1
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Ko W, Song SY, Yan J, Lado JL, Maksymovych P. Atomic-Scale Andreev Probe of Unconventional Superconductivity. NANO LETTERS 2023; 23:8310-8318. [PMID: 37640372 PMCID: PMC10510698 DOI: 10.1021/acs.nanolett.3c02658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 08/21/2023] [Indexed: 08/31/2023]
Abstract
Recent emergence of low-dimensional unconventional superconductors and their exotic interface properties calls for new approaches to probe the pairing symmetry, a fundamental and frequently elusive property of the superconducting condensate. Here, we introduce the unique capability of tunneling Andreev reflection (TAR) to probe unconventional pairing symmetry, utilizing the sensitivity of this technique to specific Andreev reflections. Specifically, suppression of the lowest-order Andreev reflection due to quantum interference but emergence of the higher-order Andreev processes provides direct evidence of the sign-changing order parameter in the paradigmatic FeSe superconductor. TAR spectroscopy also reveals two superconducting gaps, points to a possibility of a nodal gap structure, and directly confirms that superconductivity is locally suppressed along the nematic twin boundary, with preferential and near-complete suppression of the larger energy gap. Our findings therefore enable new, atomic-scale insight into microscopic, inhomogeneous, and interfacial properties of emerging quantum materials.
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Affiliation(s)
- Wonhee Ko
- Center
for Nanophase Materials Sciences, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department
of Physics and Astronomy, University of
Tennessee, Knoxville, Tennessee 37996, United States
| | - Sang Yong Song
- Center
for Nanophase Materials Sciences, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Jiaqiang Yan
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Jose L. Lado
- Department
of Applied Physics, Aalto University, 02150 Espoo, Finland
| | - Petro Maksymovych
- Center
for Nanophase Materials Sciences, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
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2
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Liu Y, Wei T, He G, Zhang Y, Wang Z, Wang J. Pair density wave state in a monolayer high-T c iron-based superconductor. Nature 2023; 618:934-939. [PMID: 37380693 DOI: 10.1038/s41586-023-06072-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 04/11/2023] [Indexed: 06/30/2023]
Abstract
The pair density wave (PDW) is an extraordinary superconducting state in which Cooper pairs carry non-zero momentum1,2. Evidence for the existence of intrinsic PDW order in high-temperature (high-Tc) cuprate superconductors3,4 and kagome superconductors5 has emerged recently. However, the PDW order in iron-based high-Tc superconductors has not been observed experimentally. Here, using scanning tunnelling microscopy and spectroscopy, we report the discovery of the PDW state in monolayer iron-based high-Tc Fe(Te,Se) films grown on SrTiO3(001) substrates. The PDW state with a period of λ ≈ 3.6aFe (aFe is the distance between neighbouring Fe atoms) is observed at the domain walls by the spatial electronic modulations of the local density of states, the superconducting gap and the π-phase shift boundaries of the PDW around the vortices of the intertwined charge density wave order. The discovery of the PDW state in the monolayer Fe(Te,Se) film provides a low-dimensional platform to study the interplay between the correlated electronic states and unconventional Cooper pairing in high-Tc superconductors.
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Affiliation(s)
- Yanzhao Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China
| | - Tianheng Wei
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China
| | - Guanyang He
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China
| | - Yi Zhang
- Department of Physics, Shanghai University, Shanghai, China
| | - Ziqiang Wang
- Department of Physics, Boston College, Chestnut Hill, MA, USA.
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China.
- Collaborative Innovation Center of Quantum Matter, Beijing, China.
- Hefei National Laboratory, Hefei, China.
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, China.
- Beijing Academy of Quantum Information Sciences, Beijing, China.
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3
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Song SY, Hua C, Bell L, Ko W, Fangohr H, Yan J, Halász GB, Dumitrescu EF, Lawrie BJ, Maksymovych P. Nematically Templated Vortex Lattices in Superconducting FeSe. NANO LETTERS 2023; 23:2822-2830. [PMID: 36940166 PMCID: PMC10103702 DOI: 10.1021/acs.nanolett.3c00125] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 02/16/2023] [Indexed: 06/18/2023]
Abstract
New pathways to controlling the morphology of superconducting vortex lattices─and their subsequent dynamics─are required to guide and scale vortex world-lines into a computing platform. We have found that the nematic twin boundaries align superconducting vortices in the adjacent terraces due to the incommensurate potential between vortices surrounding twin boundaries and those trapped within them. With the varying density and morphology of twin boundaries, the vortex lattice assumes several distinct structural phases, including square, regular, and irregular one-dimensional lattices. Through concomitant analysis of vortex lattice models, we have inferred the characteristic energetics of the twin boundary potential and furthermore predicted the existence of geometric size effects as a function of increasing confinement by the twin boundaries. These findings extend the ideas of directed control over vortex lattices to intrinsic topological defects and their self-organized networks, which have direct implications for the future design and control of strain-based topological quantum computing architectures.
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Affiliation(s)
- Sang Yong Song
- Center
for Nanophase Materials Sciences, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Chengyun Hua
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Luke Bell
- Department
of Physics, Yale University, New Haven, Connecticut 06520, United States
| | - Wonhee Ko
- Center
for Nanophase Materials Sciences, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department
of Physics and Astronomy, University of
Tennessee at Knoxville, Knoxville Tennessee 37996, United States
| | - Hans Fangohr
- Faculty
of Engineering and Physical Sciences, University
of Southampton, Southampton SO17 1BJ, U.K.
- Max Planck
Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Jiaqiang Yan
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Gábor B. Halász
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Eugene F. Dumitrescu
- Computational
Science and Engineering Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Benjamin J. Lawrie
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Petro Maksymovych
- Center
for Nanophase Materials Sciences, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
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4
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Grigoriev PD, Kochev VD, Orlov AP, Frolov AV, Sinchenko AA. Inhomogeneous Superconductivity Onset in FeSe Studied by Transport Properties. MATERIALS (BASEL, SWITZERLAND) 2023; 16:1840. [PMID: 36902961 PMCID: PMC10003944 DOI: 10.3390/ma16051840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 02/16/2023] [Accepted: 02/21/2023] [Indexed: 06/18/2023]
Abstract
Heterogeneous superconductivity onset is a common phenomenon in high-Tc superconductors of both the cuprate and iron-based families. It is manifested by a fairly wide transition from the metallic to zero-resistance states. Usually, in these strongly anisotropic materials, superconductivity (SC) first appears as isolated domains. This leads to anisotropic excess conductivity above Tc, and the transport measurements provide valuable information about the SC domain structure deep within the sample. In bulk samples, this anisotropic SC onset gives an approximate average shape of SC grains, while in thin samples, it also indicates the average size of SC grains. In this work, both interlayer and intralayer resistivity were measured as a function of temperature in FeSe samples of various thicknesses. To measure the interlayer resistivity, FeSe mesa structures oriented across the layers were fabricated using FIB. As the sample thickness decreases, a significant increase in superconducting transition temperature Tc is observed: Tc raises from 8 K in bulk material to 12 K in microbridges of thickness ∼40 nm. We applied analytical and numerical calculations to analyze these and earlier data and find the aspect ratio and size of the SC domains in FeSe consistent with our resistivity and diamagnetic response measurements. We propose a simple and fairly accurate method for estimating the aspect ratio of SC domains from Tc anisotropy in samples of various small thicknesses. The relationship between nematic and superconducting domains in FeSe is discussed. We also generalize the analytical formulas for conductivity in heterogeneous anisotropic superconductors to the case of elongated SC domains of two perpendicular orientations with equal volume fractions, corresponding to the nematic domain structure in various Fe-based superconductors.
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Affiliation(s)
- Pavel D. Grigoriev
- L.D. Landau Institute for Theoretical Physics, 142432 Chernogolovka, Russia
- Department of Theoretical Physics and Quantum Technologies, National University of Science and Technology ”MISiS”, 119049 Moscow, Russia
- P.N. Lebedev Physical Institute of RAS, 119991 Moscow, Russia
| | - Vladislav D. Kochev
- Department of Theoretical Physics and Quantum Technologies, National University of Science and Technology ”MISiS”, 119049 Moscow, Russia
| | - Andrey P. Orlov
- Kotel’nikov Institute of Radioengineering and Electronics of RAS, 125009 Moscow, Russia
- Institute of Nanotechnology of Microelectronics of RAS, 115487 Moscow, Russia
| | - Aleksei V. Frolov
- Kotel’nikov Institute of Radioengineering and Electronics of RAS, 125009 Moscow, Russia
| | - Alexander A. Sinchenko
- Kotel’nikov Institute of Radioengineering and Electronics of RAS, 125009 Moscow, Russia
- Laboratoire de Physique des Solides, Universite Paris-Saclay, 91405 Orsay, France
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5
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Kim JJ, Park MS, Lee KS, Joo SH, Yoo JH, Bhoi D, Min BH, Kim KH, Lee J. Observations of Nematicity, Dopants, and Zero-Bias Conductance Peaks for the Ca 0.9La 0.1FeAs 2 Superconductor. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:622. [PMID: 36838990 PMCID: PMC9962653 DOI: 10.3390/nano13040622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 01/30/2023] [Accepted: 01/31/2023] [Indexed: 06/18/2023]
Abstract
Ca1-xLaxFeAs2 (CLFA112) belongs to a new family of Fe-based superconductors (FeSCs) and has a unique crystal structure featuring an arsenic zigzag chain layer, which has been proposed to be a possible two-dimensional topological insulator. This suggests that CLFA112 is a potential topological superconductor-a platform to realize Majorana fermions. Up to now, even a clear superconducting (SC) gap in CLFA112 has never been observed, and the SC properties of CLFA112 remain largely elusive. In this letter, we report the results of an atomic-scale investigation of the electronic structure of CLFA112 crystals using low-temperature scanning tunneling microscopy (STM). We revealed four different types of surfaces exhibiting distinct electronic properties, with all surfaces displaying dominating 2 × 1 surface reconstructions. On a Ca/La layer on top of an FeAs layer, a clear SC gap of ~12 mV was observed only at the crevices (vacancies) where the FeAs layer can be directly accessed. Remarkably, the FeAs termination layer displayed a dispersing nematic modulation both in real and q space. We also present peculiar zero-bias conductance peaks for the very As chain layer that is believed to exhibit a topological edge state as well as the influence of La dopants on the As chain layer.
