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Li C, Song Y, Wang X, Lei M, Chen X, Xu H, Peng R, Feng D. Interface-Suppressed Nematicity and Enhanced Superconducting Pairing Strength of FeSe/NdFeO 3 in the Low-Doping Regime. NANO LETTERS 2024. [PMID: 38934420 DOI: 10.1021/acs.nanolett.4c01493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/28/2024]
Abstract
The discovery of interfacial superconductivity in monolayer FeSe/oxides has spurred intensive research interest. Here we not only extend the FeSe/FeOx superconducting interface to FeSe/NdFeO3 but also establish robust interface-enhanced superconductivity at a very low doping level. Specifically, well-annealed FeSe/NdFeO3 exhibits a low doping level of 0.038-0.046 e-/Fe with a larger superconducting pairing gap without a nematic gap, indicating an enhancement of the enhanced superconducting pairing strength and suppression of nematicity by the FeSe/FeOx interface compared with those of thick FeSe films. These results improve our understanding of the roles of the oxide interface in the low-electron-doped regime.
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Affiliation(s)
- Chihao Li
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200438, China
| | - Yuanhe Song
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200438, China
| | - Xiaoxiao Wang
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200438, China
| | - Minyinan Lei
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200438, China
| | - Xiaoyang Chen
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200438, China
| | - Haichao Xu
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200438, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Rui Peng
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200438, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Donglai Feng
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200438, China
- National Synchrotron Radiation Laboratory and School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026, China
- New Cornerstone Science Laboratory, University of Science and Technology of China, Hefei 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
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2
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Jiao X, Dong W, Shi M, Wang H, Ding C, Wei Z, Gong G, Li Y, Li Y, Zuo B, Wang J, Zhang D, Pan M, Wang L, Xue QK. Significantly enhanced superconductivity in monolayer FeSe films on SrTiO 3(001) via metallic δ-doping. Natl Sci Rev 2024; 11:nwad213. [PMID: 38312379 PMCID: PMC10833465 DOI: 10.1093/nsr/nwad213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 07/19/2023] [Accepted: 07/25/2023] [Indexed: 02/06/2024] Open
Abstract
Superconductivity transition temperature (Tc) marks the inception of a macroscopic quantum phase-coherent paired state in fermionic systems. For 2D superconductivity, the paired electrons condense into a coherent superfluid state at Tc, which is usually lower than the pairing temperature, between which intrinsic physics including Berezinskii-Kosterlitz-Thouless transition and pseudogap state are hotly debated. In the case of monolayer FeSe superconducting films on SrTiO3(001), although the pairing temperature (Tp) is revealed to be 65-83 K by using spectroscopy characterization, the measured zero-resistance temperature ([Formula: see text]) is limited to 20 K. Here, we report significantly enhanced superconductivity in monolayer FeSe films by δ-doping of Eu or Al on SrTiO3(001) surface, in which [Formula: see text] is enhanced by 12 K with a narrowed transition width ΔTc ∼ 8 K, compared with non-doped samples. Using scanning tunneling microscopy/spectroscopy measurements, we demonstrate lowered work function of the δ-doped SrTiO3(001) surface and enlarged superconducting gaps in the monolayer FeSe with improved morphology/electronic homogeneity. Our work provides a practical route to enhance 2D superconductivity by using interface engineering.
