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Moore RG, Lu Q, Jeon H, Yao X, Smith T, Pai YY, Chilcote M, Miao H, Okamoto S, Li AP, Oh S, Brahlek M. Monolayer Superconductivity and Tunable Topological Electronic Structure at the Fe(Te,Se)/Bi 2 Te 3 Interface. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2210940. [PMID: 36921318 DOI: 10.1002/adma.202210940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 03/07/2023] [Indexed: 06/02/2023]
Abstract
The interface between 2D topological Dirac states and an s-wave superconductor is expected to support Majorana-bound states (MBS) that can be used for quantum computing applications. Realizing these novel states of matter and their applications requires control over superconductivity and spin-orbit coupling to achieve spin-momentum-locked topological interface states (TIS) which are simultaneously superconducting. While signatures of MBS have been observed in the magnetic vortex cores of bulk FeTe0.55 Se0.45 , inhomogeneity and disorder from doping make these signatures unclear and inconsistent between vortices. Here superconductivity is reported in monolayer (ML) FeTe1-y Sey (Fe(Te,Se)) grown on Bi2 Te3 by molecular beam epitaxy (MBE). Spin and angle-resolved photoemission spectroscopy (SARPES) directly resolve the interfacial spin and electronic structure of Fe(Te,Se)/Bi2 Te3 heterostructures. For y = 0.25, the Fe(Te,Se) electronic structure is found to overlap with the Bi2 Te3 TIS and the desired spin-momentum locking is not observed. In contrast, for y = 0.1, reduced inhomogeneity measured by scanning tunneling microscopy (STM) and a smaller Fe(Te,Se) Fermi surface with clear spin-momentum locking in the topological states are found. Hence, it is demonstrated that the Fe(Te,Se)/Bi2 Te3 system is a highly tunable platform for realizing MBS where reduced doping can improve characteristics important for Majorana interrogation and potential applications.
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Affiliation(s)
- Robert G Moore
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Qiangsheng Lu
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Hoyeon Jeon
- Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Xiong Yao
- Department of Physics and Astronomy, Rutgers the State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Tyler Smith
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Yun-Yi Pai
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Michael Chilcote
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Hu Miao
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Satoshi Okamoto
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - An-Ping Li
- Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Seongshik Oh
- Department of Physics and Astronomy, Rutgers the State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Matthew Brahlek
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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2
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Haastrup MJ, Bianchi M, Lammich L, Lauritsen JV. The interface of in-situgrown single-layer epitaxial MoS 2on SrTiO 3(001) and (111). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 35:194001. [PMID: 36827739 DOI: 10.1088/1361-648x/acbf19] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Accepted: 02/24/2023] [Indexed: 06/18/2023]
Abstract
SrTiO3(STO) is a versatile substrate with a high dielectric constant, which may be used in heterostructures with 2D materials, such as MoS2, to induce interesting changes to the electronic structure. STO single crystal substrates have previously been shown to support the growth of well-defined epitaxial single-layer (SL) MoS2crystals. The STO substrate is already known to renormalize the electronic bandgap of SL MoS2, but the electronic nature of the interface and its dependence on epitaxy are still unclear. Herein, we have investigated anin-situphysical vapor deposition (PVD) method, which could eliminate the need for ambient transfer between substrate preparation, subsequent MoS2growth and surface characterization. Based on this, we then investigate the structure and epitaxial alignment of pristine SL MoS2in various surface coverages grown on two STO substrates with a different initial surface lattice, the STO(001)(4 × 2) and STO(111)-(9/5 × 9/5) reconstructed surfaces, respectively. Scanning tunneling microscopy shows that epitaxial alignment of the SL MoS2is present for both systems, reflected by orientation of MoS2edges and a distinct moiré pattern visible on the MoS2(0001) basal place. Upon increasing the SL MoS2coverage, the presence of four distinct rotational domains on the STO(001) substrate, whilst only two on STO(111), is seen to control the possibilities for the formation of coherent MoS2domains with the same orientation. The presented methodology relies on standard PVD in ultra-high vacuum and it may be extended to other systems to help explore pristine two-dimensional transition metal dichalcogenide/STO systems in general.
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Affiliation(s)
- Mark J Haastrup
- Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
| | - Marco Bianchi
- Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
| | - Lutz Lammich
- Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
| | - Jeppe V Lauritsen
- Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
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3
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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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4
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Xu HS, Wu S, Zheng H, Yin R, Li Y, Wang X, Tang K. Research Progress of FeSe-based Superconductors Containing Ammonia/Organic Molecules Intercalation. Top Curr Chem (Cham) 2022; 380:11. [PMID: 35122164 DOI: 10.1007/s41061-022-00368-8] [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: 09/21/2021] [Accepted: 01/17/2022] [Indexed: 10/19/2022]
Abstract
As an important part of Fe-based superconductors, FeSe-based superconductors have become a hot field in condensed matter physics. The exploration and preparation of such superconducting materials form the basis of studying their physical properties. With the help of various alkali/alkaline-earth/rare-earth metals, different kinds of ammonia/organic molecules have been intercalated into the FeSe layer to form a large number of FeSe-based superconductors with diverse structures and different layer spacing. Metal cations can effectively provide carriers to the superconducting FeSe layer, thus significantly increasing the superconducting transition temperature. The orientation of organic molecules often plays an important role in structural modification and can be used to fine-tune superconductivity. This review introduces the crystal structures and superconducting properties of several typical FeSe-based superconductors containing ammonia/organic molecules intercalation discovered in recent years, and the effects of FeSe layer spacing and superconducting transition temperature are briefly summarized.
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Affiliation(s)
- Han-Shu Xu
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, 230026, People's Republic of China.
| | - Shusheng Wu
- Department of Chemistry, University of Science and Technology of China, Hefei, 230026, People's Republic of China
| | - Hui Zheng
- Department of Chemistry, University of Science and Technology of China, Hefei, 230026, People's Republic of China
| | - Ruotong Yin
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, 230026, People's Republic of China
| | - Yuanji Li
- Department of Physics, University of Science and Technology of China, Hefei, 230026, People's Republic of China
| | - Xiaoxiong Wang
- College of Physics Science, Qingdao University, Qingdao, 266071, People's Republic of China.
| | - Kaibin Tang
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, 230026, People's Republic of China. .,Department of Chemistry, University of Science and Technology of China, Hefei, 230026, People's Republic of China.
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5
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Xing Y, Yang P, Ge J, Yan J, Luo J, Ji H, Yang Z, Li Y, Wang Z, Liu Y, Yang F, Qiu P, Xi C, Tian M, Liu Y, Lin X, Wang J. Extrinsic and Intrinsic Anomalous Metallic States in Transition Metal Dichalcogenide Ising Superconductors. NANO LETTERS 2021; 21:7486-7494. [PMID: 34460267 DOI: 10.1021/acs.nanolett.1c01426] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The metallic ground state in two-dimensional (2D) superconductors has attracted much attention but is still under intense scrutiny. Especially, the measurements in the ultralow temperature region are challenging for 2D superconductors due to the sensitivity to external perturbations. In this work, the resistance saturation induced by external noise, named as the "extrinsic anomalous metallic state", is observed in 2D transition metal dichalcogenide (TMD) superconductor 4Ha-TaSe2 nanodevices. However, with further decreasing temperature, credible evidence of the intrinsic anomalous metallic state is obtained by adequately filtering external radiation. Our work indicates that, at ultralow temperatures, the anomalous metallic state can be experimentally revealed as the quantum ground state in 2D crystalline TMD superconductors. Besides, Ising superconductivity revealed by ultrahigh in-plane critical field (Bc2∥) going beyond the Pauli paramagnetic limit (Bp) is detected in 4Ha-TaSe2, from the one-unit-cell device to the bulk situation, which might be due to the weak coupling between the TaSe2 submonolayers.