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Affiliation(s)
- Jae-Joon Kim
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
- Samsung Electronics Semiconductor R&D Center, Hwaseong-si 18448, Gyeonggi-do, Republic of Korea
| | - Min Seok Park
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
| | - Kyoung Seok Lee
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
- Samsung Electronics Semiconductor R&D Center, Hwaseong-si 18448, Gyeonggi-do, Republic of Korea
| | - Sang Hyun Joo
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
- Samsung Electronics Semiconductor R&D Center, Hwaseong-si 18448, Gyeonggi-do, Republic of Korea
| | - Jung Hoon Yoo
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
| | - Dilip Bhoi
- Center for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
| | - Byeong Hun Min
- Center for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
| | - Kee Hoon Kim
- Center for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
| | - Jinho Lee
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
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6
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Yang Y, Wang Q, Duan S, Wo H, Huang C, Wang S, Gu L, Xiang D, Qian D, Zhao J, Zhang W. Anomalous Contribution to the Nematic Electronic States from the Structural Transition in FeSe Revealed by Time- and Angle-Resolved Photoemission Spectroscopy. PHYSICAL REVIEW LETTERS 2022; 128:246401. [PMID: 35776468 DOI: 10.1103/physrevlett.128.246401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 01/16/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
High-resolution time- and angle-resolved photoemission measurements were made on FeSe superconductors. With ultrafast photoexcitation, two critical excitation fluences that correspond to two ultrafast electronic phase transitions were found only in the d_{yz}-orbit-derived band near the Brillouin-zone center within our time and energy resolution. Upon comparison to the detailed temperature dependent measurements, we conclude that there are two equilibrium electronic phase transitions (at approximately 90 and 120 K) above the superconducting transition temperature, and an anomalous contribution on the scale of 10 meV to the nematic states from the structural transition is experimentally determined. Our observations strongly suggest that the electronic phase transition at 120 K must be taken into account in the energy band development of FeSe, and, furthermore, the contribution of the structural transition plays an important role in the nematic phase of iron-based high-temperature superconductors.
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Affiliation(s)
- Yuanyuan Yang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Qisi Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Shaofeng Duan
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Hongliang Wo
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Chaozhi Huang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Shichong Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Lingxiao Gu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Dao Xiang
- Key Laboratory for Laser Plasmas (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Dong Qian
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jun Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute of Nanoelectronics and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Wentao Zhang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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7
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Zhao LL, Li YZ, Zhao XM, Dai TA, Li YR, Meng LJ. Dirac-cone-like electronic states on nematic antiferromagnetic FeSe and FeTe. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:325801. [PMID: 35605598 DOI: 10.1088/1361-648x/ac7277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
We investigate the Dirac-cone-like (DCL) topological electronic properties of nematic-like antiferromagnetic (AFM) states of monolayer FeSe and FeTe designed artificially through first-principles calculations and Wannier-function-based tight-binding (WFTB) method. Our calculations reveal most of them have a pair of DCL bands on the Γ-Xline in the Brillouin zone (BZ) near the Fermi level and open a gap of about 20 meV in the absence and presence of spin-orbit coupling (SOC), respectively, similar to the lowest-energy pair-checkerboard AFM FeSe. We further confirm that they are weak topological insulators based on nonzeroZ2and fragile surface states, which are calculated by the WFTB method. For FeSe and FeTe in pair-checkerboard AFM states, we find that the in-plane compression strain in a certain range can give rise to another pair of DCL bands located on the Γ-X' line in the BZ. In addition, the magnetic moments, energies, and Fe-Se/Te distances for various nematic-like AFM configurations are presented. These calculations the combining effect of magnetism and topology in a single material and the understanding of the superconducting phenomena in iron-based FeSe and FeTe.
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Affiliation(s)
- L L Zhao
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
| | - Y Z Li
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
| | - X M Zhao
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
| | - T A Dai
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
| | - Y R Li
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
| | - L J Meng
- School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, Hunan, People's Republic of China
- Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Hunan, People's Republic of China
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8
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Iron pnictides and chalcogenides: a new paradigm for superconductivity. Nature 2022; 601:35-44. [PMID: 34987212 DOI: 10.1038/s41586-021-04073-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 09/29/2021] [Indexed: 11/09/2022]
Abstract
Superconductivity is a remarkably widespread phenomenon that is observed in most metals cooled to very low temperatures. The ubiquity of such conventional superconductors, and the wide range of associated critical temperatures, is readily understood in terms of the well-known Bardeen-Cooper-Schrieffer theory. Occasionally, however, unconventional superconductors are found, such as the iron-based materials, which extend and defy this understanding in unexpected ways. In the case of the iron-based superconductors, this includes the different ways in which the presence of multiple atomic orbitals can manifest in unconventional superconductivity, giving rise to a rich landscape of gap structures that share the same dominant pairing mechanism. In addition, these materials have also led to insights into the unusual metallic state governed by the Hund's interaction, the control and mechanisms of electronic nematicity, the impact of magnetic fluctuations and quantum criticality, and the importance of topology in correlated states. Over the fourteen years since their discovery, iron-based superconductors have proven to be a testing ground for the development of novel experimental tools and theoretical approaches, both of which have extensively influenced the wider field of quantum materials.
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9
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Cao Y, Rodan-Legrain D, Park JM, Yuan NFQ, Watanabe K, Taniguchi T, Fernandes RM, Fu L, Jarillo-Herrero P. Nematicity and competing orders in superconducting magic-angle graphene. Science 2021; 372:264-271. [DOI: 10.1126/science.abc2836] [Citation(s) in RCA: 103] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 03/12/2021] [Indexed: 01/18/2023]
Affiliation(s)
- Yuan Cao
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Daniel Rodan-Legrain
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jeong Min Park
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Noah F. Q. Yuan
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Rafael M. Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Pablo Jarillo-Herrero
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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10
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Bu K, Zhang W, Fei Y, Zheng Y, Ai F, Wu Z, Wang Q, Wo H, Zhao J, Yin Y. Observation of an electronic order along [110] direction in FeSe. Nat Commun 2021; 12:1385. [PMID: 33654059 PMCID: PMC7925548 DOI: 10.1038/s41467-021-21318-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 01/17/2021] [Indexed: 11/30/2022] Open
Abstract
Multiple ordered states have been observed in unconventional superconductors. Here, we apply scanning tunneling microscopy to probe the intrinsic ordered states in FeSe, the structurally simplest iron-based superconductor. Besides the well-known nematic order along [100] direction, we observe a checkerboard charge order in the iron lattice, which we name a [110] electronic order in FeSe. The [110] electronic order is robust at 77 K, accompanied with the rather weak [100] nematic order. At 4.5 K, The [100] nematic order is enhanced, while the [110] electronic order forms domains with reduced correlation length. In addition, the collective [110] order is gaped around [−40, 40] meV at 4.5 K. The observation of this exotic electronic order may shed new light on the origin of the ordered states in FeSe. Understanding the relation of different electronic orders in high temperature superconductors is of fundamental interest. Here, the authors observe a checkerboard charge order along [110] direction of FeSe.
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Affiliation(s)
- Kunliang Bu
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Wenhao Zhang
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Ying Fei
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Yuan Zheng
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Fangzhou Ai
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Zongxiu Wu
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
| | - Qisi Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China
| | - Hongliang Wo
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China
| | - Jun Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China.,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
| | - Yi Yin
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China. .,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China.
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11
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Ren Z, Li H, Zhao H, Sharma S, Wang Z, Zeljkovic I. Nanoscale decoupling of electronic nematicity and structural anisotropy in FeSe thin films. Nat Commun 2021; 12:10. [PMID: 33397896 PMCID: PMC7782804 DOI: 10.1038/s41467-020-20150-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 11/18/2020] [Indexed: 11/09/2022] Open
Abstract
In a material prone to a nematic instability, anisotropic strain in principle provides a preferred symmetry-breaking direction for the electronic nematic state to follow. This is consistent with experimental observations, where electronic nematicity and structural anisotropy typically appear hand-in-hand. In this work, we discover that electronic nematicity can be locally decoupled from the underlying structural anisotropy in strain-engineered iron-selenide (FeSe) thin films. We use heteroepitaxial molecular beam epitaxy to grow FeSe with a nanoscale network of modulations that give rise to spatially varying strain. We map local anisotropic strain by analyzing scanning tunneling microscopy topographs, and visualize electronic nematic domains from concomitant spectroscopic maps. While the domains form so that the energy of nemato-elastic coupling is minimized, we observe distinct regions where electronic nematic ordering fails to flip direction, even though the underlying structural anisotropy is locally reversed. The findings point towards a nanometer-scale stiffness of the nematic order parameter.