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Affiliation(s)
- Xiaotong Jiao
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- School of Physics & Information Technology, Shaanxi Normal University, Xi'an 710119, China
| | - Wenfeng Dong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Mingxia Shi
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Heng Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Cui Ding
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Zhongxu Wei
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Guanming Gong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Yanan Li
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA
| | - Yuanzhao Li
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Binjie Zuo
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Jian Wang
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
- Hefei National Laboratory, Hefei 230088, China
| | - Ding Zhang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Minghu Pan
- School of Physics & Information Technology, Shaanxi Normal University, Xi'an 710119, China
| | - Lili Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
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Zakeri K, Rau D, Jandke J, Yang F, Wulfhekel W, Berthod C. Direct Probing of a Large Spin-Orbit Coupling in the FeSe Superconducting Monolayer on STO. ACS NANO 2023; 17:9575-9585. [PMID: 37155694 DOI: 10.1021/acsnano.3c02876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Spin-orbit coupling (SOC) is a fundamental physical interaction, which describes how the electrons' spin couples to their orbital motion. It is the source of a vast variety of fascinating phenomena in nanostructures. Although in most theoretical descriptions of high-temperature superconductivity SOC has been neglected, including this interaction can, in principle, revise the microscopic picture. Here by preforming energy-, momentum-, and spin-resolved spectroscopy experiments we demonstrate that while probing the dynamic charge response of the FeSe monolayer on strontium titanate, a prototype two-dimensional high-temperature superconductor using electrons, the scattering cross-section is spin dependent. We unravel the origin of the observed phenomenon and show that SOC in this two-dimensional superconductor is strong. We anticipate that such a strong SOC can have several consequences on the electronic structures and may compete with other pairing scenarios and be crucial for the mechanism of superconductivity.
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Affiliation(s)
- Khalil Zakeri
- Heisenberg Spin-dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Straße 1, D-76131 Karlsruhe, Germany
| | - Dominik Rau
- Heisenberg Spin-dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Straße 1, D-76131 Karlsruhe, Germany
| | - Jasmin Jandke
- Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Straße 1, D-76131 Karlsruhe, Germany
| | - Fang Yang
- Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Straße 1, D-76131 Karlsruhe, Germany
| | - Wulf Wulfhekel
- Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Straße 1, D-76131 Karlsruhe, Germany
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, D-76344, Eggenstein-Leopoldshafen, Germany
| | - Christophe Berthod
- Department of Quantum Matter Physics, University of Geneva, 1211 Geneva, Switzerland
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Stoichiometric Growth of Monolayer FeSe Superconducting Films Using a Selenium Cracking Source. CRYSTALS 2022. [DOI: 10.3390/cryst12060853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
As a novel interfacial high-temperature superconductor, monolayer FeSe on SrTiO3 has been intensely studied in the past decade. The high selenium flux involved in the traditional growth method complicates the film’s composition and entails more sample processing to realize the superconductivity. Here we use a Se cracking source for the molecular beam epitaxy growth of FeSe films to boost the reactivity of the Se flux. Reflection high-energy electron diffraction shows that the growth rate of FeSe increases with the increasing Se flux when the Fe flux is fixed, indicating that the Se over-flux induces Fe vacancies. Through careful tuning, we find that the proper Se/Fe flux ratio with Se cracked that is required for growing stoichiometric FeSe is close to 1, much lower than that with the uncracked Se flux. Furthermore, the FeSe film produced by the optimized conditions shows high-temperature superconductivity in the transport measurements without any post-growth treatment. Our work reinforces the importance of stoichiometry for superconductivity and establishes a simpler and more efficient approach to fabricating monolayer FeSe superconducting films.
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Song Y, Chen Z, Zhang Q, Xu H, Lou X, Chen X, Xu X, Zhu X, Tao R, Yu T, Ru H, Wang Y, Zhang T, Guo J, Gu L, Xie Y, Peng R, Feng D. High temperature superconductivity at FeSe/LaFeO 3 interface. Nat Commun 2021; 12:5926. [PMID: 34635672 PMCID: PMC8505662 DOI: 10.1038/s41467-021-26201-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 09/15/2021] [Indexed: 11/09/2022] Open
Abstract
Enormous enhancement of superconducting pairing temperature (Tg) to 65 K in FeSe/SrTiO3 has made it a spotlight. Despite the effort of interfacial engineering, FeSe interfaced with TiOx remains the unique case in hosting high Tg, hindering a decisive understanding on the general mechanism and ways to further improving Tg. Here we constructed a new high-Tg interface, single-layer FeSe interfaced with FeOx-terminated LaFeO3. Large superconducting gap and diamagnetic response evidence that the superconducting pairing can emerge near 80 K, highest amongst all-known interfacial superconductors. Combining various techniques, we reveal interfacial charge transfer and strong interfacial electron-phonon coupling (EPC) in FeSe/LaFeO3, showing that the cooperative pairing mechanism works beyond FeSe-TiOx. Intriguingly, the stronger interfacial EPC than that in FeSe/SrTiO3 is likely induced by the stronger interfacial bonding in FeSe/LaFeO3, and can explain the higher Tg according to recent theoretical calculations, pointing out a workable route in designing new interfaces to achieve higher Tg.