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Affiliation(s)
- Ying Xing
- State Key Laboratory of Heavy Oil Processing, College of New Energy and Materials, China University of Petroleum, Beijing 102249, China
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Pu Yang
- State Key Laboratory of Heavy Oil Processing, College of New Energy and Materials, China University of Petroleum, Beijing 102249, China
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Jun Ge
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Jiaojie Yan
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Jiawei Luo
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Haoran Ji
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Zeyan Yang
- State Key Laboratory of Heavy Oil Processing, College of New Energy and Materials, China University of Petroleum, Beijing 102249, China
| | - Yongjie Li
- State Key Laboratory of Heavy Oil Processing, College of New Energy and Materials, China University of Petroleum, Beijing 102249, China
| | - Zijia Wang
- State Key Laboratory of Heavy Oil Processing, College of New Energy and Materials, China University of Petroleum, Beijing 102249, China
| | - Yanzhao Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Feng Yang
- State Key Laboratory of Heavy Oil Processing, College of New Energy and Materials, China University of Petroleum, Beijing 102249, China
| | - Ping Qiu
- State Key Laboratory of Heavy Oil Processing, College of New Energy and Materials, China University of Petroleum, Beijing 102249, China
| | - Chuanying Xi
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, China
| | - Mingliang Tian
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, China
| | - Yi Liu
- Department of Physics, Renmin University of China, Beijing 100872, China
| | - Xi Lin
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
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6
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Krzton-Maziopa A. Intercalated Iron Chalcogenides: Phase Separation Phenomena and Superconducting Properties. Front Chem 2021; 9:640361. [PMID: 34239856 PMCID: PMC8259132 DOI: 10.3389/fchem.2021.640361] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 04/07/2021] [Indexed: 11/15/2022] Open
Abstract
Organic molecule-intercalated layered iron-based monochalcogenides are presently the subject of intense research studies due to the linkage of their fascinating magnetic and superconducting properties to the chemical nature of guests present in the structure. Iron chalcogenides have the ability to host various organic species (i.e., solvates of alkali metals and the selected Lewis bases or long-chain alkylammonium cations) between the weakly bound inorganic layers, which opens up the possibility for fine tuning the magnetic and electrical properties of the intercalated phases by controlling both the doping level and the type/shape and orientation of the organic molecules. In recent years, significant progress has been made in the field of intercalation chemistry, expanding the gallery of intercalated superconductors with new hybrid inorganic–organic phases characterized by transition temperatures to a superconducting state as high as 46 K. A typical synthetic approach involves the low-temperature intercalation of layered precursors in the presence of liquid amines, and other methods, such as electrochemical intercalation, intercalant or ion exchange, and direct solvothermal growths from anhydrous amine-based media, are also being developed. Large organic guests, while entering a layered structure on intercalation, push off the inorganic slabs and modify the geometry of their internal building blocks (edge-sharing iron chalcogenide tetrahedrons) through chemical pressure. The chemical nature and orientation of organic molecules between the inorganic layers play an important role in structural modification and may serve as a tool for the alteration of the superconducting properties. A variety of donor species well-matched with the selected alkali metals enables the adjustment of electron doping in a host structure offering a broad range of new materials with tunable electric and magnetic properties. In this review, the main aspects of intercalation chemistry are discussed, involving the influence of the chemical and electrochemical nature of intercalating species on the crystal structure and critical issues related to the superconducting properties of the hybrid inorganic–organic phases. Mutual relations between the host and organic guests lead to a specific ordering of molecular species between the host layers, and their effect on the electronic structure of the host will be also argued. A brief description of a critical assessment of the association of the most effective chemical and electrochemical methods, which lead to the preparation of nanosized/microsized powders and single crystals of molecularly intercalated phases, with the ease of preparation of phase pure materials, crystal sizes, and the morphology of final products is given together with a discussion of the stability of the intercalated materials connected with the volatility of organic solvents and a possible degradation of host materials.
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7
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Xu Y, Rong H, Wang Q, Wu D, Hu Y, Cai Y, Gao Q, Yan H, Li C, Yin C, Chen H, Huang J, Zhu Z, Huang Y, Liu G, Xu Z, Zhao L, Zhou XJ. Spectroscopic evidence of superconductivity pairing at 83 K in single-layer FeSe/SrTiO 3 films. Nat Commun 2021; 12:2840. [PMID: 33990574 PMCID: PMC8121788 DOI: 10.1038/s41467-021-23106-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 04/13/2021] [Indexed: 12/02/2022] Open
Abstract
Single-layer FeSe films grown on the SrTiO3 substrate (FeSe/STO) have attracted much attention because of their possible record-high superconducting critical temperature (Tc) and distinct electronic structures. However, it has been under debate on how high its Tc can really reach due to the inconsistency of the results from different measurements. Here we report spectroscopic evidence of superconductivity pairing at 83 K in single-layer FeSe/STO films. By preparing high-quality single-layer FeSe/STO films, we observe strong superconductivity-induced Bogoliubov back-bending bands that extend to rather high binding energy ~ 100 meV by high-resolution angle-resolved photoemission measurements. They provide a new definitive benchmark of superconductivity pairing that is directly observed up to 83 K. Moreover, we find that the pairing state can be further divided into two temperature regions. These results indicate that either Tc as high as 83 K is achievable, or there is a pseudogap formation from superconductivity fluctuation in single-layer FeSe/STO films. How high the superconducting transition temperature can reach in single layer FeSe/SrTiO3 films has been under debate. Here, the authors use Bogoliubov back-bending bands as a benchmark and demonstrate that superconductivity pairing can be realized up to 83 K in this system.
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Affiliation(s)
- Yu Xu
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Hongtao Rong
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Qingyan Wang
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China. .,University of Chinese Academy of Sciences, Beijing, China.
| | - Dingsong Wu
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yong Hu
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yongqing Cai
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Qiang Gao
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Hongtao Yan
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Cong Li
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Chaohui Yin
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Hao Chen
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Jianwei Huang
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Zhihai Zhu
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yuan Huang
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Guodong Liu
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China.,Songshan Lake Materials Laboratory, Dongguan, China
| | - Zuyan Xu
- Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Lin Zhao
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China. .,University of Chinese Academy of Sciences, Beijing, China. .,Songshan Lake Materials Laboratory, Dongguan, China.
| | - X J Zhou
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China. .,University of Chinese Academy of Sciences, Beijing, China. .,Songshan Lake Materials Laboratory, Dongguan, China. .,Beijing Academy of Quantum Information Sciences, Beijing, China.
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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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Unusual Temperature Evolution of Quasiparticle Band Dispersion in Electron-Doped FeSe Films. Symmetry (Basel) 2021. [DOI: 10.3390/sym13020155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The discovery of high-temperature (high-Tc) superconductivity in one-monolayer FeSe on SrTiO3 has attracted tremendous attention. Subsequent studies suggested the importance of cooperation between intra-FeSe-layer and interfacial interactions to enhance Tc. However, the nature of intra-FeSe-layer interactions, which would play a primary role in determining the pairing symmetry, remains unclear. Here we have performed high-resolution angle-resolved photoemission spectroscopy of one-monolayer and alkaline-metal-deposited multilayer FeSe films on SrTiO3, and determined the evolution of quasiparticle band dispersion across Tc. We found that the band dispersion in the superconducting state deviates from the Bogoliubov-quasiparticle dispersion expected from the normal-state band dispersion with a constant gap size. This suggests highly anisotropic pairing originating from small momentum transfer and/or mass renormalization due to electron–boson coupling. This band anomaly is interpreted in terms of the electronic interactions within the FeSe layers that may be related to the high-Tc superconductivity in electron-doped FeSe.
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10
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Han X, Wu Y, Xiao H, Zhang M, Gao M, Liu Y, Wang J, Hu T, Xie X, Di Z. Disorder-Induced Quantum Griffiths Singularity Revealed in an Artificial 2D Superconducting System. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:1902849. [PMID: 33101841 PMCID: PMC7578859 DOI: 10.1002/advs.201902849] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Revised: 07/26/2020] [Indexed: 06/02/2023]
Abstract
Disorder-induced Griffiths singularity of quantum phase transition (QPT) is a crucial issue in 2D superconductors (2DSC). In a superconducting system, the strength of disorder is found to be associated with the vortex pinning energy, which is closely related to the quantum Griffiths singularity; however, a direct study to elucidate the role of vortex pinning energy on the quantum Griffiths singularity in 2DSC remains to be undertaken. Here, an artificial 2DSC system is designed by randomly depositing superconducting nanoislands on 2Delectron gas (2DEG). Quantum Griffiths singularity is present in a graphene/Pb-islands-array hybrid, where the superconducting behavior transits to weakly localized metallic behavior induced by the vertical magnetic field and exhibits critical behavior with a diverging dynamical critical exponent approaching zero temperature. Compared to the study of graphene/Sn-islands-array hybrid where the sharp QPT is observed, the vortex pinning energy acquired from the Arrhenius plot analysis is greater in graphene/Pb-islands-array hybrid, which may contribute to the presence of the quantum Griffiths singularity. This work may provide a comprehensive interpretation of the QPT in 2DSC.