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Affiliation(s)
- Zheng Ren
- Department of Physics, Boston College, 140 Commonwealth Ave, Chestnut Hill, MA, 02467, USA
| | - Hong Li
- Department of Physics, Boston College, 140 Commonwealth Ave, Chestnut Hill, MA, 02467, USA
| | - He Zhao
- Department of Physics, Boston College, 140 Commonwealth Ave, Chestnut Hill, MA, 02467, USA
| | - Shrinkhala Sharma
- Department of Physics, Boston College, 140 Commonwealth Ave, Chestnut Hill, MA, 02467, USA
| | - Ziqiang Wang
- Department of Physics, Boston College, 140 Commonwealth Ave, Chestnut Hill, MA, 02467, USA
| | - Ilija Zeljkovic
- Department of Physics, Boston College, 140 Commonwealth Ave, Chestnut Hill, MA, 02467, USA.
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12
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Stolyarov VS, Pervakov KS, Astrakhantseva AS, Golovchanskiy IA, Vyalikh DV, Kim TK, Eremeev SV, Vlasenko VA, Pudalov VM, Golubov AA, Chulkov EV, Roditchev D. Electronic Structures and Surface Reconstructions in Magnetic Superconductor RbEuFe 4As 4. J Phys Chem Lett 2020; 11:9393-9399. [PMID: 33095988 DOI: 10.1021/acs.jpclett.0c02711] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In pnictide RbEuFe4As4, superconductivity sets in at 36 K and coexists, below 15-19 K, with the long-range magnetic ordering of Eu 4f spins. Here we report scanning tunneling experiments performed on cold-cleaved single crystals of the compound. The data revealed the coexistence of large Rb-terminated and small Eu-terminated terraces, both manifesting 1 × 2 and 2×2 reconstructions. On 2×2 surfaces, a hidden electronic order with a period ∼5 nm was discovered. A superconducting gap of ∼7 meV was seen to be strongly filled with quasiparticle states. The tunneling spectra compared with density functional theory calculations confirmed that flat electronic bands due to Eu 4f orbitals are situated ∼1.8 eV below the Fermi level and thus do not contribute directly to Cooper pair formation.
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Affiliation(s)
- Vasily S Stolyarov
- Moscow Institute of Physics and Technology, Dolgoprudny, 141700 Moscow, Russia
- Dukhov Research Institute of Automatics (VNIIA), 127055 Moscow, Russia
| | - Kirill S Pervakov
- Ginzburg Center for High Temperature Superconductivity and Quantum Materials, Lebedev Physical Institute, 119991 Moscow, Russia
| | | | - Igor A Golovchanskiy
- Moscow Institute of Physics and Technology, Dolgoprudny, 141700 Moscow, Russia
- National University of Science and Technology MISIS, 119049 Moscow, Russia
| | - Denis V Vyalikh
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Timur K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - Sergey V Eremeev
- Institute of Strength Physics and Materials Science, Russian Academy of Sciences, 634055 Tomsk, Russia
| | - Vladimir A Vlasenko
- Ginzburg Center for High Temperature Superconductivity and Quantum Materials, Lebedev Physical Institute, 119991 Moscow, Russia
| | - Vladimir M Pudalov
- Ginzburg Center for High Temperature Superconductivity and Quantum Materials, Lebedev Physical Institute, 119991 Moscow, Russia
- National Research University Higher School of Economics, 101000 Moscow, Russia
| | - Alexander A Golubov
- Moscow Institute of Physics and Technology, Dolgoprudny, 141700 Moscow, Russia
- Faculty of Science and Technology and MESA+, Institute of Nanotechnology, 7500 AE Enschede, The Netherlands
| | - Eugene V Chulkov
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Basque Country, Spain
- National Research University Higher School of Economics, 101000 Moscow, Russia
| | - Dimitri Roditchev
- Laboratoire de Physique et d'Etude des Materiaux, LPEM, UMR-8213, ESPCI-Paris, PSL, CNRS, Sorbonne University, 75005 Paris, France
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13
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Abstract
We have measured the angle-resolved transverse resistivity (ARTR), a sensitive indicator of electronic anisotropy, in high-quality thin films of the unconventional superconductor Sr2RuO4 grown on various substrates. The ARTR signal, heralding the electronic nematicity or a large nematic susceptibility, is present and substantial already at room temperature and grows by an order of magnitude upon cooling down to 4 K. In Sr2RuO4 films deposited on tetragonal substrates the highest-conductivity direction does not coincide with any crystallographic axis. In films deposited on orthorhombic substrates it tends to align with the shorter axis; however, the magnitude of the anisotropy stays the same despite the large lattice distortion. These are strong indications of actual or incipient electronic nematicity in Sr2RuO4.
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14
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Wang X, Yuan Y, Xue QK, Li W. Charge ordering in high-temperature superconductors visualized by scanning tunneling microscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:013002. [PMID: 31487703 DOI: 10.1088/1361-648x/ab41c5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Since the discovery of stripe order in La1.6-x Nd0.4Sr x CuO4 superconductors in 1995, charge ordering in cuprate superconductors has been intensively studied by various experimental techniques. Among these studies, scanning tunneling microscope (STM) plays an irreplaceable role in determining the real space structures of charge ordering. STM imaging of different families of cuprates over a wide range of doping levels reveal similar checkerboard-like patterns, indicating that such a charge ordered state is likely a ubiquitous and intrinsic characteristic of cuprate superconductors, which may shed light on understanding the mechanism of high-temperature superconductivity. In another class of high-temperature superconductors, iron-based superconductors, STM studies reveal several charge ordered states as well, but their real-space patterns and the interplay with superconductivity are markedly different among different materials. In this paper, we present a brief review on STM studies of charge ordering in these two classes of high-temperature superconductors. Possible origins of charge ordering and its interplay with superconductivity will be discussed.
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Affiliation(s)
- Xintong Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China. Collaborative Innovation Center of Quantum Matter, Beijing 100084, People's Republic of China
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15
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Liu X, Tao R, Ren M, Chen W, Yao Q, Wolf T, Yan Y, Zhang T, Feng D. Evidence of nematic order and nodal superconducting gap along [110] direction in RbFe 2As 2. Nat Commun 2019; 10:1039. [PMID: 30833562 PMCID: PMC6399313 DOI: 10.1038/s41467-019-08962-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 02/12/2019] [Indexed: 11/09/2022] Open
Abstract
Unconventional superconductivity often intertwines with various forms of order, such as the nematic order which breaks the rotational symmetry of the lattice. Here we report a scanning tunneling microscopy study on RbFe2As2, a heavily hole-doped Fe-based superconductor (FeSC). We observe significant symmetry breaking in its electronic structure and magnetic vortex which differentiates the (π, π) and (π, -π) directions of the unfolded Brillouin zone. It is thus a novel nematic state, distinct from the nematicity of undoped/lightly-doped FeSCs which breaks the (π, 0)/(0, π) equivalence. Moreover, we observe a clear V-shaped superconducting gap. The gap is suppressed on surface Rb vacancies and step edges, and the suppression is particularly strong at the [110]-oriented edges. This is possibly due to a \documentclass[12pt]{minimal}
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\begin{document}$${{d}}_{{{x}}^2 - {{y}}^2}$$\end{document}dx2-y2 like pairing component with nodes along the [110] directions. Our results thus highlight the intimate connection between nematicity and superconducting pairing in iron-based superconductors. Exotic electronic order may emerge and intertwine with superconductivity in iron-based superconductors. Here, the authors observe asymmetric electronic and superconducting gap structure in heavily hole-doped RbFe2As2 along the (π, π) and (π, -π) directions in reciprocal space, suggesting a novel (π, π) nematic phase emerging.
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Affiliation(s)
- Xi Liu
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, 200433, Shanghai, China
| | - Ran Tao
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, 200433, Shanghai, China
| | - Mingqiang Ren
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, 200433, Shanghai, China
| | - Wei Chen
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, 200433, Shanghai, China
| | - Qi Yao
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, 200433, Shanghai, China
| | - Thomas Wolf
- Institute for Solid State Physics, Karlsruhe Institute of Technology, D-76021, Karlsruhe, Germany
| | - Yajun Yan
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, 200433, Shanghai, China
| | - Tong Zhang
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, 200433, Shanghai, China. .,Collaborative Innovation Center of Advanced Microstructures, 210093, Nanjing, China.
| | - Donglai Feng
- State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, 200433, Shanghai, China. .,Collaborative Innovation Center of Advanced Microstructures, 210093, Nanjing, China.