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Affiliation(s)
- Yuanhe Song
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Zheng Chen
- Department of Physics, Zhejiang University, 310027, Hangzhou, China
| | - Qinghua Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Haichao Xu
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
- Shanghai Research Center for Quantum Sciences, 201315, Shanghai, China
| | - Xia Lou
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Xiaoyang Chen
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Xiaofeng Xu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Xuetao Zhu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Ran Tao
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Tianlun Yu
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Hao Ru
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
| | - Yihua Wang
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
- Shanghai Research Center for Quantum Sciences, 201315, Shanghai, China
| | - Tong Zhang
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China
- Shanghai Research Center for Quantum Sciences, 201315, Shanghai, China
| | - Jiandong Guo
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.
| | - Lin Gu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.
| | - Yanwu Xie
- Department of Physics, Zhejiang University, 310027, Hangzhou, China.
| | - Rui Peng
- Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 200438, Shanghai, China.
- Shanghai Research Center for Quantum Sciences, 201315, Shanghai, China.
| | - Donglai Feng
- Shanghai Research Center for Quantum Sciences, 201315, Shanghai, China.
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, 230026, Hefei, Anhui, China.
- Collaborative Innovation Center of Advanced Microstructures, 210093, Nanjing, China.
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6
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High-order replica bands in monolayer FeSe/SrTiO 3 revealed by polarization-dependent photoemission spectroscopy. Nat Commun 2021; 12:4573. [PMID: 34321473 PMCID: PMC8319137 DOI: 10.1038/s41467-021-24783-5] [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: 12/29/2020] [Accepted: 07/09/2021] [Indexed: 11/13/2022] Open
Abstract
The mechanism of the enhanced superconductivity in monolayer FeSe/SrTiO3 has been enthusiastically studied and debated over the past decade. One specific observation has been taken to be of central importance: the replica bands in the photoemission spectrum. Although suggestive of electron-phonon interaction in the material, the essence of these spectroscopic features remains highly controversial. In this work, we conduct angle-resolved photoemission spectroscopy measurements on monolayer FeSe/SrTiO3 using linearly polarized photons. This configuration enables unambiguous characterization of the valence electronic structure with a suppression of the spectral background. We consistently observe high-order replica bands derived from various Fe 3d bands, similar to those observed on bare SrTiO3. The intensity of the replica bands is unexpectedly high and different between dxy and dyz bands. Our results provide new insights on the electronic structure of this high-temperature superconductor and the physical origin of the photoemission replica bands. The origin of the photoemission replica bands in monolayer FeSe/SrTiO3 remains controversial. Here, the authors perform angle-resolved photoemission spectroscopy with polarized photon on FeSe/SrTiO3 and observe high-order replica bands with high intensity from various Fe 3d bands, suggesting a mixed mechanism.