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Affiliation(s)
- Xiaowen Han
- State Key Laboratory of Functional Materials for InformaticsShanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences865 Changning RoadShanghai200050China
- Center of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of SciencesBeijing100049China
| | - Yufeng Wu
- State Key Laboratory of Functional Materials for InformaticsShanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences865 Changning RoadShanghai200050China
- Center of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of SciencesBeijing100049China
- CAS Center for Excellence in Superconducting Electronics (CENSE)Shanghai200050China
| | - Hong Xiao
- Center for High Pressure Science and Technology Advanced ResearchBeijing100094China
| | - Miao Zhang
- State Key Laboratory of Functional Materials for InformaticsShanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences865 Changning RoadShanghai200050China
| | - Min Gao
- State Key Laboratory of Functional Materials for InformaticsShanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences865 Changning RoadShanghai200050China
- Center of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of SciencesBeijing100049China
| | - Yi Liu
- International Center for Quantum MaterialsSchool of PhysicsPeking UniversityBeijing100871China
- Collaborative Innovation Center of Quantum MatterBeijing100871China
| | - Jian Wang
- International Center for Quantum MaterialsSchool of PhysicsPeking UniversityBeijing100871China
- Collaborative Innovation Center of Quantum MatterBeijing100871China
- CAS Center for Excellence in Topological Quantum ComputationUniversity of Chinese Academy of SciencesBeijing100190China
- Beijing Academy of Quantum Information SciencesWest Bld. #3, No. 10 Xibeiwang East Rd., Haidian DistrictBeijing100193China
| | - Tao Hu
- State Key Laboratory of Functional Materials for InformaticsShanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences865 Changning RoadShanghai200050China
- CAS Center for Excellence in Superconducting Electronics (CENSE)Shanghai200050China
- Beijing Academy of Quantum Information SciencesWest Bld. #3, No. 10 Xibeiwang East Rd., Haidian DistrictBeijing100193China
| | - Xiaoming Xie
- State Key Laboratory of Functional Materials for InformaticsShanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences865 Changning RoadShanghai200050China
- CAS Center for Excellence in Superconducting Electronics (CENSE)Shanghai200050China
| | - Zengfeng Di
- State Key Laboratory of Functional Materials for InformaticsShanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences865 Changning RoadShanghai200050China
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11
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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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12
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Abstract
Emergent electronic phenomena in iron-based superconductors have been at the forefront of condensed matter physics for more than a decade. Much has been learned about the origins and intertwined roles of ordered phases, including nematicity, magnetism, and superconductivity, in this fascinating class of materials. In recent years, focus has been centered on the peculiar and highly unusual properties of FeSe and its close cousins. This family of materials has attracted considerable attention due to the discovery of unexpected superconducting gap structures, a wide range of superconducting critical temperatures, and evidence for nontrivial band topology, including associated spin-helical surface states and vortex-induced Majorana bound states. Here, we review superconductivity in iron chalcogenide superconductors, including bulk FeSe, doped bulk FeSe, FeTe1−xSex, intercalated FeSe materials, and monolayer FeSe and FeTe1−xSex on SrTiO3. We focus on the superconducting properties, including a survey of the relevant experimental studies, and a discussion of the different proposed theoretical pairing scenarios. In the last part of the paper, we review the growing recent evidence for nontrivial topological effects in FeSe-related materials, focusing again on interesting implications for superconductivity.
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13
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Pedersen AK, Ichinokura S, Tanaka T, Shimizu R, Hitosugi T, Hirahara T. Interfacial Superconductivity in FeSe Ultrathin Films on SrTiO_{3} Probed by In Situ Independently Driven Four-Point-Probe Measurements. PHYSICAL REVIEW LETTERS 2020; 124:227002. [PMID: 32567930 DOI: 10.1103/physrevlett.124.227002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 05/18/2020] [Indexed: 06/11/2023]
Abstract
We investigated the superconducting transport properties of the one-unit-cell FeSe ultrathin films epitaxially grown on undoped SrTiO_{3}(001) (STO) with a well-defined surface structure by in situ independently-driven four-point-probe measurements. Our results unambiguously revealed the detection of the two-dimensional electrical conduction of the films without parallel conduction through the underlying substrate, both in the normal and superconducting states. The monolayer film exhibited a superconducting transition at an onset temperature of 40 K. Surprisingly, the onset of superconductivity was constantly observed at 40 K even for three- and five-unit-cell-thick FeSe films, even though the normal resistivity decreased with increasing thickness. These results agree with the picture of the interfacial superconductivity, where only the FeSe/STO interface and/or the adjacent first layer of FeSe becomes superconducting while the upper layers stay in the normal metallic state. The observed T_{c} is much lower than that reported by a previous in situ transport measurement for FeSe/Nb:STO but consistent with the results obtained by ex situ measurements for FeSe-undoped STO with a capping layer. This suggests that the capping layer is not an essential factor to limit T_{c}. We rather propose that the charge transfer from the doped substrate has a key role to achieve the higher temperature superconductivity in the one-unit-cell FeSe.
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Affiliation(s)
- Asger K Pedersen
- Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan
| | - Satoru Ichinokura
- Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan
| | - Tomoaki Tanaka
- Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan
| | - Ryota Shimizu
- Department of Applied Chemistry, Tokyo Institute of Technology, Tokyo 152-8550, Japan
| | - Taro Hitosugi
- Department of Applied Chemistry, Tokyo Institute of Technology, Tokyo 152-8550, Japan
| | - Toru Hirahara
- Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan
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14
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Cui W, Zheng C, Zhang L, Kang Z, Li L, Cai X, Zhao D, Hu X, Chen X, Wang Y, Wang L, Wang Y, Ma X, Xue QK. An in situ electrical transport measurement system under ultra-high vacuum. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:063902. [PMID: 32611039 DOI: 10.1063/5.0004304] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 05/29/2020] [Indexed: 06/11/2023]
Abstract
Low-dimensional materials exhibit exotic properties and have attracted widespread attention. However, many low-dimensional materials are highly sensitive to air, making it challenging to investigate their intrinsic properties with ex situ measurements. To overcome such challenges, here, we developed a system combined with sample growth, electrode deposition, and in situ electrical transport measurement under ultra-high vacuum condition. The in situ deposition of electrodes enables desired ohmic electrical contacts between the probes and samples, which allows continuous temperature dependent resistance (R-T) measurements. Combined with a scanning tunneling microscope, surface morphology, electronic structure, and electrical transport properties of the same sample can be systematically investigated. We demonstrate the performance of this in situ electrical transport measurement system with three-unit-cell thick FeSe films grown on Nb-doped SrTiO3(001) substrates, where a low-noise R-T curve with a zero-resistance superconducting transition temperature of ∼30 K is observed.
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Affiliation(s)
- Wenqiang Cui
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Cheng Zheng
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Liguo Zhang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Zhixin Kang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Luxin Li
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xinqiang Cai
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Dapeng Zhao
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xiaopeng Hu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xi Chen
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Yilin Wang
- Center of Nanoelectronics, School of Microelectronics, Shandong University, Jinan 250100, China
| | - Lili Wang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Yayu Wang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xucun Ma
- 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
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15
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Xu X, Zhang S, Zhu X, Guo J. Superconductivity enhancement in FeSe/SrTiO 3: a review from the perspective of electron-phonon coupling. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:343003. [PMID: 32241002 DOI: 10.1088/1361-648x/ab85f0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 04/02/2020] [Indexed: 06/11/2023]
Abstract
Single-layer FeSe films grown on SrTiO3, with the highest superconducting transition temperature (TC) among all the iron-based superconductors, serves as an ideal platform for studying the microscopic mechanisms of high-TCsuperconductivity. The significant role of interfacial coupling has been widely recognized, while the precise nature of theTCenhancement remains open. In this review, we focus on the investigations of the interfacial coupling in FeSe/SrTiO3from the perspective of electron-phonon coupling (EPC). The main content will include an overview of the experimental measurements associated with different theoretical models and arguments about the EPC. Especially, besides the discussions of EPC based on the measurements of electronic states, we will emphasize the analyses based on phonon measurements. A uniform picture about the nature of the EPC and its relation to theTCenhancement in FeSe/SrTiO3has still not achieved, which should be the key for further studies aiming to the in-depth understanding of high-TCsuperconductivity and the discovery of new superconductors with even enhancedTC.
