1
|
Hu LH, Zhang RX. Dislocation Majorana bound states in iron-based superconductors. Nat Commun 2024; 15:2337. [PMID: 38491015 PMCID: PMC10943028 DOI: 10.1038/s41467-024-46618-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Accepted: 03/04/2024] [Indexed: 03/18/2024] Open
Abstract
We show that lattice dislocations of topological iron-based superconductors such as FeTe1-xSex will intrinsically trap non-Abelian Majorana quasiparticles, in the absence of any external magnetic field. Our theory is motivated by the recent experimental observations of normal-state weak topology and surface magnetism that coexist with superconductivity in FeTe1-xSex, the combination of which naturally achieves an emergent second-order topological superconductivity in a two-dimensional subsystem spanned by screw or edge dislocations. This exemplifies a new embedded higher-order topological phase in class D, where Majorana zero modes appear around the "corners" of a low-dimensional embedded subsystem, instead of those of the full crystal. A nested domain wall theory is developed to understand the origin of these defect Majorana zero modes. When the surface magnetism is absent, we further find that s± pairing symmetry itself is capable of inducing a different type of class-DIII embedded higher-order topology with defect-bound Majorana Kramers pairs. We also provide detailed discussions on the real-world material candidates for our proposals, including FeTe1-xSex, LiFeAs, β-PdBi2, and heterostructures of bismuth, etc. Our work establishes lattice defects as a new venue to achieve high-temperature topological quantum information processing.
Collapse
Affiliation(s)
- Lun-Hui Hu
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, USA
- Institute for Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, TN, USA
- Center for Correlated Matter and School of Physics, Zhejiang University, Hangzhou, China
| | - Rui-Xing Zhang
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, USA.
- Institute for Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, TN, USA.
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, USA.
| |
Collapse
|
2
|
Multiple Andreev reflections effect spectroscopy of LiFeAs single crystals: three superconducting order parameters and their temperature evolution. SN APPLIED SCIENCES 2022. [DOI: 10.1007/s42452-022-05057-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
AbstractThe structure of the superconducting order parameter of LiFeAs is studied by incoherent multiple Andreev reflections effect (IMARE) spectroscopy. The high transparent superconductor–thin normal metal–superconductor (SnS) contacts are created by a planar “break-junction” technique. Below $$T_c \approx 17.5$$
T
c
≈
17.5
K, the obtained I(V) and dI(V)/dV characteristics of SnS junctions show a presence of at least three bulk superconducting order parameters in LiFeAs. We directly determine the magnitudes, characteristic ratios, and temperature dependences of the superconducting gaps and discuss their symmetry.
Collapse
|
3
|
Cao L, Liu W, Li G, Dai G, Zheng Q, Wang Y, Jiang K, Zhu S, Huang L, Kong L, Yang F, Wang X, Zhou W, Lin X, Hu J, Jin C, Ding H, Gao HJ. Two distinct superconducting states controlled by orientations of local wrinkles in LiFeAs. Nat Commun 2021; 12:6312. [PMID: 34728627 PMCID: PMC8563765 DOI: 10.1038/s41467-021-26708-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 10/14/2021] [Indexed: 11/30/2022] Open
Abstract
For iron-based superconductors, the phase diagrams under pressure or strain exhibit emergent phenomena between unconventional superconductivity and other electronic orders, varying in different systems. As a stoichiometric superconductor, LiFeAs has no structure phase transitions or entangled electronic states, which manifests an ideal platform to explore the pressure or strain effect on unconventional superconductivity. Here, we observe two types of superconducting states controlled by orientations of local wrinkles on the surface of LiFeAs. Using scanning tunneling microscopy/spectroscopy, we find type-I wrinkles enlarge the superconducting gaps and enhance the transition temperature, whereas type-II wrinkles significantly suppress the superconducting gaps. The vortices on wrinkles show a C2 symmetry, indicating the strain effects on the wrinkles. By statistics, we find that the two types of wrinkles are categorized by their orientations. Our results demonstrate that the local strain effect with different directions can tune the superconducting order parameter of LiFeAs very differently, suggesting that the band shifting induced by directional pressure may play an important role in iron-based superconductivity. The evolution of superconductivity in LiFeAs with respect to pressure or strain remains elusive. Here, the authors observe different response of superconducting states due to different orientations of local wrinkles on the surface of LiFeAs.
Collapse
Affiliation(s)
- Lu Cao
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wenyao Liu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Geng Li
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China. .,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China. .,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China. .,Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China.
| | - Guangyang Dai
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Qi Zheng
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yuxin Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Kun Jiang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shiyu Zhu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Li Huang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Lingyuan Kong
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Fazhi Yang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiancheng Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China.,Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Wu Zhou
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Xiao Lin
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jiangping Hu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Changqing Jin
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China.,Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Hong Ding
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China. .,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China. .,Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China.
| | - Hong-Jun Gao
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China. .,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China. .,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China. .,Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China.