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7
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Zhang H, Zou Q, Li L. Tomonaga-Luttinger Liquid in the Topological Edge Channel of Multilayer FeSe. NANO LETTERS 2021; 21:6253-6260. [PMID: 34255523 DOI: 10.1021/acs.nanolett.1c02069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A two-dimensional topological insulator exhibits helical edge states topologically protected against single-particle backscattering. Such protection breaks down, however, when electron-electron interactions are significant or when edge reconstruction occurs, leading to a suppressed density of states (DOS) at the Fermi level that follows universal scaling with temperature and energy, characteristic of Tomonaga-Luttinger liquid (TLL). Here, we grow multilayer FeSe on SrTiO3 by molecular beam epitaxy and observe robust edge states at both the {100}Se and the {110}Se steps using scanning tunneling microscopy/spectroscopy. We determine the DOS follows a power law, resulting in the Luttinger parameter K of 0.26 ± 0.02 and 0.43 ± 0.07 for the {100}Se and {110}Se edges, respectively. The smaller K for the {100}Se edge also indicates strong correlations, attributed to ferromagnetic ordering likely present due to checkerboard antiferromagnetic fluctuations in FeSe. These results demonstrate TLL in FeSe helical edge channels, providing an exciting model system for novel topological excitations arising from superconductivity and interacting helical edge states.
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Affiliation(s)
- Huimin Zhang
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Qiang Zou
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Lian Li
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, United States
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8
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Li Z, Sang L, Liu P, Yue Z, Fuhrer MS, Xue Q, Wang X. Atomically Thin Superconductors. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e1904788. [PMID: 32363776 DOI: 10.1002/smll.201904788] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Revised: 12/18/2019] [Accepted: 03/04/2020] [Indexed: 06/11/2023]
Abstract
In recent years, atomically thin superconductors, including atomically thin elemental superconductors, single layer FeSe films, and few-layer cuprate superconductors, have been studied extensively. This hot research field is mainly driven by the discovery of significant superconductivity enhancement and high-temperature interface superconductivity in single-layer FeSe films epitaxially grown on SrTiO3 substrates in 2012. This study has attracted tremendous research interest and generated more studies focusing on further enhancing superconductivity and finding the origin of the superconductivity. A few years later, research on atomically thin superconductors has extended to cuprate superconductors, unveiling many intriguing properties that have neither been proposed or observed previously. These new discoveries challenge the current theory regarding the superconducting mechanism of unconventional superconductors and indicate new directions on how to achieve high-transition-temperature superconductors. Herein, this exciting recent progress is briefly discussed, with a focus on the recent progress in identifying new atomically thin superconductors.
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Affiliation(s)
- Zhi Li
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), University of Wollongong, Wollongong, NSW, 2525, Australia
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW, 2525, Australia
| | - Lina Sang
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), University of Wollongong, Wollongong, NSW, 2525, Australia
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW, 2525, Australia
| | - Peng Liu
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), University of Wollongong, Wollongong, NSW, 2525, Australia
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW, 2525, Australia
| | - Zengji Yue
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), University of Wollongong, Wollongong, NSW, 2525, Australia
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW, 2525, Australia
| | - Michael S Fuhrer
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), Monash University, Victoria, 3800, Australia
| | - Qikun Xue
- Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Xiaolin Wang
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), University of Wollongong, Wollongong, NSW, 2525, Australia
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW, 2525, Australia
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9
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Kang BL, Shi MZ, Li SJ, Wang HH, Zhang Q, Zhao D, Li J, Song DW, Zheng LX, Nie LP, Wu T, Chen XH. Preformed Cooper Pairs in Layered FeSe-Based Superconductors. PHYSICAL REVIEW LETTERS 2020; 125:097003. [PMID: 32915588 DOI: 10.1103/physrevlett.125.097003] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 06/06/2020] [Accepted: 07/27/2020] [Indexed: 06/11/2023]
Abstract
Superconductivity arises from two distinct quantum phenomena: electron pairing and long-range phase coherence. In conventional superconductors, the two quantum phenomena generally take place simultaneously, while in the underdoped high- T_{c} cuprate superconductors, the electron pairing occurs at higher temperature than the long-range phase coherence. Recently, whether electron pairing is also prior to long-range phase coherence in single-layer FeSe film on SrTiO_{3} substrate is under debate. Here, by measuring Knight shift and nuclear spin-lattice relaxation rate, we unambiguously reveal a pseudogap behavior below T_{p}∼60 K in two kinds of layered FeSe-based superconductors with quasi2D nature. In the pseudogap regime, a weak diamagnetic signal and a remarkable Nernst effect are also observed, which indicates that the observed pseudogap behavior is related to superconducting fluctuations. These works confirm that strong phase fluctuation is an important character in the 2D iron-based superconductors as widely observed in high-T_{c} cuprate superconductors.