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Affiliation(s)
- Xiaofeng Xu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Shuyuan Zhang
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, United States of America
| | - Xuetao Zhu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Jiandong Guo
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, People's Republic of China
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16
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Seifert P, Lu X, Stepanov P, Durán Retamal JR, Moore JN, Fong KC, Principi A, Efetov DK. Magic-Angle Bilayer Graphene Nanocalorimeters: Toward Broadband, Energy-Resolving Single Photon Detection. NANO LETTERS 2020; 20:3459-3464. [PMID: 32315186 DOI: 10.1021/acs.nanolett.0c00373] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Because of the ultralow photon energies at mid-infrared and terahertz frequencies, in these bands photodetectors are notoriously underdeveloped, and broadband single photon detectors (SPDs) are nonexistent. Advanced SPDs exploit thermal effects in nanostructured superconductors, and their performance is currently limited to the more energetic near-infrared photons due to their high electronic heat capacity. Here, we demonstrate a superconducting magic-angle bilayer graphene (MAG) device that is theoretically capable of detecting single photons of ultralow energies by utilizing its record-low heat capacity and sharp superconducting transition. We theoretically quantify its calorimetric photoresponse and estimate its detection limits. This device allows the detection of ultrabroad range single photons from the visible to sub-terahertz with a response time around 4 ns and energy resolution better than 1 THz. These attributes position MAG as an exceptional material for long-wavelength single photon sensing, which could revolutionize such disparate fields as quantum information processing and radio astronomy.
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Affiliation(s)
- Paul Seifert
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain
| | - Xiaobo Lu
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain
| | - Petr Stepanov
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain
| | - José Ramón Durán Retamal
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain
| | - John N Moore
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain
| | - Kin-Chung Fong
- Quantum Information Processing Group, Raytheon BBN Technologies, Cambridge, Massachusetts 02138, United States
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Alessandro Principi
- Department of Physics and Astronomy, The University of Manchester, Oxford Road, M13 9PL, Manchester, United Kingdom
| | - Dmitri K Efetov
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain
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17
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Zhang RX, Cole WS, Wu X, Das Sarma S. Higher-Order Topology and Nodal Topological Superconductivity in Fe(Se,Te) Heterostructures. PHYSICAL REVIEW LETTERS 2019; 123:167001. [PMID: 31702343 DOI: 10.1103/physrevlett.123.167001] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 08/28/2019] [Indexed: 06/10/2023]
Abstract
We show, theoretically, that a heterostructure of monolayer FeTe_{1-x}Se_{x}-a superconducting quantum spin Hall material-with a monolayer of FeTe-a bicollinear antiferromagnet-realizes a higher order topological superconductor phase characterized by emergent Majorana zero modes pinned to the sample corners. We provide a minimal effective model for this system, analyze the origin of higher order topology, and fully characterize the topological phase diagram. Despite the conventional s-wave pairing, we find a rather surprising emergence of a novel topological nodal superconductor in the phase diagram. Featured by edge-dependent Majorana flat bands, the topological nodal phase is protected by an antiferromagnetic chiral symmetry. We also discuss the experimental feasibility, the estimation of realistic model parameters, and the robustness of the Majorana corner modes against magnetic and potential disorder. Our work provides a new experimentally feasible high-temperature platform for both higher order topology and non-Abelian Majorana physics.
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Affiliation(s)
- Rui-Xing Zhang
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
| | - William S Cole
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
| | - Xianxin Wu
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland Campus Süd, Würzburg 97074, Germany
| | - S Das Sarma
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
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18
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Ding C, Gong G, Liu Y, Zheng F, Zhang Z, Yang H, Li Z, Xing Y, Ge J, He K, Li W, Zhang P, Wang J, Wang L, Xue QK. Signature of Superconductivity in Orthorhombic CoSb Monolayer Films on SrTiO 3(001). ACS NANO 2019; 13:10434-10439. [PMID: 31460747 DOI: 10.1021/acsnano.9b04223] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We prepare orthorhombic CoSb monolayer films on SrTiO3(001) substrate by molecular beam epitaxy and observe symmetric gap around the Fermi level with coherence peaks at ± (6-7) meV by in situ scanning tunneling spectroscopy. Ex situ magnetization measurements of the films protected by Te and Si films consistently reveal a diamagnetic transition at 14 K. These results suggest the occurrence of superconductivity in orthorhombic CoSb monolayers on SrTiO3(001).
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Affiliation(s)
- Cui Ding
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
| | - Guanming Gong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
| | - Yanzhao Liu
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Fawei Zheng
- Institute of Applied Physics and Computational Mathematics , Beijing 100088 , China
| | - Zhiyu Zhang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
| | - Haohao Yang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
| | - Zhe Li
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
| | - Ying Xing
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
- Department of Materials Science and Engineering, School of New Energy and Materials , China University of Petroleum , Beijing 102249 , China
| | - Jun Ge
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Ke He
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
- Collaborative Innovation Center of Quantum Matter , Beijing 100084 , China
- Beijing Academy of Quantum Information Sciences , Beijing 100193 , China
| | - Wei Li
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
- Collaborative Innovation Center of Quantum Matter , Beijing 100084 , China
| | - Ping Zhang
- Institute of Applied Physics and Computational Mathematics , Beijing 100088 , China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
- Collaborative Innovation Center of Quantum Matter , Beijing 100084 , China
- CAS Center for Excellence in Topological Quantum Computation , University of Chinese Academy of Sciences , Beijing 100190 , China
- Beijing Academy of Quantum Information Sciences , Beijing 100193 , China
| | - Lili Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
- Collaborative Innovation Center of Quantum Matter , Beijing 100084 , China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , China
- Collaborative Innovation Center of Quantum Matter , Beijing 100084 , China
- Beijing Academy of Quantum Information Sciences , Beijing 100193 , China
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19
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Kang KT, Park J, Suh D, Choi WS. Synergetic Behavior in 2D Layered Material/Complex Oxide Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1803732. [PMID: 30589101 DOI: 10.1002/adma.201803732] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 09/18/2018] [Indexed: 05/28/2023]
Abstract
The marriage between a 2D layered material (2DLM) and a complex transition metal oxide (TMO) results in a variety of physical and chemical phenomena that cannot be achieved in either material alone. Interesting recent discoveries in systems such as graphene/SrTiO3 , graphene/LaAlO3 /SrTiO3 , graphene/ferroelectric oxide, MoS2 /SrTiO3 , and FeSe/SrTiO3 heterostructures include voltage scaling in field-effect transistors, charge state coupling across an interface, quantum conductance probing of the electrochemical activity, novel memory functions based on charge traps, and greatly enhanced superconductivity. In this context, various properties and functionalities appearing in numerous different 2DLM/TMO heterostructure systems are reviewed. The results imply that the multidimensional heterostructure approach based on the disparate material systems leads to an entirely new platform for the study of condensed matter physics and materials science. The heterostructures are also highly relevant technologically as each constituent material is a promising candidate for next-generation optoelectronic devices.
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Affiliation(s)
- Kyeong Tae Kang
- Department of Physics, Sungkyunkwan University, Suwon, 16419, Korea
| | - Jeongmin Park
- Department of Energy Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Dongseok Suh
- Department of Energy Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Woo Seok Choi
- Department of Physics, Sungkyunkwan University, Suwon, 16419, Korea
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20
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Liu C, Wang G, Wang J. Manipulating the particle-hole symmetry of quasiparticle bound states in geometric-size-varying Fe clusters on one-unit-cell FeSe/SrTiO 3(0 0 1). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:285002. [PMID: 30947147 DOI: 10.1088/1361-648x/ab1630] [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
The particle-hole symmetry (PHS) of quasiparticle bound states, which is generally expected in theory, is present or absent experimentally in a seemingly irregular manner, with the physical origin little understood yet. Here, we report a study on the bound states induced by Fe clusters with different sizes on one-unit-cell (1-UC) FeSe/SrTiO3(0 0 1) by in situ scanning tunneling spectroscopy. Statistically, on the larger-scale cluster, a pair of bias-symmetric minipeaks are detected within the superconducting-gap energies. As increasing temperature, the minipeak states show negligible energy dispersion. The temperature-independent bias-symmetric minipeaks are identified as the quasiparticle bound states that preserve the PHS. However, on the smaller-scale cluster, the bound state appears as a single resonance instead. These results reveal a geometric-size-tuning effect of the PHS, which may help reconcile the contradiction between the superconductivity theory and the PHS-breaking experiments.
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Affiliation(s)
- Chaofei Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
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21
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Tang F, Wang P, Wang P, Gan Y, Gu GD, Zhang W, He M, Zhang L. Quasi-2D superconductivity in FeTe 0.55Se 0.45 ultrathin film. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:265702. [PMID: 30925488 DOI: 10.1088/1361-648x/ab14c3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Iron-chalcogenide FeTe0.55Se0.45 was found to be a promising topological superconducting candidate recently, which may host Majorana bound state in the vortex core and thus attracts intensive research interests in this material. In this report, mechanically exfoliated FeTe0.55Se0.45 superconducting thin films close to the two-dimensional (2D) limit, i.e. sample thickness is on the order of coherence length, were studied systematically by means of electrical transport and point-contact Andreev-reflection spectroscopy (PCARS) measurements. The quasi-2D nature of FeTe0.55Se0.45 thin films is evidenced by the observation of Berezinskii-Kosterlitz-Thouless (BKT) transition and anisotropic upper critical fields in the vicinity of superconducting transition. Compared to bulk samples, we found that the superconducting transition temperature is only slightly suppressed even for films down to 5 nm. The superconducting gap symmetry remains unchanged and the gap size is weakly affected by tailoring thickness. Our findings suggest that the superconductivity of FeTe0.55Se0.45 thin films is rather robust against reduced dimensions. It provides a novel platform for device applications for quantum computations in combination with possible realization of Majorana modes in this material.
