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Hu LH, Zhang RX. Dislocation Majorana bound states in iron-based superconductors. Nat Commun 2024; 15:2337. [PMID: 38491015 PMCID: PMC10943028 DOI: 10.1038/s41467-024-46618-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Accepted: 03/04/2024] [Indexed: 03/18/2024] Open
Abstract
We show that lattice dislocations of topological iron-based superconductors such as FeTe1-xSex will intrinsically trap non-Abelian Majorana quasiparticles, in the absence of any external magnetic field. Our theory is motivated by the recent experimental observations of normal-state weak topology and surface magnetism that coexist with superconductivity in FeTe1-xSex, the combination of which naturally achieves an emergent second-order topological superconductivity in a two-dimensional subsystem spanned by screw or edge dislocations. This exemplifies a new embedded higher-order topological phase in class D, where Majorana zero modes appear around the "corners" of a low-dimensional embedded subsystem, instead of those of the full crystal. A nested domain wall theory is developed to understand the origin of these defect Majorana zero modes. When the surface magnetism is absent, we further find that s± pairing symmetry itself is capable of inducing a different type of class-DIII embedded higher-order topology with defect-bound Majorana Kramers pairs. We also provide detailed discussions on the real-world material candidates for our proposals, including FeTe1-xSex, LiFeAs, β-PdBi2, and heterostructures of bismuth, etc. Our work establishes lattice defects as a new venue to achieve high-temperature topological quantum information processing.
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Affiliation(s)
- Lun-Hui Hu
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, USA
- Institute for Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, TN, USA
- Center for Correlated Matter and School of Physics, Zhejiang University, Hangzhou, China
| | - Rui-Xing Zhang
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, USA.
- Institute for Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, TN, USA.
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, USA.
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2
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Chiu CK, Wang Z. Yu-Shiba-Rusinov States in a Superconductor with Topological Z_{2} Bands. PHYSICAL REVIEW LETTERS 2022; 128:237001. [PMID: 35749202 DOI: 10.1103/physrevlett.128.237001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 04/19/2022] [Accepted: 04/26/2022] [Indexed: 06/15/2023]
Abstract
A Yu-Shiba-Rusinov (YSR) state is a localized in-gap state induced by a magnetic impurity in a superconductor. Recent experiments used an STM tip to manipulate the exchange coupling between an Fe adatom and the FeTe_{0.55}Se_{0.45} superconductor possessing a Z_{2} nontrivial band structure with topological surface states. As the tip moves close to the single Fe adatom, the energy of the in-gap state modulates and exhibits a zero-energy crossing followed by an unusual return to zero energy, which cannot be understood by coupling the magnetic impurity to the superconducting topological surface Dirac cone. Here, we numerically and analytically study the YSR states in superconductors with nontrivial Z_{2} bands and show the emergence of the two zero-energy crossings as a function of the exchange coupling between the magnetic impurity and the bulk states. We analyze the role of the topological surface states and compare in-gap states to systems with trivial Z_{2} bands. The spin polarization of the YSR states is further studied for future experimental measurement.
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Affiliation(s)
- Ching-Kai Chiu
- RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), Wako, Saitama 351-0198, Japan
- Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Ziqiang Wang
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
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3
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Jiang D, Pan Y, Wang S, Lin Y, Holland CM, Kirtley JR, Chen X, Zhao J, Chen L, Yin S, Wang Y. Observation of robust edge superconductivity in Fe(Se,Te) under strong magnetic perturbation. Sci Bull (Beijing) 2021; 66:425-432. [PMID: 36654179 DOI: 10.1016/j.scib.2020.10.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 09/04/2020] [Accepted: 09/29/2020] [Indexed: 01/20/2023]
Abstract
The iron-chalcogenide high temperature superconductor Fe(Se,Te) (FST) has been reported to exhibit complex magnetic ordering and nontrivial band topology which may lead to novel superconducting phenomena. However, the recent studies have so far been largely concentrated on its band and spin structures while its mesoscopic electronic and magnetic response, crucial for future device applications, has not been explored experimentally. Here, we used scanning superconducting quantum interference device microscopy for its sensitivity to both local diamagnetic susceptibility and current distribution in order to image the superfluid density and supercurrent in FST. We found that in FST with 10% interstitial Fe, whose magnetic structure was heavily disrupted, bulk superconductivity was significantly suppressed whereas edge still preserved strong superconducting diamagnetism. The edge dominantly carried supercurrent despite of a very long magnetic penetration depth. The temperature dependences of the superfluid density and supercurrent distribution were distinctively different between the edge and the bulk. Our Heisenberg modeling showed that magnetic dopants stabilize anti-ferromagnetic spin correlation along the edge, which may contribute towards its robust superconductivity. Our observations hold implication for FST as potential platforms for topological quantum computation and superconducting spintronics.