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Affiliation(s)
- B L Kang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - M Z Shi
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - S J Li
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - H H Wang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Q Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - D Zhao
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - J Li
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - D W Song
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - L X Zheng
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - L P Nie
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - T Wu
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence in Superconducting Electronics (CENSE), Shanghai 200050, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, Hefei, Anhui 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - X H Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Center for Excellence in Superconducting Electronics (CENSE), Shanghai 200050, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, Hefei, Anhui 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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10
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Ge Z, Zou Q, Zhang H, Yan C, Agterberg D, Weinert M, Li L. Superconductivity on Edge: Evidence of a One-Dimensional Superconducting Channel at the Edges of Single-Layer FeTeSe Antiferromagnetic Nanoribbons. ACS NANO 2020; 14:6539-6547. [PMID: 32363855 DOI: 10.1021/acsnano.9b08726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
How superconductivity emerges from antiferromagnetic ordering is an essential question for Fe-based superconductors. Here, we explore the effect of dimensionality on the interplay between antiferromagnetic ordering and superconductivity by investigating nanoribbons of single-layer FeTe1-xSex films grown on SrTiO3(001) substrates by molecular beam epitaxy. Using scanning tunneling microscopy/spectroscopy, we find a one-dimensional (1D) superconducting channel 2 nm wide with a TC of 42 ± 4 K on the edge of FeTe1-xSex (x < 0.1) ribbons, coexisting with a non-superconducting ribbon interior that remains bicollinear antiferromagnetically ordered. Density functional theory calculations indicate that both Se and the presence of the edge destabilize the bicollinear antiferromagnetic magnetic order, resulting in a paramagnetic region near the edge with strong local checkerboard fluctuations that is conducive to superconductivity. Our results represent the highest TC achieved in 1D superconductors and demonstrate an effective route toward stabilizing superconductivity in Fe-based superconductors at reduced dimensions.
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Affiliation(s)
- Zhuozhi Ge
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Qiang Zou
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Huimin Zhang
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Chenhui Yan
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Daniel Agterberg
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53211, United States
| | - Michael Weinert
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53211, United States
| | - Lian Li
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, United States
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11
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Peng R, Zou K, Han MG, Albright SD, Hong H, Lau C, Xu HC, Zhu Y, Walker FJ, Ahn CH. Picoscale structural insight into superconductivity of monolayer FeSe/SrTiO 3. SCIENCE ADVANCES 2020; 6:eaay4517. [PMID: 32284994 PMCID: PMC7141823 DOI: 10.1126/sciadv.aay4517] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 01/14/2020] [Indexed: 05/25/2023]
Abstract
Remarkable enhancement of the superconducting transition temperature (T c) has been observed for monolayer (ML) FeSe films grown on SrTiO3 substrates. The atomic-scale structure of the FeSe/SrTiO3 interface is an important determinant of both the magnetic and interfacial electron-phonon interactions and is a key ingredient to understanding its high-T c superconductivity. We resolve the atomic-scale structure of the FeSe/SrTiO3 interface through a complementary analysis of scanning transmission electron microscopy and in situ surface x-ray diffraction. We find that the interface is more strongly bonded for a particular registration, which leads to a coherently strained ML. We also determine structural parameters, such as the distance between ML FeSe and the oxide, Se─Fe─Se bond angles, layer-resolved distances between Fe─Se, and registry of the FeSe lattice relative to the oxide. This picoscale structure determination provides an explicit structural framework and constraint for theoretical approaches addressing the high-T c mechanism in FeSe/SrTiO3.