| |
Collapse
|
4
|
Kong L, Cao L, Zhu S, Papaj M, Dai G, Li G, Fan P, Liu W, Yang F, Wang X, Du S, Jin C, Fu L, Gao HJ, Ding H. Majorana zero modes in impurity-assisted vortex of LiFeAs superconductor. Nat Commun 2021; 12:4146. [PMID: 34230479 PMCID: PMC8260634 DOI: 10.1038/s41467-021-24372-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 06/10/2021] [Indexed: 11/29/2022] Open
Abstract
The iron-based superconductor is emerging as a promising platform for Majorana zero mode, which can be used to implement topological quantum computation. One of the most significant advances of this platform is the appearance of large vortex level spacing that strongly protects Majorana zero mode from other low-lying quasiparticles. Despite the advantages in the context of physics research, the inhomogeneity of various aspects hampers the practical construction of topological qubits in the compounds studied so far. Here we show that the stoichiometric superconductor LiFeAs is a good candidate to overcome this obstacle. By using scanning tunneling microscopy, we discover that the Majorana zero modes, which are absent on the natural clean surface, can appear in vortices influenced by native impurities. Our detailed analysis reveals a new mechanism for the emergence of those Majorana zero modes, i.e. native tuning of bulk Dirac fermions. The discovery of Majorana zero modes in this homogeneous material, with a promise of tunability, offers an ideal material platform for manipulating and braiding Majorana zero modes, pushing one step forward towards topological quantum computation. Despite the discovery of Majorana zero modes (MZM) in iron-based superconductors, sample inhomogeneity may destroy MZMs during braiding. Here, authors observe MZM in impurity-assisted vortices due to tuning of the bulk Dirac fermions in a homogeneous superconductor LiFeAs.
Collapse
Affiliation(s)
- Lingyuan Kong
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Lu Cao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Shiyu Zhu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Michał Papaj
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Guangyang Dai
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Geng Li
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Peng Fan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Wenyao Liu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Fazhi Yang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Xiancheng Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Shixuan Du
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China.,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, China
| | - Changqing Jin
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China.,Songshan Lake Materials Laboratory, Dongguan, Guangdong, China
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Hong-Jun Gao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China. .,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China. .,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, China.
| | - Hong Ding
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China. .,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, China. .,Songshan Lake Materials Laboratory, Dongguan, Guangdong, China.
| |
Collapse
|
5
|
Han TT, Chen L, Cai C, Wang YD, Wang ZG, Xin ZM, Zhang Y. Isostructural Spin-Density-Wave and Superconducting Gap Anisotropies in Iron-Arsenide Superconductors. PHYSICAL REVIEW LETTERS 2020; 124:247002. [PMID: 32639832 DOI: 10.1103/physrevlett.124.247002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 06/01/2020] [Indexed: 06/11/2023]
Abstract
When passing through a phase transition, electronic system saves energy by opening energy gaps at the Fermi level. Delineating the energy gap anisotropy provides insights into the origin of the interactions that drive the phase transition. Here, we report the angle-resolved photoemission spectroscopy (ARPES) study on the detailed gap anisotropies in both the tetragonal magnetic and superconducting phases in Sr_{1-x}Na_{x}Fe_{2}As_{2}. First, we found that the spin-density-wave (SDW) gap is strongly anisotropic in the tetragonal magnetic phase. The gap magnitude correlates with the orbital character of Fermi surface closely. Second, we found that the SDW gap anisotropy is isostructural to the superconducting gap anisotropy regarding to the angular dependence, gap minima locations, and relative gap magnitudes. Our results indicate that the superconducting pairing interaction and magnetic interaction share the same origin. The intraorbital scattering plays an important role in constructing these interactions resulting in the orbital-selective magnetism and superconductivity in iron-based superconductors.
Collapse
Affiliation(s)
- T T Han
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - L Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - C Cai
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Y D Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Z G Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Z M Xin
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Y Zhang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| |
Collapse
|
6
|
Superconducting-Gap Anisotropy of Iron Pnictides Investigated via Combinatorial Microwave Measurements. Sci Rep 2020; 10:7064. [PMID: 32341365 PMCID: PMC7184760 DOI: 10.1038/s41598-020-63304-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 03/20/2020] [Indexed: 12/03/2022] Open
Abstract
One of the most significant issues for superconductivity is clarifying the momentum-dependent superconducting gap Δ(\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${\boldsymbol{k}}$$\end{document}k), which is closely related to the pairing mechanism. To elucidate the gap structure, it is essential to investigate Δ(\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${\boldsymbol{k}}$$\end{document}k) in as many different physical quantities as possible and to crosscheck the results obtained in different methods with each other. In this paper, we report a combinatorial investigation of the superfluid density and the flux-flow resistivity of iron-pnictide superconductors; LiFeAs and BaFe2(As1−xPx)2 (x = 0.3, 0.45). We evaluated Δ(\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${\boldsymbol{k}}$$\end{document}k) by fitting these two-independent quantities with a two-band model simultaneously. The obtained Δ(\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${\boldsymbol{k}}$$\end{document}k) are consistent with the results observed in angle-resolved photoemission spectroscopy (ARPES) and scanning-tunneling spectroscopy (STS) studies. We believe our approach is a powerful method for investigating Δ(\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${\boldsymbol{k}}$$\end{document}k) because it does not require a sample with clean surface unlike ARPES and STS experiments, or a rotational magnetic-field system for direct measurements of the angular dependence of thermodynamic quantities.
