S. Mishchenko
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - U. Aschauer
- Materials Theory, ETH Zurich, Wolfgang-Pauli-Strasse 27, Zürich CH-8093, Switzerland
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3 3012 Bern, Switzerland
| | - A. Filippetti
- CNR-IOM, Istituto Officina dei Materiali, Cittadella Universitaria, Cagliari, Monserrato 09042-I, Italy
| | - C. Faber
- Materials Theory, ETH Zurich, Wolfgang-Pauli-Strasse 27, Zürich CH-8093, Switzerland
| | - O. S. Barišić
- Institute of Physics, Bijenička 46, 10000 Zagreb, Croatia
| | - V. A. Rogalev
- Swiss Light Source, Paul Scherrer Institute, Villigen CH-5232, Switzerland
| | - T. Schmitt
- Swiss Light Source, Paul Scherrer Institute, Villigen CH-5232, Switzerland
| | - N. Nagaosa
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - V. N. Strocov
- Swiss Light Source, Paul Scherrer Institute, Villigen CH-5232, Switzerland
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Electronic Structure of Oxide Interfaces: A Comparative Analysis of GdTiO3/SrTiO3 and LaAlO3/SrTiO3 Interfaces. Sci Rep 2015; 5:18647. [PMID: 26689360 PMCID: PMC4686895 DOI: 10.1038/srep18647] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 11/17/2015] [Indexed: 11/20/2022] Open
Abstract
Emergent phases in the two-dimensional electron gas (2DEG) formed at the interface between two insulating oxides have attracted great attention in the past decade. We present ab-initio electronic structure calculations for the interface between a Mott insulator GdTiO3 (GTO) and a band insulator SrTiO3 (STO) and compare our results with those for the widely studied LaAlO3/SrTiO3 (LAO/STO) interface between two band insulators. Our GTO/STO results are in excellent agreement with experiments, but qualitatively different from LAO/STO. We find an interface carrier density of 0.5 e−/Ti, independent of GTO thickness in both superlattice and thin film geometries, in contrast to LAO/STO. The superlattice geometry in LAO/STO offers qualitatively the same result as in GTO/STO. On the other hand, for a thin film geometry, the interface carrier density builds up only beyond a threshold thickness of LAO. The positive charge at the vacuum surface that compensates the 2DEG at the interface also exhibits distinct behaviors in the two systems. The compensating positive charge at the exposed surface of GTO charge disproportionates due to correlation effect making the surface insulating as opposed to that in LAO which remains metallic within band theory and presumably becomes insulating due to surface disorder or surface reconstruction.
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Gariglio S, Fête A, Triscone JM. Electron confinement at the LaAlO3/SrTiO3 interface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:283201. [PMID: 26102193 DOI: 10.1088/0953-8984/27/28/283201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Physical and structural phenomena originating from polar discontinuities have generated enormous activity. In the last ten years, the oxide interface between polar LaAlO(3) and non-polar SrTiO(3), both band insulators, has attracted particular interest, as it hosts an electron liquid with remarkable properties: it superconducts, has a sizeable spin-orbit interaction and its properties are tunable by an electric field. The profile of the carrier density at the interface and the exact band structure are properties strongly linked and still objects of debate. Here we review the experimental findings on the origin and the extension of the electron liquid and discuss the theoretical models developed to describe the charge profile and the band structure. We also introduce a model to account for the effect of interface disorder which could modify the charge distribution.
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Affiliation(s)
- S Gariglio
- DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève, Switzerland
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15
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Asmara TC, Santoso I, Rusydi A. Self-consistent iteration procedure in analyzing reflectivity and spectroscopic ellipsometry data of multilayered materials and their interfaces. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:123116. [PMID: 25554281 DOI: 10.1063/1.4897487] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
For multilayered materials, reflectivity depends on the complex dielectric function of all the constituent layers, and a detailed analysis is required to separate them. Furthermore, for some cases, new quantum states can occur at the interface which may change the optical properties of the material. In this paper, we discuss various aspects of such analysis, and present a self-consistent iteration procedure, a versatile method to extract and separate the complex dielectric function of each individual layer of a multilayered system. As a case study, we apply this method to LaAlO3/SrTiO3 heterostructure in which we are able to separate the effects of the interface from the LaAlO3 film and the SrTiO3 substrate. Our method can be applied to other complex multilayered systems with various numbers of layers.