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Affiliation(s)
- Rui Peng
- Department of Applied Physics, Yale University, New Haven, CT 06520, USA
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520, USA
- Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China
| | - Ke Zou
- Department of Applied Physics, Yale University, New Haven, CT 06520, USA
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520, USA
| | - M. G. Han
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Stephen D. Albright
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520, USA
- Department of Physics, Yale University, New Haven, CT 06520, USA
| | - Hawoong Hong
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Claudia Lau
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520, USA
- Department of Physics, Yale University, New Haven, CT 06520, USA
| | - H. C. Xu
- Department of Applied Physics, Yale University, New Haven, CT 06520, USA
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520, USA
- Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China
| | - Yimei Zhu
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - F. J. Walker
- Department of Applied Physics, Yale University, New Haven, CT 06520, USA
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520, USA
| | - C. H. Ahn
- Department of Applied Physics, Yale University, New Haven, CT 06520, USA
- Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520, USA
- Department of Physics, Yale University, New Haven, CT 06520, USA
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06520, USA
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12
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Ge Z, Yan C, Zhang H, Agterberg D, Weinert M, Li L. Evidence for d-Wave Superconductivity in Single Layer FeSe/SrTiO 3 Probed by Quasiparticle Scattering Off Step Edges. NANO LETTERS 2019; 19:2497-2502. [PMID: 30916981 DOI: 10.1021/acs.nanolett.9b00135] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The de Gennes extrapolation length is a direction dependent measure of the spatial evolution of the pairing gap near the boundary of a superconductor and thus provides a viable means to probe its symmetry. It is expected to be infinite and isotropic for plain s-wave pairing, and finite and anisotropic for d-wave. Here, we synthesize single-layer FeSe films on SrTiO3(001) (STO) substrates by molecular beam epitaxy and measure the de Gennes extrapolation length by scanning tunneling microscopy/spectroscopy. We find a 40% reduction of the superconducting gap near specular [110]Fe edges, yielding an extrapolation length of 8.0 nm. However, near specular [010]Fe edges, the extrapolation length is nearly infinite. These findings are consistent with a phase changing pairing with 2-fold symmetry, indicating d-wave superconductivity. This is further supported by the presence of in-gap states near the specular [110]Fe edges, but not the [010]Fe edges. This work provides direct experimental evidence for d-wave superconductivity in single-layer FeSe/STO and demonstrates quasiparticle scattering at boundaries to be a viable phase sensitive probe of pairing symmetry in Fe-based superconductors.
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Affiliation(s)
- Zhuozhi Ge
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
- Department of Physics , University of Wisconsin , Milwaukee , Wisconsin 53211 , United States
| | - Chenhui Yan
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
| | - Huimin Zhang
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
| | - Daniel Agterberg
- Department of Physics , University of Wisconsin , Milwaukee , Wisconsin 53211 , United States
| | - Michael Weinert
- Department of Physics , University of Wisconsin , Milwaukee , Wisconsin 53211 , United States
| | - Lian Li
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26506 , United States
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13
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Evidence of cooperative effect on the enhanced superconducting transition temperature at the FeSe/SrTiO 3 interface. Nat Commun 2019; 10:758. [PMID: 30770805 PMCID: PMC6377624 DOI: 10.1038/s41467-019-08560-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 01/18/2019] [Indexed: 11/16/2022] Open
Abstract
At the interface between monolayer FeSe films and SrTiO3 substrates the superconducting transition temperature (Tc) is unexpectedly high, triggering a surge of excitement. The mechanism for the Tc enhancement has been the central question, as it may present a new strategy for seeking out higher Tc materials. To reveal this enigmatic mechanism, by combining advances in high quality interface growth, 16O \documentclass[12pt]{minimal}
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\begin{document}$$\leftrightarrow$$\end{document}↔18O isotope substitution, and extensive data from angle resolved photoemission spectroscopy, we provide striking evidence that the high Tc in FeSe/SrTiO3 is the cooperative effect of the intrinsic pairing mechanism in the FeSe and interactions between the FeSe electrons and SrTiO3 phonons. Furthermore, our results point to the promising prospect that similar cooperation between different Cooper pairing channels may be a general framework to understand and design high-temperature superconductors. The mechanism of enhanced superconducting transition temperature (Tc) at the FeSe/SrTiO3 interface remains enigmatic. Here, Song and Yu et al. reveal the evidence of cooperation between intrinsic pairing interaction in FeSe and interfacial electron–phonon coupling to enhance the Tc at the FeSe/SrTiO3 interface.