Collapse
|
7
|
Yin JX, Zhang SS, Dai G, Zhao Y, Kreisel A, Macam G, Wu X, Miao H, Huang ZQ, Martiny JHJ, Andersen BM, Shumiya N, Multer D, Litskevich M, Cheng Z, Yang X, Cochran TA, Chang G, Belopolski I, Xing L, Wang X, Gao Y, Chuang FC, Lin H, Wang Z, Jin C, Bang Y, Hasan MZ. Quantum Phase Transition of Correlated Iron-Based Superconductivity in LiFe_{1-x}Co_{x}As. PHYSICAL REVIEW LETTERS 2019; 123:217004. [PMID: 31809171 DOI: 10.1103/physrevlett.123.217004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Indexed: 06/10/2023]
Abstract
The interplay between unconventional Cooper pairing and quantum states associated with atomic scale defects is a frontier of research with many open questions. So far, only a few of the high-temperature superconductors allow this intricate physics to be studied in a widely tunable way. We use scanning tunneling microscopy to image the electronic impact of Co atoms on the ground state of the LiFe_{1-x}Co_{x}As system. We observe that impurities progressively suppress the global superconducting gap and introduce low energy states near the gap edge, with the superconductivity remaining in the strong-coupling limit. Unexpectedly, the fully opened gap evolves into a nodal state before the Cooper pair coherence is fully destroyed. Our systematic theoretical analysis shows that these new observations can be quantitatively understood by the nonmagnetic Born-limit scattering effect in an s±-wave superconductor, unveiling the driving force of the superconductor to metal quantum phase transition.
Collapse
Affiliation(s)
- Jia-Xin Yin
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Songtian S Zhang
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Guangyang Dai
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yuanyuan Zhao
- School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China
| | - Andreas Kreisel
- Institut für Theoretische Physik, Universität Leipzig, D-04103 Leipzig, Germany
| | - Gennevieve Macam
- Department of Physics, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
| | - Xianxin Wu
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Institut für Theoretische Physik und Astrophysik, Julius-Maximilians-Universität Würzburg, 97074 Würzburg, Germany
| | - Hu Miao
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Zhi-Quan Huang
- Department of Physics, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
| | - Johannes H J Martiny
- Center for Nanostructured Graphene (CNG), Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Brian M Andersen
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Nana Shumiya
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Daniel Multer
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Maksim Litskevich
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Zijia Cheng
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Xian Yang
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Tyler A Cochran
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Guoqing Chang
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Ilya Belopolski
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Lingyi Xing
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiancheng Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yi Gao
- Center for Quantum Transport and Thermal Energy Science, Jiangsu Key Lab on Opto-Electronic Technology, School of Physics and Technology, Nanjing Normal University, Nanjing 210097, China
| | - Feng-Chuan Chuang
- Department of Physics, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
| | - Hsin Lin
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Ziqiang Wang
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Changqing Jin
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yunkyu Bang
- Asia Pacific Center for Theoretical Physics and Department of Physics, POSTECH, Pohang, Gyeongbuk, 790-784, Korea
| | - M Zahid Hasan
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| |
Collapse
|
8
|
Hong J. Analyzing scanning tunneling spectroscopy for Fe-based superconductors and extracting sample density of states. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:375602. [PMID: 31163407 DOI: 10.1088/1361-648x/ab26fb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We extract the density of states (DOS) from the scanning tunneling spectroscopy data for Ba1-x K x Fe2As2 superconductor. The obtained sample DOS is composed of two ordinary s-wave types from the band at [Formula: see text] point and a linear-like DOS within the s-wave gap from the band at M point in the Brillouin zone, and is consistent with the corresponding data from angle-resolved photoemission spectroscopy. We clarify that the major peak of the tunneling conductance is not related to the DOS but is rather the effect of nonequilibrium coherent tunneling including all coherent spins in the tip and sample.
Collapse
Affiliation(s)
- Jongbae Hong
- Research Institute of Basic Sciences, Incheon National University, Yeonsu-gu, Incheon 22012, Republic of Korea
| |
Collapse
|
9
|
Qin S, Hu L, Le C, Zeng J, Zhang FC, Fang C, Hu J. Quasi-1D Topological Nodal Vortex Line Phase in Doped Superconducting 3D Dirac Semimetals. PHYSICAL REVIEW LETTERS 2019; 123:027003. [PMID: 31386504 DOI: 10.1103/physrevlett.123.027003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 05/10/2019] [Indexed: 06/10/2023]
Abstract
We study vortex bound states in three-dimensional (3D) superconducting Dirac semimetals with time reversal symmetry. We find that there exist robust gapless vortex bound states propagating along the vortex line in the s-wave superconducting state. We refer to this newly found phase as the quasi-1D nodal vortex line phase. According to the Altland-Zirnbauer classification, the phase is characterized by a topological index (ν;N) at k_{z}=0 and k_{z}=π, where ν is the Z_{2} topological invariant for a 0D class-D system and N is the Z topological invariant for a 0D class-A system. Furthermore, we show that the vortex end Majorana zero mode can coexist with the quasi-1D nodal phase in certain types of Dirac semimetals. The possible experimental observations and material realization of such nodal vortex line states are discussed.
Collapse
Affiliation(s)
- Shengshan Qin
- Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Beijing National Research Center for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Lunhui Hu
- Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Department of Physics, University of California, San Diego, California 92093, USA
| | - Congcong Le
- Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Beijing National Research Center for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jinfeng Zeng
- Beijing National Research Center for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Science, Beijing 100049, China
| | - Fu-Chun Zhang
- Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Chen Fang
- Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Beijing National Research Center for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jiangping Hu
- Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Beijing National Research Center for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- South Bay Interdisciplinary Science Center, Dongguan, Guangdong Province, China
| |
Collapse
|
10
|
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.