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16
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Joo SH, Kim JJ, Yoo JH, Park MS, Lee KS, Gu G, Lee J. Cooper Pair Density of Bi 2Sr 2CaCu 2O 8+ x in Atomic scale at 4.2 K. NANO LETTERS 2019; 19:1112-1117. [PMID: 30698977 DOI: 10.1021/acs.nanolett.8b04415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In pursuit of the elusive mechanism of high- T C superconductors (HTSC), spectroscopic imaging scanning tunneling microscopy (SI-STM) is an indispensable tool for surveying local properties of HTSC. Since a conventional STM utilizes metal tips, which allow the examination of only quasiparticles and not superconducting (SC) pairs, Josephson tunneling using STM has been demonstrated by many authors in the past. An atomically resolved scanning Josephson tunneling microscopy (SJTM), however, was realized only recently on Bi2Sr2CaCu2O8+ x (Bi-2212) below 50 mK and on the Pb(110) surface at 20 mK. Here we report the atomically resolved SJTM on Bi2Sr2CaCu2O8+ x at 4.2 K using Bi-2212 tips created in situ. The I- V characteristics show clear zero bias conductance peaks following Ambegaokar-Baratoff (AB) theory. A gap map was produced for the first time using an atomically resolved Josephson critical current map I C( r) and AB theory. Surprisingly, we found that this new gap map is anticorrelated to the gap map produced by a conventional method relying on the coherence peaks. Quasiparticle resonance due to a single isolated zinc atom impurity was also observed by SJTM, indicating that atomically resolved SJTM was achieved at 4.2 K. Our result provides a starting point for realizing SJTM at even higher temperatures, rendering possible investigation of the existence of SC pairs in HTSC above the T C.
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Affiliation(s)
- S H Joo
- Department of Physics and Astronomy , Seoul National University (SNU) , Seoul 08826 , Republic of Korea
- Center for Correlated Electron Systems , Institute for Basic Science (IBS) , Seoul 08826 , Republic of Korea
| | - J-J Kim
- Department of Physics and Astronomy , Seoul National University (SNU) , Seoul 08826 , Republic of Korea
- Center for Correlated Electron Systems , Institute for Basic Science (IBS) , Seoul 08826 , Republic of Korea
| | - J H Yoo
- Department of Physics and Astronomy , Seoul National University (SNU) , Seoul 08826 , Republic of Korea
- Center for Correlated Electron Systems , Institute for Basic Science (IBS) , Seoul 08826 , Republic of Korea
| | - M S Park
- Department of Physics and Astronomy , Seoul National University (SNU) , Seoul 08826 , Republic of Korea
- Center for Correlated Electron Systems , Institute for Basic Science (IBS) , Seoul 08826 , Republic of Korea
| | - K S Lee
- Department of Physics and Astronomy , Seoul National University (SNU) , Seoul 08826 , Republic of Korea
- Center for Correlated Electron Systems , Institute for Basic Science (IBS) , Seoul 08826 , Republic of Korea
| | - G Gu
- CMPMS Department , Brookhaven National Laboratory , Upton , New York 11973 , United States
| | - Jinho Lee
- Department of Physics and Astronomy , Seoul National University (SNU) , Seoul 08826 , Republic of Korea
- Center for Correlated Electron Systems , Institute for Basic Science (IBS) , Seoul 08826 , Republic of Korea
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17
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Lv Y, Dong Y, Lu D, Tian W, Xu Z, Chen W, Zhou X, Yuan J, Jin K, Bao S, Li S, Wen J, Chibotaru LF, Schwarz T, Kleiner R, Koelle D, Li J, Wang H, Wu P. Anomalous transverse resistance in 122-type iron-based superconductors. Sci Rep 2019; 9:664. [PMID: 30679657 PMCID: PMC6345833 DOI: 10.1038/s41598-018-37152-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 11/25/2018] [Indexed: 11/13/2022] Open
Abstract
The study of transverse resistance of superconductors is essential to understand the transition to superconductivity. Here, we investigated the in-plane transverse resistance of Ba0.5K0.5Fe2As2 superconductors, based on ultra-thin micro-bridges fabricated from optimally doped single crystals. An anomalous transverse resistance was found at temperatures around the superconducting transition, although magnetic order or structure distortion are absent in the optimal doping case. With the substitution of magnetic and nonmagnetic impurities into the superconducting layer, the anomalous transverse resistance phenomenon is dramatically enhanced. We find that anisotropic scattering or the superconducting electronic nematic state related with the superconducting transition may contribute to this phenomenon.
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Affiliation(s)
- Yangyang Lv
- Research Institute of Superconductor Electronics, Nanjing University, Nanjing, 210023, China
| | - Yu Dong
- Research Institute of Superconductor Electronics, Nanjing University, Nanjing, 210023, China
| | - Dachuan Lu
- Research Institute of Superconductor Electronics, Nanjing University, Nanjing, 210023, China
| | - Wanghao Tian
- Research Institute of Superconductor Electronics, Nanjing University, Nanjing, 210023, China
| | - Zuyu Xu
- Research Institute of Superconductor Electronics, Nanjing University, Nanjing, 210023, China
| | - Wei Chen
- Research Institute of Superconductor Electronics, Nanjing University, Nanjing, 210023, China
| | - Xianjing Zhou
- Research Institute of Superconductor Electronics, Nanjing University, Nanjing, 210023, China
| | - Jie Yuan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,Key Laboratory for Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Kui Jin
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,Key Laboratory for Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Song Bao
- School of Physics, Nanjing University, Nanjing, 210023, China.,National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing, 210093, China
| | - Shichao Li
- School of Physics, Nanjing University, Nanjing, 210023, China.,National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing, 210093, China
| | - Jinsheng Wen
- School of Physics, Nanjing University, Nanjing, 210023, China.,National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing, 210093, China
| | - Liviu F Chibotaru
- Theory of Nanomaterials Group, KU Leuven, Celestijnenlaan 200F, Leuven, B-3001, Belgium
| | - Tobias Schwarz
- Physikalisches Institut-Experimentalphysik II and Center for Collective Quantum Phenomena in LISA, Universität Tübingen, Auf der Morgenstelle 14, Tübingen, D-72076, Germany
| | - Reinhold Kleiner
- Physikalisches Institut-Experimentalphysik II and Center for Collective Quantum Phenomena in LISA, Universität Tübingen, Auf der Morgenstelle 14, Tübingen, D-72076, Germany
| | - Dieter Koelle
- Physikalisches Institut-Experimentalphysik II and Center for Collective Quantum Phenomena in LISA, Universität Tübingen, Auf der Morgenstelle 14, Tübingen, D-72076, Germany
| | - Jun Li
- Research Institute of Superconductor Electronics, Nanjing University, Nanjing, 210023, China.
| | - Huabing Wang
- Research Institute of Superconductor Electronics, Nanjing University, Nanjing, 210023, China
| | - Peiheng Wu
- Research Institute of Superconductor Electronics, Nanjing University, Nanjing, 210023, China.,Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, 230026, Anhui, China
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18
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Yuan Y, Li W, Liu B, Deng P, Xu Z, Chen X, Song C, Wang L, He K, Xu G, Ma X, Xue QK. Edge States at Nematic Domain Walls in FeSe Films. NANO LETTERS 2018; 18:7176-7180. [PMID: 30350654 DOI: 10.1021/acs.nanolett.8b03282] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Quantum spin Hall (QSH) effect is an intriguing phenomenon arising from the helical edge states in two-dimensional topological insulators. We use molecular beam epitaxy (MBE) to prepare FeSe films with atomically sharp nematic domain boundaries, where tensile strains, nematicity suppression, and topological band inversion are simultaneously achieved. Using scanning tunneling microscopy (STM), we observe edge states at the Fermi level that spatially distribute as two distinct strips in the vicinity of the domain boundaries. At the end point of the boundaries, a bound state at the Fermi level is further observed. The topological origin of the edge states is supported by density functional theory calculations. Our findings not only demonstrate a candidate for QSH states but also provide a new pathway to realize topological superconductivity in a single-component film.
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Affiliation(s)
- Yonghao Yuan
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
| | - Wei Li
- 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
- Beijing Academy of Quantum Information Sciences , Beijing 100193 , China
| | - Bin Liu
- Wuhan National High Magnetic Field Center & School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Peng Deng
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
| | - Zhilin Xu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
| | - Xi Chen
- 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
| | - Canli 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
| | - 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
| | - 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
- Beijing Academy of Quantum Information Sciences , Beijing 100193 , China
| | - Gang Xu
- Wuhan National High Magnetic Field Center & School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Xucun 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
| | - 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
- Beijing Academy of Quantum Information Sciences , Beijing 100193 , China
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19
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Yin JX, Zhang SS, Li H, Jiang K, Chang G, Zhang B, Lian B, Xiang C, Belopolski I, Zheng H, Cochran TA, Xu SY, Bian G, Liu K, Chang TR, Lin H, Lu ZY, Wang Z, Jia S, Wang W, Hasan MZ. Giant and anisotropic many-body spin–orbit tunability in a strongly correlated kagome magnet. Nature 2018; 562:91-95. [DOI: 10.1038/s41586-018-0502-7] [Citation(s) in RCA: 176] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 07/04/2018] [Indexed: 11/09/2022]
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20
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Blomberg EC, Tanatar MA, Thaler A, Bud'ko SL, Canfield PC, Prozorov R. Multi-band effects in in-plane resistivity anisotropy of strain-detwinned disordered Ba(Fe 1-xRu x) 2As 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:315601. [PMID: 29992907 DOI: 10.1088/1361-648x/aacf2e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In-plane resistivity anisotropy was measured in strain-detwinned as-grown and partially annealed samples of isovalently-substituted [Formula: see text] ([Formula: see text]) and the results were contrasted with previous reports on anneal samples with low residual resistivity. In samples with high residual resistivity, detwinned with application of strain, the difference of the two components of in-plane resistivity in the orthorhombic phase, [Formula: see text], was found to obey Matthiessen rule irrespective of sample composition, which is in stark contrast with observations on annealed samples. Our findings are consistent with two-band transport model in which contribution from high mobility carriers of small pockets of the Fermi surface has negligible anisotropy of residual resistivity and is eliminated by disorder. Our finding suggests that magnetic/nematic order has dramatically different effect on different parts of the Fermi surface. It predominantly affects inelastic scattering for small pocket high mobility carriers and elastic impurity scattering for larger sheets of the Fermi surface.