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Affiliation(s)
- Fangdong Tang
- Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, People's Republic of China. Department of Physics, Southern University of Science and Technology, Shenzhen Institute for Quantum Science and Engineering, Shenzhen, 518055, People's Republic of China
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22
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Liu C, Wang Z, Ye S, Chen C, Liu Y, Wang Q, Wang QH, Wang J. Detection of Bosonic Mode as a Signature of Magnetic Excitation in One-Unit-Cell FeSe on SrTiO 3. NANO LETTERS 2019; 19:3464-3472. [PMID: 31117746 DOI: 10.1021/acs.nanolett.9b00144] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A "fingerprint" of Cooper pairing mediated by collective bosonic excitation mode is the reconstruction of the quasiparticle-density-of-states (DOS) spectrum with an additional "dip-hump" structure located outside the superconducting coherence peak. Here, we report an in situ scanning tunneling spectroscopy study of one-unit-cell (1-UC) FeSe film on a SrTiO3(001) substrate. In the quasiparticle-DOS spectrum, the bosonic excitation mode characterized by the dip-hump structure is detected outside the larger superconducting gap. Statistically, the excitation mode shows an anticorrelation with pairing strength in magnitude and yields an energy scale upper-bounded by twice the superconducting gap. The observation coincides with the characteristics of magnetic resonance in cuprates and iron-based superconductors. Furthermore, the local response of superconducting spectra to magnetically distinct Se defects all exhibits the induced in-gap quasiparticle bound states, indicating an unconventional sign-reversing pairing over the Fermi surface in 1-UC FeSe. These results clarify the magnetic nature of the bosonic excitation mode and reveal a signature of electron-magnetic-excitation coupling in 1-UC FeSe/SrTiO3(001) besides the previously established pairing channel of electron-phonon interaction.
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Affiliation(s)
- Chaofei Liu
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Ziqiao Wang
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Shusen Ye
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Cheng Chen
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Yi Liu
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Qingyan Wang
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | | | - Jian Wang
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871 , China
- CAS Center for Excellence in Topological Quantum Computation , University of Chinese Academy of Sciences , Beijing 100190 , China
- Beijing Academy of Quantum Information Sciences , Beijing 100193 , China
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23
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Giant thermoelectric power factor in ultrathin FeSe superconductor. Nat Commun 2019; 10:825. [PMID: 30778077 PMCID: PMC6379375 DOI: 10.1038/s41467-019-08784-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Accepted: 01/25/2019] [Indexed: 11/17/2022] Open
Abstract
The thermoelectric effect is attracting a renewed interest as a concept for energy harvesting technologies. Nanomaterials have been considered a key to realize efficient thermoelectric conversions owing to the low dimensional charge and phonon transports. In this regard, recently emerging two-dimensional materials could be promising candidates with novel thermoelectric functionalities. Here we report that FeSe ultrathin films, a high-Tc superconductor (Tc; superconducting transition temperature), exhibit superior thermoelectric responses. With decreasing thickness d, the electrical conductivity increases accompanying the emergence of high-Tc superconductivity; unexpectedly, the Seebeck coefficient α shows a concomitant increase as a result of the appearance of two-dimensional natures. When d is reduced down to ~1 nm, the thermoelectric power factor at 50 K and room temperature reach unprecedented values as high as 13,000 and 260 μW cm−1 K−2, respectively. The large thermoelectric effect in high Tc superconductors indicates the high potential of two-dimensional layered materials towards multi-functionalization. In an effort to optimize the performance of two-dimensional materials for thermoelectric generation, compounds with advantageous intrinsic properties must be identified. Here, the authors report large thermoelectric effect in ultrathin FeSe thin films with high Tc superconductivity.
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24
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Yang M, Yan C, Ma Y, Li L, Cen C. Light induced non-volatile switching of superconductivity in single layer FeSe on SrTiO 3 substrate. Nat Commun 2019; 10:85. [PMID: 30622274 PMCID: PMC6325130 DOI: 10.1038/s41467-018-08024-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 12/10/2018] [Indexed: 11/09/2022] Open
Abstract
The capability of controlling superconductivity by light is highly desirable for active quantum device applications. Since superconductors rarely exhibit strong photoresponses, and optically sensitive materials are often not superconducting, efficient coupling between these two characters can be very challenging in a single material. Here we show that, in FeSe/SrTiO3 heterostructures, the superconducting transition temperature in FeSe monolayer can be effectively raised by the interband photoexcitations in the SrTiO3 substrate. Attributed to a light induced metastable polar distortion uniquely enabled by the FeSe/SrTiO3 interface, this effect only requires a less than 50 µW cm-2 continuous-wave light field. The fast optical generation of superconducting zero resistance state is non-volatile but can be rapidly reversed by applying voltage pulses to the back of SrTiO3 substrate. The capability of switching FeSe repeatedly and reliably between normal and superconducting states demonstrate the great potential of making energy-efficient quantum optoelectronics at designed correlated interfaces.
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Affiliation(s)
- Ming Yang
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia, 26506, USA.,National Key Laboratory of Science and Technology on Power Sources, Tianjin Institute of Power Sources, Tianjin, 300384, P. R. China
| | - Chenhui Yan
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia, 26506, USA
| | - Yanjun Ma
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia, 26506, USA
| | - Lian Li
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia, 26506, USA.
| | - Cheng Cen
- Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia, 26506, USA.
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25
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Kouno S, Sato Y, Katayama Y, Ichinose A, Asami D, Nabeshima F, Imai Y, Maeda A, Ueno K. Superconductivity at 38 K at an electrochemical interface between an ionic liquid and FeSe 0.8Te 0.2 on various substrates. Sci Rep 2018; 8:14731. [PMID: 30283006 PMCID: PMC6170459 DOI: 10.1038/s41598-018-33121-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 09/13/2018] [Indexed: 11/30/2022] Open
Abstract
Superconducting FeSe0.8Te0.2 thin films on SrTiO3, LaAlO3 and CaF2 substrates were electrochemically etched in an ionic liquid, DEME-TFSI, electrolyte with a gate bias of 5 V. Superconductivity at 38 K was observed on all substrates after the etching of films with a thickness greater than 30 nm, despite the different Tc values of 8 K, 12 K and 19 K observed before etching on SrTiO3, LaAlO3 and CaF2 substrates, respectively. Tc returned to its original value with the removal of the gate bias. The observation of Tc enhancement for these thick films indicates that the Tc enhancement is unrelated to any interfacial effects between the film and the substrate. The sheet resistance and Hall coefficient of the surface conducting layer were estimated from the gate bias dependence of the transport properties. The sheet resistances of the surface conducting layers of the films on LaAlO3 and CaF2 showed identical temperature dependence, and the Hall coefficient was found to be almost independent of temperature and to take values of −0.05 to −0.2 m2/C, corresponding to 4–17 electrons per FeSe0.8Te0.2 unit cell area in two dimensions. These common transport properties on various substrates suggest that the superconductivity at 38 K appears in the surface conducting layer as a result of an electrochemical reaction between the surface of the FeSe0.8Te0.2 thin film and the ionic liquid electrolyte.
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Affiliation(s)
- Shunsuke Kouno
- Department of Basic Science, University of Tokyo, Meguro, Tokyo, 153-8902, Japan
| | - Yohei Sato
- Department of Basic Science, University of Tokyo, Meguro, Tokyo, 153-8902, Japan
| | - Yumiko Katayama
- Department of Basic Science, University of Tokyo, Meguro, Tokyo, 153-8902, Japan
| | - Ataru Ichinose
- Central Research Institute of Electric Power Industry, Yokosuka, Kanagawa, 240-0196, Japan
| | - Daisuke Asami
- Department of Basic Science, University of Tokyo, Meguro, Tokyo, 153-8902, Japan
| | - Fuyuki Nabeshima
- Department of Basic Science, University of Tokyo, Meguro, Tokyo, 153-8902, Japan
| | - Yoshinori Imai
- Department of Physics, Tohoku University, Sendai, 980-8578, Japan
| | - Atsutaka Maeda
- Department of Basic Science, University of Tokyo, Meguro, Tokyo, 153-8902, Japan
| | - Kazunori Ueno
- Department of Basic Science, University of Tokyo, Meguro, Tokyo, 153-8902, Japan.