Collapse
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.
| |
Collapse
|
11
|
Bang Y, Stewart GR. Superconducting properties of the s±-wave state: Fe-based superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:123003. [PMID: 28192286 DOI: 10.1088/1361-648x/aa564b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 12/20/2016] [Indexed: 06/06/2023]
Abstract
Although the pairing mechanism of Fe-based superconductors (FeSCs) has not yet been settled with consensus with regard to the pairing symmetry and the superconducting (SC) gap function, the vast majority of experiments support the existence of spin-singlet sign-changings-wave SC gaps on multi-bands (s±-wave state). This multi-bands±-wave state is a very unique gap stateper seand displays numerous unexpected novel SC properties, such as a strong reduction of the coherence peak, non-trivial impurity effects, nodal-gap-like nuclear magnetic resonance signals, various Volovik effects in the specific heat (SH) and thermal conductivity, and anomalous scaling behaviors with a SH jump and condensation energy versusTc, etc. In particular, many of these non-trivial SC properties can easily be mistaken as evidence for a nodal-gap state such as ad-wave gap. In this review, we provide detailed explanations of the theoretical principles for the various non-trivial SC properties of thes±-wave pairing state, and then critically compare the theoretical predictions with experiments on FeSCs. This will provide a pedagogical overview of to what extent we can coherently understand the wide range of different experiments on FeSCs within thes±-wave gap model.
Collapse
Affiliation(s)
- Yunkyu Bang
- Department of Physics, Chonnam National University, Kwangju 500-757, Republic of Korea
| | - G R Stewart
- Physics Department, University of Florida, Gainesville, FL 32611-8440, United States of America
| |
Collapse
|
12
|
Podsiadły-Paszkowska A, Krawiec M. Rehybridization-induced charge density oscillations in the long-range corrugated silicene. Phys Chem Chem Phys 2017; 19:14269-14275. [DOI: 10.1039/c7cp02352a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
One-dimensional long-range periodic structural deformation leads to a novel state of matter, called the rehybridization-induced sublattice-polarized charge density oscillation phase.
Collapse
Affiliation(s)
| | - Mariusz Krawiec
- Institute of Physics
- Maria Curie-Skłodowska University
- 20-031 Lublin
- Poland
| |
Collapse
|
13
|
Mou D, Kong T, Meier WR, Lochner F, Wang LL, Lin Q, Wu Y, Bud'ko SL, Eremin I, Johnson DD, Canfield PC, Kaminski A. Enhancement of the Superconducting Gap by Nesting in CaKFe_{4}As_{4}: A New High Temperature Superconductor. PHYSICAL REVIEW LETTERS 2016; 117:277001. [PMID: 28084772 DOI: 10.1103/physrevlett.117.277001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Indexed: 06/06/2023]
Abstract
We use high resolution angle resolved photoemission spectroscopy and density functional theory with measured crystal structure parameters to study the electronic properties of CaKFe_{4}As_{4}. In contrast to the related CaFe_{2}As_{2} compounds, CaKFe_{4}As_{4} has a high T_{c} of 35 K at stochiometric composition. This presents a unique opportunity to study the properties of high temperature superconductivity in the iron arsenides in the absence of doping or substitution. The Fermi surface consists of several hole and electron pockets that have a range of diameters. We find that the values of the superconducting gap are nearly isotropic (within the explored portions of the Brillouin zone), but are significantly different for each of the Fermi surface (FS) sheets. Most importantly, we find that the momentum dependence of the gap magnitude plotted across the entire Brillouin zone displays a strong deviation from the simple cos(k_{x})cos(k_{y}) functional form of the gap function, proposed by the scenario of Cooper pairing driven by a short range antiferromagnetic exchange interaction. Instead, the maximum value of the gap is observed on FS sheets that are closest to the ideal nesting condition, in contrast to previous observations in other ferropnictides. These results provide strong support for the multiband character of superconductivity in CaKFe_{4}As_{4}, in which Cooper pairing forms on the electron and the hole bands interacting via a dominant interband repulsive interaction, enhanced by band nesting.
Collapse
Affiliation(s)
- Daixiang Mou
- Division of Materials Science and Engineering, Ames Laboratory, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Tai Kong
- Division of Materials Science and Engineering, Ames Laboratory, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - William R Meier
- Division of Materials Science and Engineering, Ames Laboratory, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Felix Lochner
- Institut fur Theoretische Physik III, Ruhr-Universitat Bochum, 44801 Bochum, Germany
| | - Lin-Lin Wang
- Division of Materials Science and Engineering, Ames Laboratory, Ames, Iowa 50011, USA
| | - Qisheng Lin
- Division of Materials Science and Engineering, Ames Laboratory, Ames, Iowa 50011, USA
| | - Yun Wu
- Division of Materials Science and Engineering, Ames Laboratory, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - S L Bud'ko
- Division of Materials Science and Engineering, Ames Laboratory, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Ilya Eremin
- Institut fur Theoretische Physik III, Ruhr-Universitat Bochum, 44801 Bochum, Germany
| | - D D Johnson
- Division of Materials Science and Engineering, Ames Laboratory, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
- Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011, USA
| | - P C Canfield
- Division of Materials Science and Engineering, Ames Laboratory, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Adam Kaminski
- Division of Materials Science and Engineering, Ames Laboratory, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| |
Collapse
|
14
|
Yu R, Nevidomskyy AH. Competing superconducting channels in iron pnictides from the strong coupling theory with biquadratic spin interactions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:495702. [PMID: 27736803 DOI: 10.1088/0953-8984/28/49/495702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We study the symmetry and strength of the superconducting pairing in a two-orbital [Formula: see text] model for iron pnictides using the slave boson strong coupling approach. We show that the nearest-neighbor biquadratic interaction [Formula: see text] strongly affects the superconducting pairing phase diagram by promoting the [Formula: see text] B 1g and the [Formula: see text] A 1g channels. The resulting phase diagram consists of several competing pairing channels, including the isotropic [Formula: see text] A 1g channel, an anisotropic [Formula: see text] B 1g channel, and two [Formula: see text] pairing channels. We have investigated the evolution of superconducting states with electron doping, and find that the biquadratic interaction plays a crucial role in stabilizing the [Formula: see text] and even pure d-wave pairing in the heavily electron- and hole-doped regimes. In addition, we identify a novel orbital-B 1g pairing channel, which has a s-wave form factor but a B 1g symmetry. This channel has a comparable pairing amplitude to the d-wave pairing, and may strongly influence the superconducting gap anisotropy of the system in the overdoped regime. These findings are crucial in understanding the doping evolution of the superconducting gap anisotropy observed by angle resolved photoemission spectroscopy in the iron pnictides and iron chalcogenides, including the heavily K-doped BaFe2As2 and K-doped FeSe films.