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Affiliation(s)
- E C Blomberg
- Ames Laboratory USDOE and Department of Physics and Astronomy, Iowa State University, Ames, IA, United States of America
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21
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Kim S, Yi S, Oh M, Jang BG, Nam W, Yoo YC, Lee M, Jeon H, Zoh I, Lee H, Zhang C, Kim KH, Seo J, Shim JH, Chae J, Kuk Y. Surface reconstruction and charge modulation in BaFe 2As 2 superconducting film. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:315001. [PMID: 29916822 DOI: 10.1088/1361-648x/aacd85] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Whether or not epitaxially grown superconducting films have the same bulk-like superconducting properties is an important concern. We report the structure and the electronic properties of epitaxially grown Ba(Fe1-x Co x )2As2 films using scanning tunneling microscopy and scanning tunneling spectroscopy (STS). This film showed a different surface structure, [Formula: see text]R45° reconstruction, from those of as-cleaved surfaces from bulk crystals. The electronic structure of the grown film is different from that in bulk, and it is notable that the film exhibits the same superconducting transport properties. We found that the superconducting gap at the surface is screened at the Ba layer surface in STS measurements, and the charge density wave was observed at the surface in sample in the superconducting state.
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Affiliation(s)
- S Kim
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
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22
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Yim CM, Trainer C, Aluru R, Chi S, Hardy WN, Liang R, Bonn D, Wahl P. Discovery of a strain-stabilised smectic electronic order in LiFeAs. Nat Commun 2018; 9:2602. [PMID: 29973598 PMCID: PMC6031620 DOI: 10.1038/s41467-018-04909-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 06/04/2018] [Indexed: 11/09/2022] Open
Abstract
In many high temperature superconductors, small orthorhombic distortions of the lattice structure result in surprisingly large symmetry breaking of the electronic states and macroscopic properties, an effect often referred to as nematicity. To directly study the impact of symmetry-breaking lattice distortions on the electronic states, using low-temperature scanning tunnelling microscopy we image at the atomic scale the influence of strain-tuned lattice distortions on the correlated electronic states in the iron-based superconductor LiFeAs, a material which in its ground state is tetragonal with four-fold (C4) symmetry. Our experiments uncover a new strain-stabilised modulated phase which exhibits a smectic order in LiFeAs, an electronic state which not only breaks rotational symmetry but also reduces translational symmetry. We follow the evolution of the superconducting gap from the unstrained material with C4 symmetry through the new smectic phase with two-fold (C2) symmetry and charge-density wave order to a state where superconductivity is completely suppressed.
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Affiliation(s)
- Chi Ming Yim
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
| | - Christopher Trainer
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
| | - Ramakrishna Aluru
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK
| | - Shun Chi
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Walter N Hardy
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Ruixing Liang
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Doug Bonn
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Peter Wahl
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK.
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23
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Böhmer AE, Kreisel A. Nematicity, magnetism and superconductivity in FeSe. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:023001. [PMID: 29240560 DOI: 10.1088/1361-648x/aa9caa] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c, ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.
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Affiliation(s)
- Anna E Böhmer
- Ames Laboratory, US DOE, Ames, IA 50011, United States of America
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24
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Abstract
The paradigmatic example of a continuous quantum phase transition is the transverse field Ising ferromagnet. In contrast to classical critical systems, whose properties depend only on symmetry and the dimension of space, the nature of a quantum phase transition also depends on the dynamics. In the transverse field Ising model, the order parameter is not conserved, and increasing the transverse field enhances quantum fluctuations until they become strong enough to restore the symmetry of the ground state. Ising pseudospins can represent the order parameter of any system with a twofold degenerate broken-symmetry phase, including electronic nematic order associated with spontaneous point-group symmetry breaking. Here, we show for the representative example of orbital-nematic ordering of a non-Kramers doublet that an orthogonal strain or a perpendicular magnetic field plays the role of the transverse field, thereby providing a practical route for tuning appropriate materials to a quantum critical point. While the transverse fields are conjugate to seemingly unrelated order parameters, their nontrivial commutation relations with the nematic order parameter, which can be represented by a Berry-phase term in an effective field theory, intrinsically intertwine the different order parameters.
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Nematic superconducting state in iron pnictide superconductors. Nat Commun 2017; 8:1880. [PMID: 29192211 PMCID: PMC5709366 DOI: 10.1038/s41467-017-02016-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Accepted: 10/31/2017] [Indexed: 12/01/2022] Open
Abstract
Nematic order often breaks the tetragonal symmetry of iron-based superconductors. It arises from regular structural transition or electronic instability in the normal phase. Here, we report the observation of a nematic superconducting state, by measuring the angular dependence of the in-plane and out-of-plane magnetoresistivity of Ba0.5K0.5Fe2As2 single crystals. We find large twofold oscillations in the vicinity of the superconducting transition, when the direction of applied magnetic field is rotated within the basal plane. To avoid the influences from sample geometry or current flow direction, the sample was designed as Corbino-shape for in-plane and mesa-shape for out-of-plane measurements. Theoretical analysis shows that the nematic superconductivity arises from the weak mixture of the quasi-degenerate s-wave and d-wave components of the superconducting condensate, most probably induced by a weak anisotropy of stresses inherent to single crystals. Nematic electronic order is rare and its onset often indicates a phase transition. Here, Li et al. report a nematic superconducting state in Ba0.5K0.5Fe2As2 by measuring the angular dependence of the in-plane and out-of-plane magnetoresistivity.
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26
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Singh DK. Spin-wave excitations in the spin-density wave state of doped iron pnictides. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:415601. [PMID: 28869752 DOI: 10.1088/1361-648x/aa7e13] [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
We investigate spin-wave excitations in the spin-density wave state of doped iron pnictides within a five-orbital model. We find that the excitations along ([Formula: see text]) → ([Formula: see text]) are very sensitive to dopings whereas they do not exhibit a similar sensitivity along ([Formula: see text]) → ([Formula: see text]). Secondly, the ellipticity of the elliptical ring-like excitations around ([Formula: see text]) is also very much dependent on doping. Thirdly, the spin-wave spectral weight shifts towards the low-energy region as it moves away from zero doping. We find several features to be in qualitative agreement with the inelastic neutron-scattering measurements for the doped pnictides.
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Affiliation(s)
- Dheeraj Kumar Singh
- Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211019, India. Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085, India
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27
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Harter JW, Zhao ZY, Yan JQ, Mandrus DG, Hsieh D. A parity-breaking electronic nematic phase transition in the spin-orbit coupled metal Cd
2
Re
2
O
7. Science 2017; 356:295-299. [DOI: 10.1126/science.aad1188] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 03/20/2017] [Indexed: 11/02/2022]
Affiliation(s)
- J. W. Harter
- Department of Physics, California Institute of Technology, Pasadena, CA 91125, USA
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA 91125, USA
| | - Z. Y. Zhao
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA
| | - J.-Q. Yan
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA
| | - D. G. Mandrus
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA
| | - D. Hsieh
- Department of Physics, California Institute of Technology, Pasadena, CA 91125, USA
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, CA 91125, USA
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28
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Fernandes RM, Chubukov AV. Low-energy microscopic models for iron-based superconductors: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:014503. [PMID: 27876709 DOI: 10.1088/1361-6633/80/1/014503] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The development of sensible microscopic models is essential to elucidate the normal-state and superconducting properties of the iron-based superconductors. Because these materials are mostly metallic, a good starting point is an effective low-energy model that captures the electronic states near the Fermi level and their interactions. However, in contrast to cuprates, iron-based high-T c compounds are multi-orbital systems with Hubbard and Hund interactions, resulting in a rather involved 10-orbital lattice model. Here we review different minimal models that have been proposed to unveil the universal features of these systems. We first review minimal models defined solely in the orbital basis, which focus on a particular subspace of orbitals, or solely in the band basis, which rely only on the geometry of the Fermi surface. The former, while providing important qualitative insight into the role of the orbital degrees of freedom, do not distinguish between high-energy and low-energy sectors and, for this reason, generally do not go beyond mean-field. The latter allow one to go beyond mean-field and investigate the interplay between superconducting and magnetic orders as well as Ising-nematic order. However, they cannot capture orbital-dependent features like spontaneous orbital order. We then review recent proposals for a minimal model that operates in the band basis but fully incorporates the orbital composition and symmetries of the low-energy excitations. We discuss the results of the renormalization group study of such a model, particularly of the interplay between superconductivity, magnetism, and spontaneous orbital order, and compare theoretical predictions with experiments on iron pnictides and chalcogenides. We also discuss the impact of the glide-plane symmetry on the low-energy models, highlighting the key role played by the spin-orbit coupling.