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26
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Krzton-Maziopa A, Pesko E, Puzniak R. Superconducting selenides intercalated with organic molecules: synthesis, crystal structure, electric and magnetic properties, superconducting properties, and phase separation in iron based-chalcogenides and hybrid organic-inorganic superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:243001. [PMID: 29664412 DOI: 10.1088/1361-648x/aabeb5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Layered iron-based superconducting chalcogenides intercalated with molecular species are the subject of intensive studies, especially in the field of solid state chemistry and condensed matter physics, because of their intriguing chemistry and tunable electric and magnetic properties. Considerable progress in the research, revealing superconducting inorganic-organic hybrid materials with transition temperatures to superconducting state, T c, up to 46 K, has been brought in recent years. These novel materials are synthesized by low-temperature intercalation of molecular species, such as solvates of alkali metals and nitrogen-containing donor compounds, into layered FeSe-type structure. Both the chemical nature as well as orientation of organic molecules between the layers of inorganic host, play an important role in structural modifications and may be used for fine tuning of superconducting properties. Furthermore, a variety of donor species compatible with alkali metals, as well as the possibility of doping also in the host structure (either on Fe or Se sites), makes this system quite flexible and gives a vast array of new materials with tunable electric and magnetic properties. In this review, the main aspects of intercalation chemistry are discussed with a particular attention paid to the influence of the unique nature of intercalating species on the crystal structure and physical properties of the hybrid inorganic-organic materials. To get a full picture of these materials, a comprehensive description of the most effective chemical and electrochemical methods, utilized for synthesis of intercalated species, with critical evaluation of their strong and weak points, related to feasibility of synthesis, phase purity, crystal size and morphology of final products, is included as well.
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Affiliation(s)
- Anna Krzton-Maziopa
- Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, PL-00-664 Warsaw, Poland
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27
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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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28
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Wang Z, Liu C, Liu Y, Wang J. High-temperature superconductivity in one-unit-cell FeSe films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:153001. [PMID: 28176680 DOI: 10.1088/1361-648x/aa5f26] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Since the dramatic enhancement of the superconducting transition temperature (T c) was reported in a one-unit-cell FeSe film grown on a SrTiO3 substrate (1-UC FeSe/STO) by molecular beam epitaxy (MBE), related research on this system has become a new frontier in condensed matter physics. In this paper, we present a brief review on this rapidly developing field, mainly focusing on the superconducting properties of 1-UC FeSe/STO. Experimental evidence for high-temperature superconductivity in 1-UC FeSe/STO, including direct evidence revealed by transport and diamagnetic measurements, as well as other evidence from scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES), are overviewed. The potential mechanisms of the enhanced superconductivity are also discussed. There are accumulating arguments to suggest that the strengthened Cooper pairing in 1-UC FeSe/STO originates from the interface effects, specifically the charge transfer and coupling to phonon modes in the TiO2 plane. The study of superconductivity in 1-UC FeSe/STO not only sheds new light on the mechanism of high-temperature superconductors with layered structures, but also provides an insight into the exploration of new superconductors by interface engineering.
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Affiliation(s)
- Ziqiao Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
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29
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Xu M, Song X, Wang H. Substrate and band bending effects on monolayer FeSe on SrTiO 3(001). Phys Chem Chem Phys 2017; 19:7964-7970. [PMID: 28262868 DOI: 10.1039/c7cp00173h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Motivated by the high superconducting transition temperature (TC) shown by monolayer FeSe on cubic perovskite SrTiO3(001) and SrTiO3(001)-2×1 reconstructed surfaces, in this study, we explore the atomic and electronic structures of monolayer FeSe on various SrTiO3(001)-2×1 surface reconstructions using the CALYPSO method and first-principles calculations. Our search reveals two new Ti2O2 and Ti2O reconstructed surface structures, besides the Ti2O3 and double TiO2 layer reconstructed surfaces, and the two new Ti2O2 and Ti2O reconstructed surface structures are more stable under Ti-rich conditions than under Ti-poor conditions. The Fermi-surface topology of an FeSe monolayer on Ti2O3- and Ti2O2-type reconstructed STO surfaces is different from that of an FeSe monolayer on a Ti2O-type STO reconstructed surface. The established structure of monolayer FeSe on a Ti2O-type STO(001) reconstructed surface can naturally explain the experimental observation of the electronic band structure on the monolayer FeSe superconductor and obtained electrons counting per Fe atom. Surface states in the mid-gap induced by various STO surface reconstructions will result in band bending. The surface-state-induced band bending is also responsible for the electron transfer from the STO substrate to the FeSe films.
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Affiliation(s)
- Meiling Xu
- State Key Lab of Superhard Materials, Jilin University, Changchun 130023, China. and Beijing Computational Science Research Center, Beijing 100084, China
| | - Xianqi Song
- State Key Lab of Superhard Materials, Jilin University, Changchun 130023, China.
| | - Hui Wang
- State Key Lab of Superhard Materials, Jilin University, Changchun 130023, China.
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30
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Manna S, Kamlapure A, Cornils L, Hänke T, Hedegaard EMJ, Bremholm M, Iversen BB, Hofmann P, Wiebe J, Wiesendanger R. Interfacial superconductivity in a bi-collinear antiferromagnetically ordered FeTe monolayer on a topological insulator. Nat Commun 2017; 8:14074. [PMID: 28094258 PMCID: PMC5247605 DOI: 10.1038/ncomms14074] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 11/25/2016] [Indexed: 11/09/2022] Open
Abstract
The discovery of high-temperature superconductivity in Fe-based compounds triggered numerous investigations on the interplay between superconductivity and magnetism, and on the enhancement of transition temperatures through interface effects. It is widely believed that the emergence of optimal superconductivity is intimately linked to the suppression of long-range antiferromagnetic (AFM) order, although the exact microscopic picture remains elusive because of the lack of atomically resolved data. Here we present spin-polarized scanning tunnelling spectroscopy of ultrathin FeTe1-xSex (x=0, 0.5) films on bulk topological insulators. Surprisingly, we find an energy gap at the Fermi level, indicating superconducting correlations up to Tc∼6 K for one unit cell FeTe grown on Bi2Te3, in contrast to the non-superconducting bulk FeTe. The gap spatially coexists with bi-collinear AFM order. This finding opens perspectives for theoretical studies of competing orders in Fe-based superconductors and for experimental investigations of exotic phases in superconducting layers on topological insulators.
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Affiliation(s)
- S Manna
- Department of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
| | - A Kamlapure
- Department of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
| | - L Cornils
- Department of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
| | - T Hänke
- Department of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
| | - E M J Hedegaard
- Department of Chemistry and iNANO, Center for Materials Crystallography, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - M Bremholm
- Department of Chemistry and iNANO, Center for Materials Crystallography, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - B B Iversen
- Department of Chemistry and iNANO, Center for Materials Crystallography, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Ph Hofmann
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, DK-8000 Aarhus C, Denmark
| | - J Wiebe
- Department of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
| | - R Wiesendanger
- Department of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
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31
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Kang J, Fernandes RM. Superconductivity in FeSe Thin Films Driven by the Interplay between Nematic Fluctuations and Spin-Orbit Coupling. PHYSICAL REVIEW LETTERS 2016; 117:217003. [PMID: 27911515 DOI: 10.1103/physrevlett.117.217003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Indexed: 06/06/2023]
Abstract
The origin of the high-temperature superconducting state observed in FeSe thin films, whose phase diagram displays no sign of magnetic order, remains a hotly debated topic. Here we investigate whether fluctuations arising due to the proximity to a nematic phase, which is observed in the phase diagram of this material, can promote superconductivity. We find that nematic fluctuations alone promote a highly degenerate pairing state, in which both s-wave and d-wave symmetries are equally favored, and T_{c} is consequently suppressed. However, the presence of a sizable spin-orbit coupling or inversion symmetry breaking at the film interface lifts this harmful degeneracy and selects the s-wave state, in agreement with recent experimental proposals. The resulting gap function displays a weak anisotropy, which agrees with experiments in monolayer FeSe and intercalated Li_{1-x}(OH)_{x}FeSe.
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Affiliation(s)
- Jian Kang
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Rafael M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
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32
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Liu Y, Wang G, Ying T, Lai X, Jin S, Liu N, Hu J, Chen X. Understanding Doping, Vacancy, Lattice Stability, and Superconductivity in K x Fe 2-y Se 2. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2016; 3:1600098. [PMID: 27840799 PMCID: PMC5096254 DOI: 10.1002/advs.201600098] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 04/19/2016] [Indexed: 06/06/2023]
Abstract
Metal-intercalated iron selenides are a class of superconductors that have received much attention but are less understood in comparison with their FeAs-based counterparts. Here, the controversial issues such as Fe vacancy, the real phase responsible for superconductivity, and lattice stability have been addressed based on first-principles calculations. New insights into the distinct features in terms of carrier doping have been revealed.