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Affiliation(s)
- T C Asmara
- NUSNNI-NanoCore, Singapore Synchrotron Light Source, and Department of Physics, National University of Singapore, Singapore 117576
| | - I Santoso
- NUSNNI-NanoCore, Singapore Synchrotron Light Source, and Department of Physics, National University of Singapore, Singapore 117576
| | - A Rusydi
- NUSNNI-NanoCore, Singapore Synchrotron Light Source, and Department of Physics, National University of Singapore, Singapore 117576
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16
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Asmara T, Annadi A, Santoso I, Gogoi P, Kotlov A, Omer H, Motapothula M, Breese M, Rübhausen M, Venkatesan T, Ariando, Rusydi A. Mechanisms of charge transfer and redistribution in LaAlO3/SrTiO3 revealed by high-energy optical conductivity. Nat Commun 2014; 5:3663. [DOI: 10.1038/ncomms4663] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 03/17/2014] [Indexed: 11/09/2022] Open
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17
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Rössle M, Kim KW, Dubroka A, Marsik P, Wang CN, Jany R, Richter C, Mannhart J, Schneider CW, Frano A, Wochner P, Lu Y, Keimer B, Shukla DK, Strempfer J, Bernhard C. Electric-field-induced polar order and localization of the confined electrons in LaAlO3/SrTiO3 heterostructures. PHYSICAL REVIEW LETTERS 2013; 110:136805. [PMID: 23581357 DOI: 10.1103/physrevlett.110.136805] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Indexed: 06/02/2023]
Abstract
With ellipsometry, x-ray diffraction, and resistance measurements we investigated the electric-field effect on the confined electrons at the LaAlO3/SrTiO3 interface. We obtained evidence that the localization of the electrons at negative gate voltage is induced, or at least enhanced, by a polar phase transition in SrTiO3 which strongly reduces the lattice polarizability and the subsequent screening. In particular, we show that the charge localization and the polar order of SrTiO3 both develop below ∼50 K and exhibit similar, unipolar hysteresis loops as a function of the gate voltage.
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Affiliation(s)
- M Rössle
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
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18
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Stanislavchuk TN, Kang TD, Rogers PD, Standard EC, Basistyy R, Kotelyanskii AM, Nita G, Zhou T, Carr GL, Kotelyanskii M, Sirenko AA. Synchrotron radiation-based far-infrared spectroscopic ellipsometer with full Mueller-matrix capability. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2013; 84:023901. [PMID: 23464221 DOI: 10.1063/1.4789495] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We developed far-IR spectroscopic ellipsometer at the U4IR beamline of the National Synchrotron Light Source in Brookhaven National Laboratory. This ellipsometer is able to measure both, rotating analyzer and full-Mueller matrix spectra using rotating retarders, and wire-grid linear polarizers. We utilize exceptional brightness of synchrotron radiation in the broad spectral range between about 20 and 4000 cm(-1). Fourier-transform infrared (FT-IR) spectrometer is used for multi-wavelength data acquisition. The sample stage has temperature variation between 4.2 and 450 K, wide range of θ-2θ angular rotation, χ tilt angle adjustment, and X-Y-Z translation. A LabVIEW-based software controls the motors, sample temperature, and FT-IR spectrometer and also allows to run fully automated experiments with pre-programmed measurement schedules. Data analysis is based on Berreman's 4 × 4 propagation matrix formalism to calculate the Mueller matrix parameters of anisotropic samples with magnetic permeability μ ≠ 1. A nonlinear regression of the rotating analyzer ellipsometry and∕or Mueller matrix (MM) spectra, which are usually acquired at variable angles of incidence and sample crystallographic orientations, allows extraction of dielectric constant and magnetic permeability tensors for bulk and thin-film samples. Applications of this ellipsometer setup for multiferroic and ferrimagnetic materials with μ ≠ 1 are illustrated with experimental results and simulations for TbMnO3 and Dy3Fe5O12 single crystals. We demonstrate how magnetic and electric dipoles, such as magnons and phonons, can be distinguished from a single MM measurement without adducing any modeling arguments. The parameters of magnetoelectric components of electromagnon excitations are determined using MM spectra of TbMnO3.
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Affiliation(s)
- T N Stanislavchuk
- Department of Physics, New Jersey Institute of Technology, Newark, New Jersey 07102, USA.
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19
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Biscaras J, Bergeal N, Hurand S, Grossetête C, Rastogi A, Budhani RC, LeBoeuf D, Proust C, Lesueur J. Two-dimensional superconducting phase in LaTiO3/SrTiO3 heterostructures induced by high-mobility carrier doping. PHYSICAL REVIEW LETTERS 2012; 108:247004. [PMID: 23004312 DOI: 10.1103/physrevlett.108.247004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Indexed: 06/01/2023]
Abstract
In this Letter, we show that a superconducting two-dimensional electron gas is formed at the LaTiO3/SrTiO3 interface whose transition temperature can be modulated by a back-gate voltage. The gas consists of two types of carriers: a majority of low-mobility carriers always present, and a few high-mobility ones that can be injected by electrostatic doping. The calculation of the electron spatial distribution in the confinement potential shows that the high-mobility electrons responsible for superconductivity set at the edge of the gas whose extension can be tuned by the field effect.