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29
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Liu M, Sternbach AJ, Basov DN. Nanoscale electrodynamics of strongly correlated quantum materials. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:014501. [PMID: 27811387 DOI: 10.1088/0034-4885/80/1/014501] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Electronic, magnetic, and structural phase inhomogeneities are ubiquitous in strongly correlated quantum materials. The characteristic length scales of the phase inhomogeneities can range from atomic to mesoscopic, depending on their microscopic origins as well as various sample dependent factors. Therefore, progress with the understanding of correlated phenomena critically depends on the experimental techniques suitable to provide appropriate spatial resolution. This requirement is difficult to meet for some of the most informative methods in condensed matter physics, including infrared and optical spectroscopy. Yet, recent developments in near-field optics and imaging enabled a detailed characterization of the electromagnetic response with a spatial resolution down to 10 nm. Thus it is now feasible to exploit at the nanoscale well-established capabilities of optical methods for characterization of electronic processes and lattice dynamics in diverse classes of correlated quantum systems. This review offers a concise description of the state-of-the-art near-field techniques applied to prototypical correlated quantum materials. We also discuss complementary microscopic and spectroscopic methods which reveal important mesoscopic dynamics of quantum materials at different energy scales.
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Affiliation(s)
- Mengkun Liu
- Department of Physics, Stony Brook University, Stony Brook, NY 11794, USA
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30
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Ziatdinov M, Maksov A, Li L, Sefat AS, Maksymovych P, Kalinin SV. Deep data mining in a real space: separation of intertwined electronic responses in a lightly doped BaFe 2As 2. NANOTECHNOLOGY 2016; 27:475706. [PMID: 27780159 DOI: 10.1088/0957-4484/27/47/475706] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Electronic interactions present in material compositions close to the superconducting dome play a key role in the manifestation of high-T c superconductivity. In many correlated electron systems, however, the parent or underdoped states exhibit strongly inhomogeneous electronic landscape at the nanoscale that may be associated with competing, coexisting, or intertwined chemical disorder, strain, magnetic, and structural order parameters. Here we demonstrate an approach based on a combination of scanning tunneling microscopy/spectroscopy and advanced statistical learning for an automatic separation and extraction of statistically significant electronic behaviors in the spin density wave regime of a lightly (∼1%) gold-doped BaFe2As2. We show that the decomposed STS spectral features have a direct relevance to fundamental physical properties of the system, such as SDW-induced gap, pseudogap-like state, and impurity resonance states.
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Affiliation(s)
- Maxim Ziatdinov
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. ORNL Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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32
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Tao J, Sun K, Yin WG, Wu L, Xin H, Wen JG, Luo W, Pennycook SJ, Tranquada JM, Zhu Y. Direct observation of electronic-liquid-crystal phase transitions and their microscopic origin in La 1/3Ca 2/3MnO 3. Sci Rep 2016; 6:37624. [PMID: 27874069 PMCID: PMC5118726 DOI: 10.1038/srep37624] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 10/14/2016] [Indexed: 11/18/2022] Open
Abstract
The ground-state electronic order in doped manganites is frequently associated with a lattice modulation, contributing to their many interesting properties. However, measuring the thermal evolution of the lattice superstructure with reciprocal-space probes alone can lead to ambiguous results with competing interpretations. Here we provide direct observations of the evolution of the superstructure in La1/3Ca2/3MnO3 in real space, as well as reciprocal space, using transmission electron microscopic (TEM) techniques. We show that the transitions are the consequence of a proliferation of dislocations plus electronic phase separation. The resulting states are well described by the symmetries associated with electronic-liquid-crystal (ELC) phases. Moreover, our results resolve the long-standing controversy over the origin of the incommensurate superstructure and suggest a new structural model that is consistent with recent theoretical calculations.
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Affiliation(s)
- J. Tao
- Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - K. Sun
- Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA
| | - W.-G. Yin
- Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - L. Wu
- Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - H. Xin
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - J. G. Wen
- Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA
| | - W. Luo
- Department of Physics & Astronomy, Shanghai JiaoTong University, Shanghai, China
| | - S. J. Pennycook
- Department of Materials Science and Engineering, National University of Singapore, 119077 Singapore
| | - J. M. Tranquada
- Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Y. Zhu
- Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
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33
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Feldman BE, Randeria MT, Gyenis A, Wu F, Ji H, Cava RJ, MacDonald AH, Yazdani A. Observation of a nematic quantum Hall liquid on the surface of bismuth. Science 2016; 354:316-321. [DOI: 10.1126/science.aag1715] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 09/23/2016] [Indexed: 11/02/2022]
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34
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Macdonald AJ, Tremblay-Johnston YS, Grothe S, Chi S, Dosanjh P, Johnston S, Burke SA. Dispersing artifacts in FT-STS: a comparison of set point effects across acquisition modes. NANOTECHNOLOGY 2016; 27:414004. [PMID: 27607539 DOI: 10.1088/0957-4484/27/41/414004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Fourier-transform scanning tunnelling spectroscopy (FT-STS), or quasiparticle interference, has become an influential tool for the study of a wide range of important materials in condensed matter physics. However, FT-STS in complex materials is often challenging to interpret, requiring significant theoretical input in many cases, making it crucial to understand potential artifacts of the measurement. Here, we compare the most common modes of acquiring FT-STS data and show through both experiment and simulations that artifact features can arise that depend on how the tip height is stabilized throughout the course of the measurement. The most dramatic effect occurs when a series of dI/dV maps at different energies are acquired with simultaneous constant current feedback; here a feature that disperses in energy appears that is not observed in other measurement modes. Such artifact features are similar to those arising from real physical processes in the sample and are susceptible to misinterpretation.
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Affiliation(s)
- A J Macdonald
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada V6T 1Z1. Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
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35
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Kuo HH, Chu JH, Palmstrom JC, Kivelson SA, Fisher IR. Ubiquitous signatures of nematic quantum criticality in optimally doped Fe-based superconductors. Science 2016; 352:958-62. [DOI: 10.1126/science.aab0103] [Citation(s) in RCA: 201] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 04/15/2016] [Indexed: 11/02/2022]
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36
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Wang Y, Moritz B, Chen CC, Jia CJ, van Veenendaal M, Devereaux TP. Using Nonequilibrium Dynamics to Probe Competing Orders in a Mott-Peierls System. PHYSICAL REVIEW LETTERS 2016; 116:086401. [PMID: 26967429 DOI: 10.1103/physrevlett.116.086401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Indexed: 06/05/2023]
Abstract
Competition between ordered phases, and their associated phase transitions, are significant in the study of strongly correlated systems. Here, we examine one aspect, the nonequilibrium dynamics of a photoexcited Mott-Peierls system, using an effective Peierls-Hubbard model and exact diagonalization. Near a transition where spin and charge become strongly intertwined, we observe antiphase dynamics and a coupling-strength-dependent suppression or enhancement in the static structure factors. The renormalized bosonic excitations coupled to a particular photoexcited electron can be extracted, which provides an approach for characterizing the underlying bosonic modes. The results from this analysis for different electronic momenta show an uneven softening due to a stronger coupling near k_{F}. This behavior reflects the strong link between the fermionic momenta, the coupling vertices, and ultimately, the bosonic susceptibilities when multiple phases compete for the ground state of the system.
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Affiliation(s)
- Y Wang
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
- SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - B Moritz
- SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Department of Physics and Astrophysics, University of North Dakota, Grand Forks, North Dakota 58202, USA
| | - C-C Chen
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - C J Jia
- SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - M van Veenendaal
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
- Department of Physics, Northern Illinois University, De Kalb, Illinois 60115, USA
| | - T P Devereaux
- SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
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37
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Wang Q, Shen Y, Pan B, Hao Y, Ma M, Zhou F, Steffens P, Schmalzl K, Forrest TR, Abdel-Hafiez M, Chen X, Chareev DA, Vasiliev AN, Bourges P, Sidis Y, Cao H, Zhao J. Strong interplay between stripe spin fluctuations, nematicity and superconductivity in FeSe. NATURE MATERIALS 2016; 15:159-163. [PMID: 26641018 DOI: 10.1038/nmat4492] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 10/26/2015] [Indexed: 06/05/2023]
Abstract
In iron-based superconductors the interactions driving the nematic order (that breaks four-fold rotational symmetry in the iron plane) may also mediate the Cooper pairing. The experimental determination of these interactions, which are believed to depend on the orbital or the spin degrees of freedom, is challenging because nematic order occurs at, or slightly above, the ordering temperature of a stripe magnetic phase. Here, we study FeSe (ref. )-which exhibits a nematic (orthorhombic) phase transition at Ts = 90 K without antiferromagnetic ordering-by neutron scattering, finding substantial stripe spin fluctuations coupled with the nematicity that are enhanced abruptly on cooling through Ts. A sharp spin resonance develops in the superconducting state, whose energy (∼4 meV) is consistent with an electron-boson coupling mode revealed by scanning tunnelling spectroscopy. The magnetic spectral weight in FeSe is found to be comparable to that of the iron arsenides. Our results support recent theoretical proposals that both nematicity and superconductivity are driven by spin fluctuations.