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Affiliation(s)
- Yu Liu
- Research and Development Center for Functional CrystalsBeijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing100190P.R. China
| | - Gang Wang
- Research and Development Center for Functional CrystalsBeijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing100190P.R. China
| | - Tianping Ying
- Research and Development Center for Functional CrystalsBeijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing100190P.R. China
| | - Xiaofang Lai
- Research and Development Center for Functional CrystalsBeijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing100190P.R. China
| | - Shifeng Jin
- Research and Development Center for Functional CrystalsBeijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing100190P.R. China
| | - Ning Liu
- Research and Development Center for Functional CrystalsBeijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing100190P.R. China
| | - Jiangping Hu
- Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing100190P.R. China
- Collaborative Innovation Center of Quantum MatterBeijingP.R. China
| | - Xiaolong Chen
- Research and Development Center for Functional CrystalsBeijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing100190P.R. China
- Collaborative Innovation Center of Quantum MatterBeijingP.R. China
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33
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Liu HC, Li H, He QL, Sou IK, Goh SK, Wang J. Robust two-dimensional superconductivity and vortex system in Bi2Te3/FeTe heterostructures. Sci Rep 2016; 6:26168. [PMID: 27185305 PMCID: PMC4868974 DOI: 10.1038/srep26168] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 04/27/2016] [Indexed: 11/09/2022] Open
Abstract
The discovery of two-dimensional superconductivity in Bi2Te3/FeTe heterostructures provides a new platform for the search of Majorana fermions in condensed matter systems. Since Majorana fermions are expected to reside at the core of the vortices, a close examination of the vortex dynamics in superconducting interface is of paramount importance. Here, we report the robustness of the interfacial superconductivity and 2D vortex dynamics in four as-grown and aged Bi2Te3/FeTe heterostructure with different Bi2Te3 epilayer thickness (3, 5, 7, 14 nm). After two years' air exposure, superconductivity remains robust even when the thickness of Bi2Te3 epilayer is down to 3 nm. Meanwhile, a new feature at ~13 K is induced in the aged samples, and the high field studies reveal its relevance to superconductivity. The resistance of all as-grown and aged heterostructures, just below the superconducting transition temperature follows the Arrhenius relation, indicating the thermally activated flux flow behavior at the interface of Bi2Te3 and FeTe. Moreover, the activation energy exhibits a logarithmic dependence on the magnetic field, providing a compelling evidence for the 2D vortex dynamics in this novel system. The weak disorder associated with aging-induced Te vacancies is possibly responsible for these observed phenomena.
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Affiliation(s)
- Hong-Chao Liu
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
- Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Hui Li
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Qing Lin He
- William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Iam Keong Sou
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
- William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Swee K. Goh
- Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Jiannong Wang
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
- William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
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34
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Lei B, Cui JH, Xiang ZJ, Shang C, Wang NZ, Ye GJ, Luo XG, Wu T, Sun Z, Chen XH. Evolution of High-Temperature Superconductivity from a Low-T_{c} Phase Tuned by Carrier Concentration in FeSe Thin Flakes. PHYSICAL REVIEW LETTERS 2016; 116:077002. [PMID: 26943553 DOI: 10.1103/physrevlett.116.077002] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Indexed: 05/05/2023]
Abstract
We report the evolution of superconductivity in an FeSe thin flake with systematically regulated carrier concentrations by the liquid-gating technique. With electron doping tuned by the gate voltage, high-temperature superconductivity with an onset at 48 K can be achieved in an FeSe thin flake with T_{c} less than 10 K. This is the first time such high temperature superconductivity in FeSe is achieved without either an epitaxial interface or external pressure, and it definitely proves that the simple electron-doping process is able to induce high-temperature superconductivity with T_{c}^{onset} as high as 48 K in bulk FeSe. Intriguingly, our data also indicate that the superconductivity is suddenly changed from a low-T_{c} phase to a high-T_{c} phase with a Lifshitz transition at a certain carrier concentration. These results help to build a unified picture to understand the high-temperature superconductivity among all FeSe-derived superconductors and shed light on the further pursuit of a higher T_{c} in these materials.
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Affiliation(s)
- B Lei
- Hefei National Laboratory for Physical Science at 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 H Cui
- Hefei National Laboratory for Physical Science at 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
| | - Z J Xiang
- Hefei National Laboratory for Physical Science at 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
| | - C Shang
- Hefei National Laboratory for Physical Science at 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
| | - N Z Wang
- Hefei National Laboratory for Physical Science at 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
| | - G J Ye
- Hefei National Laboratory for Physical Science at 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
| | - X G Luo
- Hefei National Laboratory for Physical Science at 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
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - T Wu
- Hefei National Laboratory for Physical Science at 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
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Z Sun
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - X H Chen
- Hefei National Laboratory for Physical Science at 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
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui 230031, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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Vasconcelos HMDN, Eddrief M, Zheng Y, Demaille D, Hidki S, Fonda E, Novikova A, Fujii J, Torelli P, Salles BR, Vobornik I, Panaccione G, de Oliveira AJA, Marangolo M, Vidal F. Magnetically Hard Fe3Se4 Embedded in Bi2Se3 Topological Insulator Thin Films Grown by Molecular Beam Epitaxy. ACS NANO 2016; 10:1132-1138. [PMID: 26653134 DOI: 10.1021/acsnano.5b06430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We investigated the structural, magnetic, and electronic properties of Bi2Se3 epilayers containing Fe grown on GaAs(111) by molecular beam epitaxy. It is shown that, in the window of growth parameters leading to Bi2Se3 epilayers with optimized quality, Fe atom clustering leads to the formation of FexSey inclusions. These objects have platelet shape and are embedded within Bi2Se3. Monoclinic Fe3Se4 is identified as the main secondary phase through detailed structural measurements. Due to the presence of the hard ferrimagnetic Fe3Se4 inclusions, the system exhibits a very large coercive field at low temperature and room temperature magnetic ordering. Despite this composite structure and the proximity of a magnetic phase, the surface electronic structure of Bi2Se3 is preserved, as shown by the persistence of a gapless Dirac cone at Γ.
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Affiliation(s)
- Hugo Menezes do Nascimento Vasconcelos
- Sorbonne Universités , UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris, France
- Departamento de Física, Universidade Federal de São Carlos , CP 676, 13565-905 São Carlos, SP, Brazil
| | - Mahmoud Eddrief
- Sorbonne Universités , UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris, France
| | - Yunlin Zheng
- Sorbonne Universités , UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris, France
| | - Dominique Demaille
- Sorbonne Universités , UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris, France
| | - Sarah Hidki
- Sorbonne Universités , UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris, France
| | - Emiliano Fonda
- Synchrotron Soleil , L'Orme des Merisiers Saint-Aubin BP 48, 91192 Gif-sur-Yvette Cedex, France
| | - Anastasiia Novikova
- Synchrotron Soleil , L'Orme des Merisiers Saint-Aubin BP 48, 91192 Gif-sur-Yvette Cedex, France
| | - Jun Fujii
- Istituto Officina dei Materiali (IOM) - CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
| | - Piero Torelli
- Istituto Officina dei Materiali (IOM) - CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
| | - Benjamin Rache Salles
- Istituto Officina dei Materiali (IOM) - CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
- Instituto de Física, Universidade Federal do Rio de Janeiro , 21941-972 Rio de Janeiro, RJ, Brazil
| | - Ivana Vobornik
- Istituto Officina dei Materiali (IOM) - CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
| | - Giancarlo Panaccione
- Istituto Officina dei Materiali (IOM) - CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
| | | | - Massimiliano Marangolo
- Sorbonne Universités , UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris, France
| | - Franck Vidal
- Sorbonne Universités , UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris, France
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Miyata Y, Nakayama K, Sugawara K, Sato T, Takahashi T. High-temperature superconductivity in potassium-coated multilayer FeSe thin films. NATURE MATERIALS 2015; 14:775-779. [PMID: 26030306 DOI: 10.1038/nmat4302] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 04/21/2015] [Indexed: 06/04/2023]
Abstract
The recent discovery of possible high-temperature (T(c)) superconductivity over 65 K in a monolayer FeSe film on SrTiO3 (refs 1-6) triggered a fierce debate on how superconductivity evolves from bulk to film, because bulk FeSe crystal exhibits a T(c) of no higher than 10 K (ref. 7). However, the difficulty in controlling the carrier density and the number of FeSe layers has hindered elucidation of this problem. Here, we demonstrate that deposition of potassium onto FeSe films markedly expands the accessible doping range towards the heavily electron-doped region. Intriguingly, we have succeeded in converting non-superconducting films with various thicknesses into superconductors with T(c) as high as 48 K. We also found a marked increase in the magnitude of the superconducting gap on decreasing the FeSe film thickness, indicating that the interface plays a crucial role in realizing the high-temperature superconductivity. The results presented provide a new strategy to enhance and optimize T(c) in ultrathin films of iron-based superconductors.