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Affiliation(s)
- Da Jiang
- Shanghai Institute of Microsystem and Information Technology, Shanghai 200050, China.
| | - Yinping Pan
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Shiyuan Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yishi Lin
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Connor M Holland
- Department of Physics, Stanford University, Stanford, CA 94305, USA
| | - John R Kirtley
- Department of Physics, Stanford University, Stanford, CA 94305, USA
| | - Xianhui Chen
- Department of Physics, University of Science and Technology of China, Hefei 230026, China
| | - Jun Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Lei Chen
- Shanghai Institute of Microsystem and Information Technology, Shanghai 200050, China
| | - Shaoyu Yin
- Institute for Theoretical Physics and Cosmology, Zhejiang University of Technology, Hangzhou 310023, China; State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
| | - Yihua Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China.
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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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5
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Chen W, Gentile T, Ye Q, Kirchhoff A, Watson S, Rodriguez-Rivera J, Qiu Y, Broholm C. Recent advancements of wide-angle polarization analysis with3He neutron spin filters. ACTA ACUST UNITED AC 2016. [DOI: 10.1088/1742-6596/746/1/012016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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6
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Influence of interstitial Fe to the phase diagram of Fe1+yTe1-xSex single crystals. Sci Rep 2016; 6:32290. [PMID: 27577047 PMCID: PMC5006070 DOI: 10.1038/srep32290] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 08/04/2016] [Indexed: 11/09/2022] Open
Abstract
Superconductivity (SC) with the suppression of long-range antiferromagnetic (AFM) order is observed in the parent compounds of both iron-based and cuprate superconductors. The AFM wave vectors are bicollinear (π, 0) in the parent compound FeTe different from the collinear AFM order (π, π) in most iron pnictides. Study of the phase diagram of Fe1+yTe1-xSex is the most direct way to investigate the competition between bicollinear AFM and SC. However, presence of interstitial Fe affects both magnetism and SC of Fe1+yTe1-xSex, which hinders the establishment of the real phase diagram. Here, we report the comparison of doping-temperature (x-T) phase diagrams for Fe1+yTe1-xSex (0 ≤ x ≤ 0.43) single crystals before and after removing interstitial Fe. Without interstitial Fe, the AFM state survives only for x < 0.05, and bulk SC emerges from x = 0.05, and does not coexist with the AFM state. The previously reported spin glass state, and the coexistence of AFM and SC may be originated from the effect of the interstitial Fe. The phase diagram of Fe1+yTe1-xSex is found to be similar to the case of the "1111" system such as LaFeAsO1-xFx, and is different from that of the "122" system.
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Spin-liquid polymorphism in a correlated electron system on the threshold of superconductivity. Proc Natl Acad Sci U S A 2015; 112:10316-20. [PMID: 26240327 DOI: 10.1073/pnas.1503559112] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report neutron scattering measurements which reveal spin-liquid polymorphism in an "11" iron chalcogenide superconductor. It occurs when a poorly metallic magnetic state of FeTe is tuned toward superconductivity by substitution of a small amount of tellurium with isoelectronic sulfur. We observe a liquid-like magnetic response, which is described by the coexistence of two disordered magnetic phases with different local structures whose relative abundance depends on temperature. One is the ferromagnetic (FM) plaquette phase observed in undoped, nonsuperconducting FeTe, which preserves the C4 symmetry of the underlying square lattice and is favored at high temperatures, whereas the other is the antiferromagnetic plaquette phase with broken C4 symmetry, which emerges with doping and is predominant at low temperatures. These findings suggest the coexistence of and competition between two distinct liquid states, and a liquid-liquid phase transformation between these states, in the electronic spin system of FeTe(1-x)(S,Se)(x). We have thus discovered the remarkable physics of competing spin-liquid polymorphs in a correlated electron system approaching superconductivity. Our results facilitate an understanding of large swaths of recent experimental data in unconventional superconductors. In particular, the phase with lower C2 local symmetry, whose emergence precedes superconductivity, naturally accounts for a propensity for forming electronic nematic states which have been observed experimentally, in cuprate and iron-based superconductors alike.
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Bao W. Structure, magnetic order and excitations in the 245 family of Fe-based superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:023201. [PMID: 25427222 DOI: 10.1088/0953-8984/27/2/023201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Elastic neutron scattering simultaneously probes both the crystal structure and magnetic order in a material. Inelastic neutron scattering measures phonons and magnetic excitations. Here, we review the average composition, crystal structure and magnetic order in the 245 family of Fe-based superconductors and in related insulating compounds from neutron diffraction works. A three-dimensional phase-diagram summarizes various structural, magnetic and electronic properties as a function of the sample composition. A high pressure phase diagram for the superconductor is also provided. Magnetic excitations and the theoretic Heisenberg Hamiltonian are provided for the superconductor. Issues for future works are discussed.