Collapse
Affiliation(s)
- Rong Yu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, People's Republic of China. Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China and Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
| | | |
Collapse
|
15
|
Nourafkan R, Kotliar G, Tremblay AMS. Correlation-Enhanced Odd-Parity Interorbital Singlet Pairing in the Iron-Pnictide Superconductor LiFeAs. PHYSICAL REVIEW LETTERS 2016; 117:137001. [PMID: 27715100 DOI: 10.1103/physrevlett.117.137001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Indexed: 06/06/2023]
Abstract
The rich variety of iron-based superconductors and their complex electronic structure lead to a wide range of possibilities for gap symmetry and pairing components. Here we solve in the two-Fe Brillouin zone the full frequency-dependent linearized Eliashberg equations to investigate spin-fluctuations mediated Cooper pairing for LiFeAs. The magnetic excitations are calculated with the random phase approximation on a correlated electronic structure obtained with density functional theory and dynamical mean field theory. The interaction between electrons through Hund's coupling promotes both the intraorbital d_{xz(yz)} and the interorbital magnetic susceptibility. As a consequence, the leading pairing channel, conventional s^{+-}, acquires sizable interorbital d_{xy}-d_{xz(yz)} singlet pairing with odd parity under glide-plane symmetry. The combination of intra- and interorbital components makes the results consistent with available experiments on the angular dependence of the gaps observed on the different Fermi surfaces.
Collapse
Affiliation(s)
- R Nourafkan
- Département de Physique and Institut quantique, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
| | - G Kotliar
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854-8019, USA
| | - A-M S Tremblay
- Département de Physique and Institut quantique, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
- Quantum Materials Program, Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada
| |
Collapse
|
16
|
Zhang Y, Lee JJ, Moore RG, Li W, Yi M, Hashimoto M, Lu DH, Devereaux TP, Lee DH, Shen ZX. Superconducting Gap Anisotropy in Monolayer FeSe Thin Film. PHYSICAL REVIEW LETTERS 2016; 117:117001. [PMID: 27661715 DOI: 10.1103/physrevlett.117.117001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Indexed: 06/06/2023]
Abstract
Superconductivity originates from pairing of electrons near the Fermi energy. The Fermi surface topology and pairing symmetry are thus two pivotal characteristics of a superconductor. Superconductivity in one monolayer (1 ML) FeSe thin film has attracted great interest recently due to its intriguing interfacial properties and possibly high superconducting transition temperature over 65 K. Here, we report high-resolution measurements of the Fermi surface and superconducting gaps in 1 ML FeSe using angle-resolved photoemission spectroscopy. Two ellipselike electron pockets are clearly resolved overlapping with each other at the Brillouin zone corner. The superconducting gap is nodeless but moderately anisotropic, which puts strong constraint on determining the pairing symmetry. The gap maxima locate on the d_{xy} bands along the major axis of the ellipse and four gap minima are observed at the intersections of electron pockets. The gap maximum location combined with the Fermi surface geometry deviate from a single d-wave, extended s-wave or s_{±} gap function, suggesting an important role of the multiorbital nature of Fermi surface and orbital-dependent pairing in 1 ML FeSe. The gap minima location may be explained by a sign change on the electron pockets, or a competition between intra- and interorbital pairing.
Collapse
Affiliation(s)
- Y Zhang
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - J J Lee
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
| | - R G Moore
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - W Li
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - M Yi
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
| | - M Hashimoto
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - D H Lu
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - T P Devereaux
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
| | - D-H Lee
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
- Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Z-X Shen
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
| |
Collapse
|
17
|
Hong J, Abergel DSL. A universal explanation of tunneling conductance in exotic superconductors. Sci Rep 2016; 6:31352. [PMID: 27511315 PMCID: PMC4980671 DOI: 10.1038/srep31352] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 07/12/2016] [Indexed: 11/30/2022] Open
Abstract
A longstanding mystery in understanding cuprate superconductors is the inconsistency between the experimental data measured by scanning tunneling spectroscopy (STS) and angle-resolved photoemission spectroscopy (ARPES). In particular, the gap between prominent side peaks observed in STS is much bigger than the superconducting gap observed by ARPES measurements. Here, we reconcile the two experimental techniques by generalising a theory which was previously applied to zero-dimensional mesoscopic Kondo systems to strongly correlated two-dimensional (2D) exotic superconductors. We show that the side peaks observed in tunneling conductance measurements in all these materials have a universal origin: They are formed by coherence-mediated tunneling under bias and do not directly reflect the underlying density of states (DOS) of the sample. We obtain theoretical predictions of the tunneling conductance and the density of states of the sample simultaneously and show that for cuprate and pnictide superconductors, the extracted sample DOS is consistent with the superconducting gap measured by ARPES.