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Affiliation(s)
- Qisi Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yao Shen
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Bingying Pan
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yiqing Hao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Mingwei Ma
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100190, China
| | - Fang Zhou
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100190, China
| | - P Steffens
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble Cedex 9, France
| | - K Schmalzl
- Juelich Centre for Neutron Science JCNS Forschungszentrum Juelich GmbH, Outstation at ILL, 38042 Grenoble, France
| | - T R Forrest
- European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex, France
| | - M Abdel-Hafiez
- Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China
- Faculty of Science, Physics Department, Fayoum University, 63514 Fayoum, Egypt
| | - Xiaojia Chen
- Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China
| | - D A Chareev
- Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, Moscow District 142432, Russia
| | - A N Vasiliev
- Low Temperature Physics and Superconductivity Department, M.V. Lomonosov Moscow State University, Moscow 119991, Russia
- Theoretical Physics and Applied Mathematics Department, Ural Federal University, Ekaterinburg 620002, Russia
- National University of Science and Technology "MISiS", Moscow 119049, Russia
| | - P Bourges
- Laboratoire Leon Brillouin, CEA-CNRS, CEA-Saclay, 91191 Gif sur Yvette, France
| | - Y Sidis
- Laboratoire Leon Brillouin, CEA-CNRS, CEA-Saclay, 91191 Gif sur Yvette, France
| | - Huibo Cao
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393, USA
| | - Jun Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, China
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Liquid crystal phases of two-dimensional dipolar gases and Berezinskii-Kosterlitz-Thouless melting. Sci Rep 2016; 6:19038. [PMID: 26750156 PMCID: PMC4707468 DOI: 10.1038/srep19038] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 12/03/2015] [Indexed: 11/08/2022] Open
Abstract
Liquid crystals are phases of matter intermediate between crystals and liquids. Whereas classical liquid crystals have been known for a long time and are used in electro-optical displays, much less is known about their quantum counterparts. There is growing evidence that quantum liquid crystals play a central role in many electron systems including high temperature superconductors, but a quantitative understanding is lacking due to disorder and other complications. Here, we analyse the quantum phase diagram of a two-dimensional dipolar gas, which exhibits stripe, nematic and supersolid phases. We calculate the stiffness constants determining the stability of the nematic and stripe phases, and the melting of the stripes set by the proliferation of topological defects is analysed microscopically. Our results for the critical temperatures of these phases demonstrate that a controlled study of the interplay between quantum liquid and superfluid phases is within experimental reach for the first time, using dipolar gases.
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39
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Gallais Y, Paul I, Chauvière L, Schmalian J. Nematic Resonance in the Raman Response of Iron-Based Superconductors. PHYSICAL REVIEW LETTERS 2016; 116:017001. [PMID: 26799039 DOI: 10.1103/physrevlett.116.017001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Indexed: 06/05/2023]
Abstract
In a fully gapped superconductor the electronic Raman response has a pair-breaking peak at twice the superconducting gap Δ, if the Bogoliubov excitations are uncorrelated. Motivated by the iron based superconductors, we study how this peak is modified if the superconducting phase hosts a nematic-structural quantum critical point. We show that, upon approaching this point by tuning, e.g., doping, the growth of nematic correlations between the quasiparticles transforms the pair-breaking peak into a nematic resonance. The mode energy is below 2Δ, and stays finite at the quantum critical point, where its spectral weight is sharply enhanced. The latter is consistent with recent experiments on electron-doped iron based superconductors and provides direct evidence of nematic correlations in their superconducting phases.
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Affiliation(s)
- Yann Gallais
- Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - Indranil Paul
- Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - Ludivine Chauvière
- Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS, Université Paris Diderot, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - Jörg Schmalian
- Institute for Theory of Condensed Matter, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
- Institute for Solid State Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
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40
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Singh UR, White SC, Schmaus S, Tsurkan V, Loidl A, Deisenhofer J, Wahl P. Evidence for orbital order and its relation to superconductivity in FeSe0.4Te0.6. SCIENCE ADVANCES 2015; 1:e1500206. [PMID: 26601277 PMCID: PMC4646791 DOI: 10.1126/sciadv.1500206] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 09/02/2015] [Indexed: 06/05/2023]
Abstract
The emergence of nematic electronic states accompanied by a structural phase transition is a recurring theme in many correlated electron materials, including the high-temperature copper oxide- and iron-based superconductors. We provide evidence for nematic electronic states in the iron-chalcogenide superconductor FeSe0.4Te0.6 from quasi-particle scattering detected in spectroscopic maps. The symmetry-breaking states persist above T c into the normal state. We interpret the scattering patterns by comparison with quasi-particle interference patterns obtained from a tight-binding model, accounting for orbital ordering. The relation to superconductivity and the influence on the coherence length are discussed.
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Affiliation(s)
- Udai R. Singh
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Seth C. White
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Stefan Schmaus
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Vladimir Tsurkan
- Center for Electronic Correlations and Magnetism, Experimental Physics V, University of Augsburg, D-86159 Augsburg, Germany
- Institute of Applied Physics, Academy of Sciences of Moldova, MD 2028 Chisinau, Republic of Moldova
| | - Alois Loidl
- Center for Electronic Correlations and Magnetism, Experimental Physics V, University of Augsburg, D-86159 Augsburg, Germany
| | - Joachim Deisenhofer
- Center for Electronic Correlations and Magnetism, Experimental Physics V, University of Augsburg, D-86159 Augsburg, Germany
| | - Peter Wahl
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK
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41
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Mirri C, Dusza A, Bastelberger S, Chinotti M, Degiorgi L, Chu JH, Kuo HH, Fisher IR. Origin of the Resistive Anisotropy in the Electronic Nematic Phase of BaFe(2)As(2) Revealed by Optical Spectroscopy. PHYSICAL REVIEW LETTERS 2015; 115:107001. [PMID: 26382696 DOI: 10.1103/physrevlett.115.107001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Indexed: 06/05/2023]
Abstract
We perform, as a function of uniaxial stress, an optical-reflectivity investigation of the representative "parent" ferropnictide BaFe(2)As(2) in a broad spectral range, across the tetragonal-to-orthorhombic phase transition and the onset of the long-range antiferromagnetic (AFM) order. The infrared response reveals that the dc transport anisotropy in the orthorhombic AFM state is determined by the interplay between the Drude spectral weight and the scattering rate, but that the dominant effect is clearly associated with the metallic spectral weight. In the paramagnetic tetragonal phase, though, the dc resistivity anisotropy of strained samples is almost exclusively due to stress-induced changes in the Drude weight rather than in the scattering rate, definitively establishing the anisotropy of the Fermi surface parameters as the primary effect driving the dc transport properties in the electronic nematic state.
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Affiliation(s)
- C Mirri
- Laboratorium für Festkörperphysik, ETH-Zürich, 8093 Zürich, Switzerland
| | - A Dusza
- Laboratorium für Festkörperphysik, ETH-Zürich, 8093 Zürich, Switzerland
| | - S Bastelberger
- Laboratorium für Festkörperphysik, ETH-Zürich, 8093 Zürich, Switzerland
| | - M Chinotti
- Laboratorium für Festkörperphysik, ETH-Zürich, 8093 Zürich, Switzerland
| | - L Degiorgi
- Laboratorium für Festkörperphysik, ETH-Zürich, 8093 Zürich, Switzerland
| | - J-H Chu
- Geballe Laboratory for Advanced Materials and Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - H-H Kuo
- Geballe Laboratory for Advanced Materials and Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - I R Fisher
- Geballe Laboratory for Advanced Materials and Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
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42
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Richard P, Qian T, Ding H. ARPES measurements of the superconducting gap of Fe-based superconductors and their implications to the pairing mechanism. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:293203. [PMID: 26153847 DOI: 10.1088/0953-8984/27/29/293203] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Its direct momentum sensitivity confers to angle-resolved photoemission spectroscopy (ARPES) a unique perspective in investigating the superconducting gap of multi-band systems. In this review we discuss ARPES studies on the superconducting gap of high-temperature Fe-based superconductors. We show that while Fermi-surface-driven pairing mechanisms fail to provide a universal scheme for the Fe-based superconductors, theoretical approaches based on short-range interactions lead to a more robust and universal description of superconductivity in these materials. Our findings are also discussed in the broader context of unconventional superconductivity.
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Affiliation(s)
- P Richard
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China. Collaborative Innovation Center of Quantum Matter, Beijing, People's Republic of China
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Wang Z, Nevidomskyy AH. Orbital nematic order and interplay with magnetism in the two-orbital Hubbard model. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:225602. [PMID: 25988222 DOI: 10.1088/0953-8984/27/22/225602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Motivated by the recent angle-resolved photoemission spectroscopy (ARPES) on FeSe and iron pnictide families of iron-based superconductors, we have studied the orbital nematic order and its interplay with antiferromagnetism within the two-orbital Hubbard model. We used random phase approximation (RPA) to calculate the dependence of the orbital and magnetic susceptibilities on the strength of interactions and electron density (doping). To account for strong electron correlations not captured by RPA, we further employed non-perturbative variational cluster approximation (VCA) capable of capturing symmetry broken magnetic and orbitally ordered phases. Both approaches show that the electron and hole doping affect the two orders differently. While hole doping tends to suppress both magnetism and orbital ordering, the electron doping suppresses magnetism faster. Crucially, we find a realistic parameter regime for moderate electron doping that stabilizes orbital nematicity in the absence of long-range antiferromagnetic order. This is reminiscent of the non-magnetic orbital nematic phase observed recently in FeSe and a number of iron pnictide materials and raises the possibility that at least in some cases, the observed electronic nematicity may be primarily due to orbital rather than magnetic fluctuations.