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14
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Gao Y, Wang Y, Zhou T, Huang H, Wang QH. Possible Pairing Symmetry in the FeSe-Based Superconductors Determined by Quasiparticle Interference. PHYSICAL REVIEW LETTERS 2018; 121:267005. [PMID: 30636135 DOI: 10.1103/physrevlett.121.267005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Indexed: 06/09/2023]
Abstract
We study the momentum-integrated quasiparticle interference (QPI) in the FeSe-based superconductors. This method was recently proposed theoretically and has been applied to determine the pairing symmetry in these materials experimentally. Our findings suggest that, if the incipient bands and the superconducting (SC) pairing on them are taken into consideration, then the experimentally measured bound states and momentum-integrated QPI can be well fitted, even if the SC order parameter does not change sign on the Fermi surfaces. Therefore, we offer an alternative explanation to the experimental data, calling for more careful identification of the pairing symmetry that is important for the pairing mechanism.
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Affiliation(s)
- Yi Gao
- Center for Quantum Transport and Thermal Energy Science, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China
- Jiangsu Key Lab on Opto-Electronic Technology, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China
| | - Yuting Wang
- Center for Quantum Transport and Thermal Energy Science, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China
| | - Tao Zhou
- Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, and School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006, China
| | - Huaixiang Huang
- Department of Physics, Shanghai University, Shanghai, 200444, China
| | - Qiang-Hua Wang
- National Laboratory of Solid State Microstructures & School of Physics, Nanjing University, Nanjing, 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
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15
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Zhao W, Li M, Chang CZ, Jiang J, Wu L, Liu C, Moodera JS, Zhu Y, Chan MHW. Direct imaging of electron transfer and its influence on superconducting pairing at FeSe/SrTiO 3 interface. SCIENCE ADVANCES 2018; 4:eaao2682. [PMID: 29556528 PMCID: PMC5856486 DOI: 10.1126/sciadv.aao2682] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Accepted: 02/07/2018] [Indexed: 05/31/2023]
Abstract
The exact mechanism responsible for the significant enhancement of the superconducting transition temperature (Tc) of monolayer iron selenide (FeSe) films on SrTiO3 (STO) over that of bulk FeSe is an open issue. We present the results of a coordinated study of electrical transport, low temperature electron energy-loss spectroscopy (EELS), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements on FeSe/STO films of different thicknesses. HAADF-STEM imaging together with EELS mapping across the FeSe/STO interface shows direct evidence of electrons transferred from STO to the FeSe layer. The transferred electrons were found to accumulate within the first two atomic layers of the FeSe films near the STO substrate. An additional Se layer is also resolved to reside between the FeSe film and the TiO x -terminated STO substrate. Our transport results found that a positive backgate applied from STO is particularly effective in enhancing Tc of the films while minimally changing the carrier density. This increase in Tc is due to the positive backgate that "pulls" the transferred electrons in FeSe films closer to the interface and thus enhances their coupling to interfacial phonons and also the electron-electron interaction within FeSe films.