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Affiliation(s)
- Wei Bao
- Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
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Gastiasoro MN, Andersen BM. Enhancement of magnetic stripe order in iron-pnictide superconductors from the interaction between conduction electrons and magnetic impurities. PHYSICAL REVIEW LETTERS 2014; 113:067002. [PMID: 25148344 DOI: 10.1103/physrevlett.113.067002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Indexed: 06/03/2023]
Abstract
Recent experimental studies have revealed several unexpected properties of Mn-doped BaFe(2)As(2). These include extension of the stripelike magnetic (π,0) phase to high temperatures above a critical Mn concentration only, the presence of diffusive and weakly temperature dependent magnetic (π,π) checkerboard scattering, and an apparent absent structural distortion from tetragonal to orthorhombic symmetry. Here, we study the effects of magnetic impurities both below and above the Néel transition temperature within a real-space five-band model appropriate to the iron pnictides. We show how these experimental findings can be explained by a cooperative behavior of the magnetic impurities and the conduction electrons mediating the Ruderman-Kittel-Kasuya-Yosida interactions between them.
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Affiliation(s)
- Maria N Gastiasoro
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Brian M Andersen
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
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Chen WC, Gentile TR, Erwin R, Watson S, Ye Q, Krycka KL, Maranville BB. 3He spin filter based polarized neutron capability at the NIST Center for Neutron Research. ACTA ACUST UNITED AC 2014. [DOI: 10.1088/1742-6596/528/1/012014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Fobes D, Zaliznyak IA, Xu Z, Zhong R, Gu G, Tranquada JM, Harriger L, Singh D, Garlea VO, Lumsden M, Winn B. Ferro-orbital ordering transition in iron telluride Fe(1+y)Te. PHYSICAL REVIEW LETTERS 2014; 112:187202. [PMID: 24856717 DOI: 10.1103/physrevlett.112.187202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Indexed: 06/03/2023]
Abstract
Fe(1+y)Te with y≲0.05 exhibits a first-order phase transition on cooling to a state with a lowered structural symmetry, bicollinear antiferromagnetic order, and metallic conductivity, dρ/dT>0. Here, we study samples with y=0.09(1), where the frustration effects of the interstitial Fe decouple different orders, leading to a sequence of transitions. While the lattice distortion is closely followed by incommensurate magnetic order, the development of bicollinear order and metallic electronic coherence is uniquely associated with a separate hysteretic first-order transition, at a markedly lower temperature, to a phase with dramatically enhanced bond-order wave (BOW) order. The BOW state suggests ferro-orbital ordering, where electronic delocalization in ferromagnetic zigzag chains decreases local spin and results in metallic transport.
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Affiliation(s)
- David Fobes
- CMPMSD, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Igor A Zaliznyak
- CMPMSD, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Zhijun Xu
- CMPMSD, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Ruidan Zhong
- CMPMSD, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Genda Gu
- CMPMSD, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - John M Tranquada
- CMPMSD, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Leland Harriger
- NCNR, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Deepak Singh
- NCNR, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - V Ovidiu Garlea
- QCMD, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Mark Lumsden
- QCMD, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Barry Winn
- QCMD, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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12
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Ye Q, Gentile T, Anderson J, Broholm C, Chen W, DeLand Z, Erwin R, Fu C, Fuller J, Kirchhoff A, Rodriguez-Rivera J, Thampy V, Walker T, Watson S. Wide Angle Polarization Analysis with Neutron Spin Filters. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/j.phpro.2013.03.197] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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13
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Singh DJ. Superconductivity and magnetism in 11-structure iron chalcogenides in relation to the iron pnictides. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2012; 13:054304. [PMID: 27877517 PMCID: PMC5099618 DOI: 10.1088/1468-6996/13/5/054304] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 10/29/2012] [Indexed: 06/03/2023]
Abstract
This is a review of the magnetism and superconductivity in '11'-type Fe chalcogenides, as compared to the Fe-pnictide materials. The chalcogenides show many differences from the pnictides, as might be anticipated from their very varied chemistries. These differences include stronger renormalizations that might imply stronger correlation effects as well as different magnetic ordering patterns. Nevertheless the superconducting state and mechanism for superconductivity are apparently similar for the two classes of materials. Unanswered questions and challenges to theory are emphasized.
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Affiliation(s)
- David Joseph Singh
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6056, USA
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