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Affiliation(s)
- Zhentao Wang
- Department of Physics and Astronomy, Rice University, Houston, TX 77005, USA
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44
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Johnson PD, Yang HB, Rameau JD, Gu GD, Pan ZH, Valla T, Weinert M, Fedorov AV. Spin-orbit interactions and the nematicity observed in the fe-based superconductors. PHYSICAL REVIEW LETTERS 2015; 114:167001. [PMID: 25955070 DOI: 10.1103/physrevlett.114.167001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2014] [Indexed: 06/04/2023]
Abstract
High-resolution angle-resolved photoelectron spectroscopy is used to examine the electronic band structure of FeTe_{0.5}Se_{0.5} near the Brillouin zone center. A consistent separation of the α_{1} and α_{2} bands is observed with little k_{z} dependence of the α_{1} band. First-principles calculations for bulk and thin films demonstrate that the antiferromagnetic coupling between the Fe atoms and hybridization-induced spin-orbit effects lifts the degeneracy of the Fe d_{xz} and d_{yz} orbitals at the zone center leading to orbital ordering. These experimental and computational results provide a natural microscopic basis for the nematicity observed in the Fe-based superconductors.
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Affiliation(s)
- P D Johnson
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - H-B Yang
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - J D Rameau
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - G D Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Z-H Pan
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - T Valla
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - M Weinert
- Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA
| | - A V Fedorov
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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45
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Su Y, Liao H, Li T. The form and origin of orbital ordering in the electronic nematic phase of iron-based superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:105702. [PMID: 25710728 DOI: 10.1088/0953-8984/27/10/105702] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We investigated the form of orbital ordering in the electronic nematic phase of iron-based superconductors by applying a group theoretical analysis on a realistic five-band model. We find the orbital order can be either of the inter-orbital s-wave form or intra-orbital d-waveform. From the comparison with existing ARPES measurements of band splitting, we find the orbital ordering in the 122 system is dominated by an intra-orbital d-wave component, while that of the 111 system is dominated by an inter-orbital s-wave component. We find both forms of orbital order are strongly entangled with the nematicity in the spin correlation of the system.The condensation energy of the magnetic ordered phase is found to be significantly improved (by more than 20%) when the degeneracy between the (π, 0) and (0, π) ordering pattern is lifted by the orbital order. We argue there should be a large difference in both the scattering rate and the size of the possible pseudogap on the electron pocket around the X = (π, 0) and Y = (0, π) point in the electronic nematic phase. We propose this as a possible origin for the observed nematicity in resistivity measurements.
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Affiliation(s)
- Yuehua Su
- Department of Physics, Yantai University, Yantai 264005, People’s Republic of China
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46
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Wang Y, Gastiasoro MN, Andersen BM, Tomić M, Jeschke HO, Valentí R, Paul I, Hirschfeld PJ. Effects of Lifshitz transition on charge transport in magnetic phases of Fe-based superconductors. PHYSICAL REVIEW LETTERS 2015; 114:097003. [PMID: 25793844 DOI: 10.1103/physrevlett.114.097003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Indexed: 06/04/2023]
Abstract
The unusual temperature dependence of the resistivity and its in-plane anisotropy observed in the Fe-based superconducting materials, particularly Ba(Fe_{1-x}Co_{x})_{2}As_{2}, has been a long-standing puzzle. Here, we consider the effect of impurity scattering on the temperature dependence of the average resistivity within a simple two-band model of a dirty spin density wave metal. The sharp drop in resistivity below the Néel temperature T_{N} in the parent compound can only be understood in terms of a Lifshitz transition following Fermi surface reconstruction upon magnetic ordering. We show that the observed resistivity anisotropy in this phase, arising from nematic defect structures, is affected by the Lifshitz transition as well.
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Affiliation(s)
- Y Wang
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
| | - Maria N Gastiasoro
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Brian M Andersen
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - M Tomić
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
| | - Harald O Jeschke
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
| | - Indranil Paul
- Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Diderot-Paris VII & CNRS, UMR 7162, 75205 Paris, France
| | - P J Hirschfeld
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
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Zhang Q, Fernandes RM, Lamsal J, Yan J, Chi S, Tucker GS, Pratt DK, Lynn JW, McCallum RW, Canfield PC, Lograsso TA, Goldman AI, Vaknin D, McQueeney RJ. Neutron-scattering measurements of spin excitations in LaFeAsO and Ba(Fe(0.953)Co(0.047))(2)As(2): evidence for a sharp enhancement of spin fluctuations by nematic order. PHYSICAL REVIEW LETTERS 2015; 114:057001. [PMID: 25699463 DOI: 10.1103/physrevlett.114.057001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Indexed: 06/04/2023]
Abstract
Inelastic neutron scattering is employed to investigate the impact of electronic nematic order on the magnetic spectra of LaFeAsO and Ba(Fe(0.953)Co(0.047))(2)As(2). These materials are ideal to study the paramagnetic-nematic state, since the nematic order, signaled by the tetragonal-to-orthorhombic transition at T(S), sets in well above the stripe antiferromagnetic ordering at T(N). We find that the temperature-dependent dynamic susceptibility displays an anomaly at T(S) followed by a sharp enhancement in the spin-spin correlation length, revealing a strong feedback effect of nematic order on the low-energy magnetic spectrum. Our findings can be consistently described by a model that attributes the structural or nematic transition to magnetic fluctuations, and unveils the key role played by nematic order in promoting the long-range stripe antiferromagnetic order in iron pnictides.
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Affiliation(s)
- Qiang Zhang
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Rafael M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Jagat Lamsal
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Jiaqiang Yan
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Songxue Chi
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Gregory S Tucker
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Daniel K Pratt
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
| | - Jeffrey W Lynn
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
| | - R W McCallum
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Materials Sciences and Engineering, Iowa State University, Ames, Iowa 50011, USA
| | - Paul C Canfield
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Thomas A Lograsso
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Materials Sciences and Engineering, Iowa State University, Ames, Iowa 50011, USA
| | - Alan I Goldman
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - David Vaknin
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Robert J McQueeney
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA and Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Intra-unit-cell nematic charge order in the titanium-oxypnictide family of superconductors. Nat Commun 2014; 5:5761. [PMID: 25482113 DOI: 10.1038/ncomms6761] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 11/05/2014] [Indexed: 11/08/2022] Open
Abstract
Understanding the role played by broken-symmetry states such as charge, spin and orbital orders in the mechanism of emergent properties, such as high-temperature superconductivity, is a major current topic in materials research. That the order may be within one unit cell, such as nematic, was only recently considered theoretically, but its observation in the iron-pnictide and doped cuprate superconductors places it at the forefront of current research. Here, we show that the recently discovered BaTi2Sb2O superconductor and its parent compound BaTi2As2O form a symmetry-breaking nematic ground state that can be naturally explained as an intra-unit-cell nematic charge order with d-wave symmetry, pointing to the ubiquity of the phenomenon. These findings, together with the key structural features in these materials being intermediate between the cuprate and iron-pnictide high-temperature superconducting materials, render the titanium oxypnictides an important new material system to understand the nature of nematic order and its relationship to superconductivity.
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Nakayama K, Miyata Y, Phan GN, Sato T, Tanabe Y, Urata T, Tanigaki K, Takahashi T. Reconstruction of band structure induced by electronic nematicity in an FeSe superconductor. PHYSICAL REVIEW LETTERS 2014; 113:237001. [PMID: 25526150 DOI: 10.1103/physrevlett.113.237001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Indexed: 06/04/2023]
Abstract
We have performed high-resolution angle-resolved photoemission spectroscopy on an FeSe superconductor (T_{c}∼8 K), which exhibits a tetragonal-to-orthorhombic structural transition at T_{s}∼90 K. At low temperature, we found splitting of the energy bands as large as 50 meV at the M point in the Brillouin zone, likely caused by the formation of electronically driven nematic states. This band splitting persists up to T∼110 K, slightly above T_{s}, suggesting that the structural transition is triggered by the electronic nematicity. We have also revealed that at low temperature the band splitting gives rise to a van Hove singularity within 5 meV of the Fermi energy. The present result strongly suggests that this unusual electronic state is responsible for the unconventional superconductivity in FeSe.
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Affiliation(s)
- K Nakayama
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - Y Miyata
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - G N Phan
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - T Sato
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - Y Tanabe
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - T Urata
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - K Tanigaki
- Department of Physics, Tohoku University, Sendai 980-8578, Japan and WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - T Takahashi
- Department of Physics, Tohoku University, Sendai 980-8578, Japan and WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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50
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Gastiasoro MN, Paul I, Wang Y, Hirschfeld PJ, Andersen BM. Emergent defect states as a source of resistivity anisotropy in the nematic phase of iron pnictides. PHYSICAL REVIEW LETTERS 2014; 113:127001. [PMID: 25279638 DOI: 10.1103/physrevlett.113.127001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Indexed: 06/03/2023]
Abstract
We consider the role of potential scatterers in the nematic phase of Fe-based superconductors above the transition temperature to the (π, 0) magnetic state but below the orthorhombic structural transition. The anisotropic spin fluctuations in this region can be frozen by disorder, to create elongated magnetic droplets whose anisotropy grows as the magnetic transition is approached. Such states act as strong anisotropic defect potentials that scatter with much higher probability perpendicular to their length than parallel, although the actual crystal symmetry breaking is tiny. We calculate the scattering potentials, relaxation rates, and conductivity in this region and show that such emergent defect states are essential for the transport anisotropy observed in experiments.
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Affiliation(s)
- Maria N Gastiasoro
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - I Paul
- Laboratoire Matériaux et Phénomènes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - Y Wang
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
| | - P J Hirschfeld
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
| | - Brian M Andersen
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
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