Collapse
Affiliation(s)
- Jongbae Hong
- Center for Theoretical Physics of Complex Systems, Institute for Basic Science, Daejeon 305-811, Korea
| | - D S L Abergel
- Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden.,Center for Quantum Materials, KTH and Nordita, Roslagstullsbacken 11, SE-106 91 Stockholm, Sweden
| |
Collapse
|
18
|
Abstract
A non-trivial temperature evolution of superconductivity including a temperature-induced phase transition between two superconducting phases or even a time-reversal symmetry breaking order parameter is in principle expected in multiband superconductors such as iron-pnictides. Here we present scanning tunnelling spectroscopy data of LiFeAs which reveal two distinct superconducting phases: at = 18 K a partial superconducting gap opens, evidenced by subtle, yet clear features in the tunnelling spectra, i.e. particle-hole symmetric coherence peak and dip-hump structures. At Tc = 16 K, these features substantiate dramatically and become characteristic of full superconductivity. Remarkably, the distance between the dip-hump structures and the coherence peaks remains practically constant in the whole temperature regimeT ≤ . This rules out the connection of the dip-hump structures to an antiferromagnetic spin resonance.
Collapse
|
19
|
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.
Collapse
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
| | | | | |
Collapse
|
20
|
Hwang J, Carbotte JP, Min BH, Kwon YS, Timusk T. Electron-boson spectral density of LiFeAs obtained from optical data. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:055701. [PMID: 25612554 DOI: 10.1088/0953-8984/27/5/055701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We analyze existing optical data in the superconducting state of LiFeAs at T = 4 K, to recover its electron-boson spectral density. A maximum entropy technique is employed to extract the spectral density I(2)χ(ω) from the optical scattering rate. Care is taken to properly account for elastic impurity scattering which can importantly affect the optics in an s-wave superconductor, but does not eliminate the boson structure. We find a robust peak in I(2)χ(ω) centered about Ω(R) ≅ 8.0 meV or 5.3 k(B)Tc (with Tc = 17.6 K). Its position in energy agrees well with a similar structure seen in scanning tunneling spectroscopy (STS). There is also a peak in the inelastic neutron scattering (INS) data at this same energy. This peak is found to persist in the normal state at T = 23 K. There is evidence that the superconducting gap is anisotropic as was also found in low temperature angular resolved photoemission (ARPES) data.
Collapse
Affiliation(s)
- J Hwang
- Department of Physics, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746, Republic of Korea
| | | | | | | | | |
Collapse
|
21
|
Miao H, Qian T, Shi X, Richard P, Kim TK, Hoesch M, Xing LY, Wang XC, Jin CQ, Hu JP, Ding H. Observation of strong electron pairing on bands without Fermi surfaces in LiFe1−xCoxAs. Nat Commun 2015; 6:6056. [PMID: 25583450 DOI: 10.1038/ncomms7056] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2014] [Accepted: 12/09/2014] [Indexed: 11/10/2022] Open
|
22
|
Xing LY, Miao H, Wang XC, Ma J, Liu QQ, Deng Z, Ding H, Jin CQ. The anomaly Cu doping effects on LiFeAs superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:435703. [PMID: 25299428 DOI: 10.1088/0953-8984/26/43/435703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The Cu substitution effect on the superconductivity of LiFeAs has been studied in comparison with Co/Ni substitution. It is found that the shrinking rate of the lattice parameter c for Cu substitution is much smaller than that of Co/Ni substitution. This is in conjugation with the observation of ARPES that shows almost the same electron and hole Fermi surfaces (FSs) size for undoped and Cu substituted LiFeAs sample, except for a very small hole band sinking below Fermi level with doping. This indicates that there is little doping effect at Fermi surface by Cu substitution, in sharp contrast to the more effective carrier doping effect by Ni or Co.
Collapse
Affiliation(s)
- L Y Xing
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | | | | | | | | | | | | | | |
Collapse
|
23
|
Chen X, Dai P, Feng D, Xiang T, Zhang FC. Iron-based high transition temperature superconductors. Natl Sci Rev 2014. [DOI: 10.1093/nsr/nwu007] [Citation(s) in RCA: 148] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
In a superconductor electrons form pairs and electric transport becomes dissipation-less at low temperatures. Recently discovered iron-based superconductors have the highest superconducting transition temperature next to copper oxides. In this article, we review material aspects and physical properties of iron-based superconductors. We discuss the dependence of transition temperature on the crystal structure, the interplay between antiferromagnetism and superconductivity by examining neutron scattering experiments, and the electronic properties of these compounds obtained by angle-resolved photoemission spectroscopy in link with some results from scanning tunneling microscopy/spectroscopy measurements. Possible microscopic model for this class of compounds is discussed from a strong coupling point of view.