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Affiliation(s)
- Y Miyata
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - K Nakayama
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - K Sugawara
- WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - T Sato
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | - T Takahashi
- 1] Department of Physics, Tohoku University, Sendai 980-8578, Japan [2] WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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Xie Y, Cao HY, Zhou Y, Chen S, Xiang H, Gong XG. Oxygen Vacancy Induced Flat Phonon Mode at FeSe /SrTiO3 interface. Sci Rep 2015; 5:10011. [PMID: 26067548 PMCID: PMC4464289 DOI: 10.1038/srep10011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 03/25/2015] [Indexed: 11/09/2022] Open
Abstract
A high-frequency optical phonon mode of SrTiO3 (STO) was found to assist the high-temperature superconductivity observed recently at the interface between monolayer FeSe and STO substrate. However, the origin of this mode is not clear. Through first-principles calculations, we find that there is a novel polar phonon mode on the surface layers of the STO substrate, which does not exist in the STO crystals. The oxygen vacancies near the FeSe/STO interface drives the dispersion of this phonon mode to be flat and lowers its energy, whereas the charge transfer between STO substrate and FeSe monolayer further reduces its energy to 81 meV. This energy is in good agreement with the experimental value fitted by Lee et al. for the phonon mode responsible for the observed replica band separations and the increased superconducting gap. The oxygen-vacancy-induced flat and polar phonon mode provides clues for understanding the origin of high Tc superconductivity at the FeSe/STO interface.
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Affiliation(s)
- Yun Xie
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (MOE), Collaborative Innovation Center of Advanced Microstructure, Department of Physics, Fudan University, Shanghai 200433, China
| | - Hai-Yuan Cao
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (MOE), Collaborative Innovation Center of Advanced Microstructure, Department of Physics, Fudan University, Shanghai 200433, China
| | - Yang Zhou
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (MOE), Collaborative Innovation Center of Advanced Microstructure, Department of Physics, Fudan University, Shanghai 200433, China
| | - Shiyou Chen
- Key Laboratory of Polar Materials and Devices (MOE), East China Normal University, Shanghai 200241, China
| | - Hongjun Xiang
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (MOE), Collaborative Innovation Center of Advanced Microstructure, Department of Physics, Fudan University, Shanghai 200433, China
| | - Xin-Gao Gong
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (MOE), Collaborative Innovation Center of Advanced Microstructure, Department of Physics, Fudan University, Shanghai 200433, China
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38
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Liu X, Zhao L, He S, He J, Liu D, Mou D, Shen B, Hu Y, Huang J, Zhou XJ. Electronic structure and superconductivity of FeSe-related superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:183201. [PMID: 25879999 DOI: 10.1088/0953-8984/27/18/183201] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
FeSe superconductors and their related systems have attracted much attention in the study of iron-based superconductors owing to their simple crystal structure and peculiar electronic and physical properties. The bulk FeSe superconductor has a superconducting transition temperature (Tc) of ~8 K and it can be dramatically enhanced to 37 K at high pressure. On the other hand, its cousin system, FeTe, possesses a unique antiferromagnetic ground state but is non-superconducting. Substitution of Se with Te in the FeSe superconductor results in an enhancement of Tc up to 14.5 K and superconductivity can persist over a large composition range in the Fe(Se,Te) system. Intercalation of the FeSe superconductor leads to the discovery of the AxFe2-ySe2 (A = K, Cs and Tl) system that exhibits a Tc higher than 30 K and a unique electronic structure of the superconducting phase. A recent report of possible high temperature superconductivity in single-layer FeSe/SrTiO3 films with a Tc above 65 K has generated much excitement in the community. This pioneering work opens a door for interface superconductivity to explore for high Tc superconductors. The distinct electronic structure and superconducting gap, layer-dependent behavior and insulator-superconductor transition of the FeSe/SrTiO3 films provide critical information in understanding the superconductivity mechanism of iron-based superconductors. In this paper, we present a brief review of the investigation of the electronic structure and superconductivity of the FeSe superconductor and related systems, with a particular focus on the FeSe films.
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Affiliation(s)
- Xu Liu
- National Lab for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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Hayashi F, Lei H, Guo J, Hosono H. Modulation Effect of Interlayer Spacing on the Superconductivity of Electron-Doped FeSe-Based Intercalates. Inorg Chem 2015; 54:3346-51. [DOI: 10.1021/ic503033k] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Fumitaka Hayashi
- Frontier
Research Center, Tokyo Institute of Technology, 4259-S2-13 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Hechang Lei
- Frontier
Research Center, Tokyo Institute of Technology, 4259-S2-13 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Jiangang Guo
- Frontier
Research Center, Tokyo Institute of Technology, 4259-S2-13 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Hideo Hosono
- Frontier
Research Center, Tokyo Institute of Technology, 4259-S2-13 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
- Materials
Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
- Materials
and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
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40
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Ge JF, Liu ZL, Liu C, Gao CL, Qian D, Xue QK, Liu Y, Jia JF. Superconductivity above 100 K in single-layer FeSe films on doped SrTiO3. NATURE MATERIALS 2015; 14:285-9. [PMID: 25419814 DOI: 10.1038/nmat4153] [Citation(s) in RCA: 280] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 10/30/2014] [Indexed: 05/05/2023]
Abstract
Recent experiments on FeSe films grown on SrTiO3 (STO) suggest that interface effects can be used as a means to reach superconducting critical temperatures (Tc) of up to 80 K (ref. ). This is nearly ten times the Tc of bulk FeSe and higher than the record value of 56 K for known bulk Fe-based superconductors. Together with recent studies of superconductivity at oxide heterostructure interfaces, these results rekindle the long-standing idea that electron pairing at interfaces between two different materials can be tailored to achieve high-temperature superconductivity. Subsequent angle-resolved photoemission spectroscopy measurements of the FeSe/STO system revealed an electronic structure distinct from bulk FeSe (refs , ), with an energy gap vanishing at around 65 K. However, ex situ electrical transport measurements have so far detected zero resistance-the key experimental signature of superconductivity-only below 30 K. Here, we report the observation of superconductivity with Tc above 100 K in the FeSe/STO system by means of in situ four-point probe electrical transport measurements. This finding confirms FeSe/STO as an ideal material for studying high-Tc superconductivity.
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Affiliation(s)
- Jian-Feng Ge
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road Shanghai 200240, China
| | - Zhi-Long Liu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road Shanghai 200240, China
| | - Canhua Liu
- 1] Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road Shanghai 200240, China [2] Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - Chun-Lei Gao
- 1] Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road Shanghai 200240, China [2] Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - Dong Qian
- 1] Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road Shanghai 200240, China [2] Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - Qi-Kun Xue
- Department of Physics, Tsinghua University, Beijing 100084, China
| | - Ying Liu
- 1] Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road Shanghai 200240, China [2] Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China [3] Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Jin-Feng Jia
- 1] Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road Shanghai 200240, China [2] Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
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Schneider R, Zaitsev AG, Fuchs D, von Löhneysen H. Excess conductivity and Berezinskii-Kosterlitz-Thouless transition in superconducting FeSe thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:455701. [PMID: 25319094 DOI: 10.1088/0953-8984/26/45/455701] [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
Temperature-dependent electronic transport in the vicinity of the superconducting transition is reported for quasi-two-dimensional textured FeSe thin films. The conspicuous rounding of the resistive transitions and large transition widths are indications of excess conductivity due to thermal Cooper-pair fluctuations, which can be well-described by the two-dimensional Aslamazov-Larkin theory. The Halperin-Nelson form of the sheet resistance between the phase-ordering temperature TBKT and the mean-field temperature TMF, and the power-law behaviour of the voltage-current characteristics, with a distinctive jump of the exponent at TBKT, are indicative of a Berezinskii-Kosterlitz-Thouless transition. The complementary results suggest a two-dimensional character of superconductivity in the FeSe films and allow a quantitative estimate of the Ginzburg number Gi.
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Affiliation(s)
- R Schneider
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, D-76021 Karlsruhe, Germany
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