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Affiliation(s)
- Weiwei Zhao
- Center for Nanoscale Science and Department of Physics, Pennsylvania State University, University Park, PA 16802–6300, USA
- State Key Laboratory of Advanced Welding and Joining and Research Center of Flexible Printed Electronic Technology, Harbin Institute of Technology, Shenzhen 518055, People’s Republic of China
| | - Mingda Li
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Francis Bitter Magnet Laboratory and Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Cui-Zu Chang
- Center for Nanoscale Science and Department of Physics, Pennsylvania State University, University Park, PA 16802–6300, USA
- Francis Bitter Magnet Laboratory and Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jue Jiang
- Center for Nanoscale Science and Department of Physics, Pennsylvania State University, University Park, PA 16802–6300, USA
| | - Lijun Wu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Chaoxing Liu
- Center for Nanoscale Science and Department of Physics, Pennsylvania State University, University Park, PA 16802–6300, USA
| | - Jagadeesh S. Moodera
- Francis Bitter Magnet Laboratory and Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Yimei Zhu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Moses H. W. Chan
- Center for Nanoscale Science and Department of Physics, Pennsylvania State University, University Park, PA 16802–6300, USA
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16
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Huang D, Webb TA, Song CL, Chang CZ, Moodera JS, Kaxiras E, Hoffman JE. Dumbbell Defects in FeSe Films: A Scanning Tunneling Microscopy and First-Principles Investigation. NANO LETTERS 2016; 16:4224-4229. [PMID: 27282020 DOI: 10.1021/acs.nanolett.6b01163] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The properties of iron-based superconductors (Fe-SCs) can be varied dramatically with the introduction of dopants and atomic defects. As a pressing example, FeSe, parent phase of the highest-Tc Fe-SC, exhibits prevalent defects with atomic-scale "dumbbell" signatures as imaged by scanning tunneling microscopy (STM). These defects spoil superconductivity when their concentration exceeds 2.5%. Resolving their chemical identity is a prerequisite to applications such as nanoscale patterning of superconducting/nonsuperconducting regions in FeSe as well as fundamental questions such as the mechanism of superconductivity and the path by which the defects destroy it. We use STM and density functional theory to characterize and identify the dumbbell defects. In contrast to previous speculations about Se adsorbates or substitutions, we find that an Fe-site vacancy is the most energetically favorable defect in Se-rich conditions and reproduces our observed STM signature. Our calculations shed light more generally on the nature of Se capping, the removal of Fe vacancies via annealing, and their ordering into a √5 × √5 superstructure in FeSe and related alkali-doped compounds.
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Affiliation(s)
| | - Tatiana A Webb
- Department of Physics & Astronomy, University of British Columbia , Vancouver, British Columbia V6T 1Z1, Canada
| | | | | | | | | | - Jennifer E Hoffman
- Department of Physics & Astronomy, University of British Columbia , Vancouver, British Columbia V6T 1Z1, Canada
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17
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Song CL, Zhang HM, Zhong Y, Hu XP, Ji SH, Wang L, He K, Ma XC, Xue QK. Observation of Double-Dome Superconductivity in Potassium-Doped FeSe Thin Films. PHYSICAL REVIEW LETTERS 2016; 116:157001. [PMID: 27127981 DOI: 10.1103/physrevlett.116.157001] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Indexed: 06/05/2023]
Abstract
We report on the emergence of two disconnected superconducting domes in alkali-metal potassium- (K-)doped FeSe ultrathin films grown on graphitized SiC(0001). The superconductivity exhibits hypersensitivity to K dosage in the lower-T_{c} dome, whereas in the heavily electron-doped higher-T_{c} dome it becomes spatially homogeneous and robust against disorder, supportive of a conventional Cooper-pairing mechanism. Furthermore, the heavily K-doped multilayer FeSe films all reveal a large superconducting gap of ∼14 meV, irrespective of film thickness, verifying the higher-T_{c} superconductivity only in the topmost FeSe layer. The unusual finding of a double-dome superconducting phase is a step towards the mechanistic understanding of superconductivity in FeSe-derived superconductors.
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Affiliation(s)
- Can-Li Song
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Hui-Min Zhang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Yong Zhong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xiao-Peng Hu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Shuai-Hua Ji
- 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
| | - Xu-Cun Ma
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
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