Collapse
Affiliation(s)
- Xianhui Chen
- Department of Physics, University of Science and Technology of China, Hefei, 230026, China
| | - Pengcheng Dai
- Department of Physics and Astronomy, Rice University, Houston, TX 77005, USA
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Donglai Feng
- Department of Physics, Fudan University, Shanghai 200433, China
| | - Tao Xiang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
| | - Fu-Chun Zhang
- Department of Physics, Zhejiang University, Hangzhou, 310027, China
| |
Collapse
|
24
|
Peng R, Shen XP, Xie X, Xu HC, Tan SY, Xia M, Zhang T, Cao HY, Gong XG, Hu JP, Xie BP, Feng DL. Measurement of an enhanced superconducting phase and a pronounced anisotropy of the energy gap of a strained FeSe single layer in FeSe/Nb:SrTiO3/KTaO3 heterostructures using photoemission spectroscopy. PHYSICAL REVIEW LETTERS 2014; 112:107001. [PMID: 24679321 DOI: 10.1103/physrevlett.112.107001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Indexed: 06/03/2023]
Abstract
Single-layer FeSe films with an extremely expanded in-plane lattice constant of 3.99±0.02 Å are fabricated by epitaxially growing FeSe/Nb:SrTiO3/KTaO3 heterostructures and studied by in situ angle-resolved photoemission spectroscopy. Two elliptical electron pockets at the Brillouin zone corner are resolved with negligible hybridization between them, indicating that the symmetry of the low-energy electronic structure remains intact as a freestanding single-layer FeSe, although it is on a substrate. The superconducting gap closes at a record high temperature of 70 K for the iron-based superconductors. Intriguingly, the superconducting gap distribution is anisotropic but nodeless around the electron pockets, with minima at the crossings of the two pockets. Our results place strong constraints on current theories.
Collapse
Affiliation(s)
- R Peng
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China
| | - X P Shen
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China
| | - X Xie
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China
| | - H C Xu
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China
| | - S Y Tan
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China
| | - M Xia
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China
| | - T Zhang
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China
| | - H Y Cao
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Key Laboratory for Computational Physical Sciences (MOE), Fudan University, Shanghai 200433, China
| | - X G Gong
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Key Laboratory for Computational Physical Sciences (MOE), Fudan University, Shanghai 200433, China
| | - J P Hu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People's Republic of China and Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA
| | - B P Xie
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China
| | - D L Feng
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China
| |
Collapse
|
25
|
Ummarino GA, Galasso S, Sanna A. A phenomenological multiband Eliashberg model for LiFeAs. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:205701. [PMID: 23614978 DOI: 10.1088/0953-8984/25/20/205701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The phenomenology of a LiFeAs superconductor can be explained in the framework of four-band s±-wave Eliashberg theory. We have examined the experimental data available in the literature and we have found that it is possible to reproduce the experimental critical temperature, the gap values and the upper critical magnetic field within an effective model in a moderately strong coupling regime that must include both an intraband term λ11 ∼ 0.9 and an interband spin-fluctuation ([Formula: see text]) coupling. The presence of a nonnegligible intraband coupling can be a fictitious effect of the violation of Migdal's theorem.
Collapse
Affiliation(s)
- G A Ummarino
- Istituto di Ingegneria e Fisica dei Materiali, Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, Corso Duca degli Abruzzi 24, I-10129 Torino, Italy.
| | | | | |
Collapse
|
26
|
Hess C, Sykora S, Hänke T, Schlegel R, Baumann D, Zabolotnyy VB, Harnagea L, Wurmehl S, van den Brink J, Büchner B. Interband quasiparticle scattering in superconducting LiFeAs reconciles photoemission and tunneling measurements. PHYSICAL REVIEW LETTERS 2013; 110:017006. [PMID: 23383831 DOI: 10.1103/physrevlett.110.017006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Indexed: 06/01/2023]
Abstract
Several angle-resolved photoemission spectroscopy (ARPES) studies reveal a poorly nested Fermi surface of LiFeAs, far away from a spin density wave instability, and clear-cut superconducting gap anisotropies. On the other hand a very different, more nested Fermi surface and dissimilar gap anisotropies have been obtained from quasiparticle interference (QPI) data, which were interpreted as arising from intraband scattering within holelike bands. Here we show that this ARPES-QPI paradox is completely resolved by interband scattering between the holelike bands. The resolution follows from an excellent agreement between experimental quasiparticle scattering data and T-matrix QPI calculations (based on experimental band structure data), which allows disentangling interband and intraband scattering processes.
Collapse
|
27
|
Kim JS, Stewart GR, Xing LY, Wang XC, Jin CQ. Specific heat versus field for LiFe(1-x)Cu(x)As. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:475701. [PMID: 23103601 DOI: 10.1088/0953-8984/24/47/475701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
LiFeAs is one of the new class of iron superconductors with a bulk [Formula: see text] in the 15-17 K range. We report on the specific heat characterization of single crystal material prepared by self-flux growth techniques with significantly improved properties, including a much decreased residual gamma, γ(r) (≡C/T as T → 0), in the superconducting state. Thus, in contrast to previous explanations of a finite γ(r) in LiFeAs being due to intrinsic states in the superconducting gap, the present work shows that such a finite residual γ in LiFeAs is instead a function of sample quality. Further, since LiFeAs has been characterized as nodeless with multiple superconducting gaps, we report here on its specific heat properties in zero and applied magnetic fields, to compare to similar results on nodal iron superconductors. For comparison, we also investigate LiFe(0.98)Cu(0.02)As, which has the reduced T(c) of ≈9 K and an H(c2) of 15 T. Interestingly, although presumably both LiFeAs and LiFe(0.98)Cu(0.02)As are nodeless, they clearly show a non-linear dependence of the electronic density of states (is proportional to specific heat γ) at the Fermi energy in the mixed state with the applied field, similar to the Volovik effect for nodal superconductors. However, rather than indicating nodal behavior, the satisfactory comparison with a recent theory for γ(H) for a superconductor with two isotropic gaps in the presence of impurities argues for nodeless behavior. Thus, in terms of specific heat in a magnetic field, LiFeAs can serve as the prototypical multiband, nodeless iron superconductor.