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Affiliation(s)
- J Biscaras
- LPEM-UMR8213/CNRS-ESPCI ParisTech-UPMC, 10 rue Vauquelin-75005 Paris, France
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20
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Yamamoto R, Bell C, Hikita Y, Hwang HY, Nakamura H, Kimura T, Wakabayashi Y. Structural comparison of n-type and p-type LaAlO3/SrTiO3 interfaces. PHYSICAL REVIEW LETTERS 2011; 107:036104. [PMID: 21838380 DOI: 10.1103/physrevlett.107.036104] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Indexed: 05/31/2023]
Abstract
Using a surface x-ray diffraction technique, we investigated the atomic structure of two types of interfaces between LaAlO3 and SrTiO3, that is, p-type (SrO/AlO2) and n-type (TiO2/LaO) interfaces. Our results demonstrate that the SrTiO3 in the sample with the n-type interface has a large polarized region, while that with the p-type interface has a limited polarized region. In addition, atomic intermixing was observed to extend deeper into the SrTiO3 substrate at the n-type interface compared to the p type. These differences result in distinct degrees of band bending, which likely contributes to the striking contrast in electrical conductivity between the two types of interfaces.
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Affiliation(s)
- Ryosuke Yamamoto
- Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan
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21
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Delugas P, Filippetti A, Fiorentini V, Bilc DI, Fontaine D, Ghosez P. Spontaneous 2-dimensional carrier confinement at the n-type SrTiO3/LaAlO3 interface. PHYSICAL REVIEW LETTERS 2011; 106:166807. [PMID: 21599400 DOI: 10.1103/physrevlett.106.166807] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Indexed: 05/30/2023]
Abstract
We describe the intrinsic mechanism of 2-dimensional electron confinement at the n-type SrTiO3/LaAlO3 interface as a function of the sheet carrier density n(s) via advanced first-principles calculations. Electrons localize spontaneously in Ti 3d(xy) levels within a thin (≲2 nm) interface-adjacent SrTiO3 region for n(s) lower than a threshold value n(c)∼10(14) cm(-2). For n(s)>n(c) a portion of charge flows into Ti 3d(xz)-d(yz) levels extending farther from the interface. This intrinsic confinement can be attributed to the interface-induced symmetry breaking and localized nature of Ti 3d t(2g) states. The sheet carrier density directly controls the binding energy and the spatial extension of the conductive region. A direct, quantitative relation of these quantities with n(s) is provided.
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Affiliation(s)
- Pietro Delugas
- CNR-IOM UOS Cagliari, Dipartimento di Fisica, Università di Cagliari, Monserrato (CA), Italy
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22
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Caviglia AD, Gariglio S, Cancellieri C, Sacépé B, Fête A, Reyren N, Gabay M, Morpurgo AF, Triscone JM. Two-dimensional quantum oscillations of the conductance at LaAlO3/SrTiO3 interfaces. PHYSICAL REVIEW LETTERS 2010; 105:236802. [PMID: 21231492 DOI: 10.1103/physrevlett.105.236802] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Indexed: 05/30/2023]
Abstract
We report on a study of magnetotransport in LaAlO3 /SrTiO3 interfaces characterized by mobilities of the order of several thousands cm2/V s. We observe Shubnikov-de Haas oscillations whose period depends only on the perpendicular component of the magnetic field. This observation directly indicates the formation of a two-dimensional electron gas originating from quantum confinement at the interface. From the temperature dependence of the oscillation amplitude we extract an effective carrier mass m* ≃ 1.45 m(e). An electric field applied in the back-gate geometry increases the mobility, the carrier density, and the oscillation frequency.
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Affiliation(s)
- A D Caviglia
- Département de Physique de la Matière Condensée, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
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23
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Ben Shalom M, Ron A, Palevski A, Dagan Y. Shubnikov-de Haas oscillations in SrTiO3/LaAlO3 interface. PHYSICAL REVIEW LETTERS 2010; 105:206401. [PMID: 21231249 DOI: 10.1103/physrevlett.105.206401] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2010] [Indexed: 05/30/2023]
Abstract
Quantum magnetic oscillations in SrTiO3/LaAlO3 interface are observed in the magnetoresistance. We study their frequency as a function of gate voltage and the evolution of their amplitude with temperature. The data are consistent with the Shubnikov-de Haas theory. The Hall resistivity ρ(xy) is nonlinear at low magnetic fields. ρ(xy) is fitted assuming multiple carrier contributions. We infer the density of the mobile charge carriers from the oscillations frequency and from Hall measurements. The comparison between these densities suggests multiple valley and spin degeneracy. The small amplitude of the oscillation is discussed in the framework of the multiple band scenario.
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Affiliation(s)
- M Ben Shalom
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel Aviv, 69978, Israel
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