Collapse
Affiliation(s)
- J S Kim
- Department of Physics, University of Florida, Gainesville, FL 32611-8440, USA
| | | | | | | | | |
Collapse
|
28
|
Rullier-Albenque F, Colson D, Forget A, Alloul H. Multiorbital effects on the transport and the superconducting fluctuations in LiFeAs. PHYSICAL REVIEW LETTERS 2012; 109:187005. [PMID: 23215320 DOI: 10.1103/physrevlett.109.187005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Indexed: 06/01/2023]
Abstract
The resistivity, Hall effect, and transverse magnetoresistance have been measured in low residual resistivity single crystals of LiFeAs. A comparison with angle resolved photoemission spectroscopy and quantum oscillation data implies that four carrier bands unevenly contribute to the transport. However the scattering rates of the carriers all display the T(2) behavior expected for a Fermi liquid. Near T(c) low field deviations of the magnetoresistance with respect to a H(2) variation permit us to extract the superconducting fluctuation contribution to the conductivity. Though below T(c) the anisotropy of superconductivity is rather small, the superconducting fluctuation displays a quasi-ideal two-dimensional behavior which persists up to 1.4 T(c). These results call for a refined theoretical understanding of the multiband behavior of superconductivity in this pnictide.
Collapse
Affiliation(s)
- F Rullier-Albenque
- Service de Physique de l'Etat Condensé, Orme des Merisiers, CEA Saclay, CNRS URA 2464, 91191 Gif sur Yvette cedex, France.
| | | | | | | |
Collapse
|
29
|
Lee G, Ji HS, Kim Y, Kim C, Haule K, Kotliar G, Lee B, Khim S, Kim KH, Kim KS, Kim KS, Shim JH. Orbital selective Fermi surface shifts and mechanism of high T(c) superconductivity in correlated AFeAs (A=Li, Na). PHYSICAL REVIEW LETTERS 2012; 109:177001. [PMID: 23215215 DOI: 10.1103/physrevlett.109.177001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Indexed: 06/01/2023]
Abstract
Based on the dynamical mean field theory and angle resolved photoemission spectroscopy, we have investigated the mechanism of high T(c) superconductivity in stoichiometric LiFeAs. The calculated spectrum is in excellent agreement with the measured angle resolved photoemission spectroscopy. The Fermi surface (FS) nesting, which is predicted in the conventional density functional theory method, is suppressed due to the orbital-dependent correlation effect within the dynamical mean field theory method. We have shown that such marginal breakdown of the FS nesting is an essential condition to the spin-fluctuation mediated superconductivity, while the good FS nesting in NaFeAs induces a spin density wave ground state. Our results indicate that a fully charge self-consistent description of the correlation effect is crucial in the description of the FS nesting-driven instabilities.
Collapse
Affiliation(s)
- Geunsik Lee
- Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Chi S, Grothe S, Liang R, Dosanjh P, Hardy WN, Burke SA, Bonn DA, Pennec Y. Scanning tunneling spectroscopy of superconducting LiFeAs single crystals: evidence for two nodeless energy gaps and coupling to a bosonic mode. PHYSICAL REVIEW LETTERS 2012; 109:087002. [PMID: 23002767 DOI: 10.1103/physrevlett.109.087002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Indexed: 06/01/2023]
Abstract
The superconducting compound LiFeAs is studied by scanning tunneling microscopy and spectroscopy. A gap map of the unreconstructed surface indicates a high degree of homogeneity in this system. Spectra at 2 K show two nodeless superconducting gaps with Δ(1)=5.3±0.1 meV and Δ(2)=2.5±0.2 meV. The gaps close as the temperature is increased to the bulk T(c), indicating that the surface accurately represents the bulk. A dip-hump structure is observed below T(c) with an energy scale consistent with a magnetic resonance recently reported by inelastic neutron scattering.
Collapse
Affiliation(s)
- Shun Chi
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada
| | | | | | | | | | | | | | | |
Collapse
|
31
|
Allan MP, Rost AW, Mackenzie AP, Xie Y, Davis JC, Kihou K, Lee CH, Iyo A, Eisaki H, Chuang TM. Anisotropic Energy Gaps of Iron-Based Superconductivity from Intraband Quasiparticle Interference in LiFeAs. Science 2012; 336:563-7. [DOI: 10.1126/science.1218726] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- M. P. Allan
- Condensed Matter Physics and Materials Science (CMPMS) Department, Brookhaven National Laboratory, Upton, NY 11973, USA
- Laboratory of Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA
- Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - A. W. Rost
- Laboratory of Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA
- Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - A. P. Mackenzie
- Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - Yang Xie
- Laboratory of Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA
| | - J. C. Davis
- Condensed Matter Physics and Materials Science (CMPMS) Department, Brookhaven National Laboratory, Upton, NY 11973, USA
- Laboratory of Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA
- Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA
| | - K. Kihou
- Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
- Japan Science and Technology Agency (JST), Transformative Research-Project on Iron Pnictides (TRIP), Tokyo 102-0075, Japan
| | - C. H. Lee
- Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
- Japan Science and Technology Agency (JST), Transformative Research-Project on Iron Pnictides (TRIP), Tokyo 102-0075, Japan
| | - A. Iyo
- Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
- Japan Science and Technology Agency (JST), Transformative Research-Project on Iron Pnictides (TRIP), Tokyo 102-0075, Japan
| | - H. Eisaki
- Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
- Japan Science and Technology Agency (JST), Transformative Research-Project on Iron Pnictides (TRIP), Tokyo 102-0075, Japan
| | - T.-M. Chuang
- Condensed Matter Physics and Materials Science (CMPMS) Department, Brookhaven National Laboratory, Upton, NY 11973, USA
- Laboratory of Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853, USA
- Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan
| |
Collapse
|