1
|
Wang SZ, Yu XQ, Wei LX, Wang L, Cheng QJ, Peng K, Cheng FJ, Liu Y, Li FS, Ma XC, Xue QK, Song CL. Quantum spin driven Yu-Shiba-Rusinov multiplets and fermion-parity-preserving phase transition in K 3C 60. Sci Bull (Beijing) 2024; 69:1392-1399. [PMID: 38594099 DOI: 10.1016/j.scib.2024.03.052] [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: 12/12/2023] [Revised: 02/07/2024] [Accepted: 03/22/2024] [Indexed: 04/11/2024]
Abstract
Magnetic impurities in superconductors are of increasing interest due to emergent Yu-Shiba-Rusinov (YSR) states and Majorana zero modes for fault-tolerant quantum computation. However, a direct relationship between the YSR multiple states and magnetic anisotropy splitting of quantum impurity spins remains poorly characterized. By using scanning tunneling microscopy, we systematically resolve individual transition-metal (Fe, Cr, and Ni) impurities induced YSR multiplets as well as their Zeeman effects in the K3C60 superconductor. The YSR multiplets show identical d orbital-like wave functions that are symmetry-mismatched to the threefold K3C60(1 1 1) host surface, breaking point-group symmetries of the spatial distribution of YSR bound states in real space. Remarkably, we identify an unprecedented fermion-parity-preserving quantum phase transition between ground states with opposite signs of the uniaxial magnetic anisotropy that can be manipulated by an external magnetic field. These findings can be readily understood in terms of anisotropy splitting of quantum impurity spins, and thus elucidate the intricate interplay between the magnetic anisotropy and YSR multiplets.
Collapse
Affiliation(s)
- Shu-Ze Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xue-Qing Yu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Li-Xuan Wei
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Li Wang
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Qiang-Jun Cheng
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Kun Peng
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Fang-Jun Cheng
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Yu Liu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Fang-Sen Li
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China.
| | - Xu-Cun Ma
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Frontier Science Center for Quantum Information, Beijing 100084, China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Frontier Science Center for Quantum Information, Beijing 100084, China; Beijing Academy of Quantum Information Sciences, Beijing 100193, China; Southern University of Science and Technology, Shenzhen 518055, China.
| | - Can-Li Song
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Frontier Science Center for Quantum Information, Beijing 100084, China.
| |
Collapse
|
2
|
Zhang T, Hu Y, Su W, Chen C, Wang X, Li D, Lu Z, Yang W, Zhang Q, Dong X, Wang R, Wang X, Feng D, Zhang T. Phase Shift and Magnetic Anisotropy Induced Field Splitting of Impurity States in (Li_{1-x}Fe_{x})OHFeSe Superconductor. PHYSICAL REVIEW LETTERS 2023; 130:206001. [PMID: 37267540 DOI: 10.1103/physrevlett.130.206001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 03/21/2023] [Accepted: 04/10/2023] [Indexed: 06/04/2023]
Abstract
Revealing the energy and spatial characteristics of impurity-induced states in superconductors is essential for understanding their mechanism and fabricating a new quantum state by manipulating impurities. Here, by using high-resolution scanning tunneling microscopy and spectroscopy, we investigate the spatial distribution and magnetic field response of the impurity states in (Li_{1-x}Fe_{x})OHFeSe. We detect two pairs of strong in-gap states on the "dumbbell-shaped" defects. They display damped oscillations with different phase shifts and a direct phase-energy correlation. These features have long been predicted for the classical Yu-Shiba-Rusinov (YSR) state and are demonstrated here with unprecedented resolution for the first time. Moreover, upon applying magnetic field, all in-gap state peaks remarkably split into two rather than shift, and the splitting strength is field orientation dependent. Via detailed numerical model calculations, we find such an anisotropic splitting behavior can be naturally induced by a high-spin impurity coupled to an anisotropic environment, highlighting how magnetic anisotropy affects the behavior of YSR states.
Collapse
Affiliation(s)
- Tianzhen Zhang
- Department of Physics, State Key Laboratory of Surface Physics and Advanced Material Laboratory, Fudan University, Shanghai 200438, China
| | - Yining Hu
- Department of Physics, State Key Laboratory of Surface Physics and Advanced Material Laboratory, Fudan University, Shanghai 200438, China
| | - Wei Su
- Beijing Computational Science Research Center, Beijing 100084, China
- College of Physics and Electronic Engineering, Center for Computational Sciences, Sichuan Normal University, Chengdu 610068, China
| | - Chen Chen
- Department of Physics, State Key Laboratory of Surface Physics and Advanced Material Laboratory, Fudan University, Shanghai 200438, China
| | - Xu Wang
- Department of Physics, State Key Laboratory of Surface Physics and Advanced Material Laboratory, Fudan University, Shanghai 200438, China
| | - Dong Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Zouyouwei Lu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wentao Yang
- Department of Physics, State Key Laboratory of Surface Physics and Advanced Material Laboratory, Fudan University, Shanghai 200438, China
| | - Qingle Zhang
- Department of Physics, State Key Laboratory of Surface Physics and Advanced Material Laboratory, Fudan University, Shanghai 200438, China
| | - Xiaoli Dong
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Rui Wang
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center for Advanced Microstructures, Nanjing 210093, China
| | - Xiaoqun Wang
- School of Physics, Zhejiang University, Hangzhou 310058 Zhejiang, China
| | - Donglai Feng
- Department of Physics, State Key Laboratory of Surface Physics and Advanced Material Laboratory, Fudan University, Shanghai 200438, China
- National Synchrotron Radiation Laboratory and Department of Physics, University of Science and Technology of China, Hefei 230026, China
- Collaborative Innovation Center for Advanced Microstructures, Nanjing 210093, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Tong Zhang
- Department of Physics, State Key Laboratory of Surface Physics and Advanced Material Laboratory, Fudan University, Shanghai 200438, China
- Collaborative Innovation Center for Advanced Microstructures, Nanjing 210093, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| |
Collapse
|
3
|
Malinowski A, Bezusyy VL, Nowicki P. Pseudogap in underdoped cuprate seen in longitudinal magnetoresistance. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:415602. [PMID: 35878602 DOI: 10.1088/1361-648x/ac8405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 07/25/2022] [Indexed: 06/15/2023]
Abstract
We report the results of in-plane magnetotransport study of slightly underdoped cuprate La1.85Sr0.15CuO4(LSCO15) with Ni impurity. Increasing Ni contentycauses a sharp drop in longitudinal magnetoresistance (LMR) in LSCO15 to broaden and move towards higher temperatures. TemperatureTmLMR(y)of this local maximum in LMR coincides with temperatureTdev(y), below which ideal resistivity from the parallel-resistor model deviates from itsT2-dependence. A direct comparison with the hole doping evolution of pseudogap (PG) in La2-xSrxCuO4(LSCO), possible through the mobile-carrier concentration extracted from the thermopower measurements, allows to equate both characteristic temperaturesTmLMR≅Tdevwith PG opening temperatureT∗. The rate of PG closing by magnetic field parallel to the CuO2plane, in measurements up to 9 T, is consistent with spin-paramagnetic effect in this configuration and yields PG closing fieldBpcclose to the second critical fieldBc2predicted for superconducting gap with the help of Werthamer-Helfand-Hohenberg theory. The field anisotropy ofBpcsuggests that orbital degrees of freedom also play a role in PG formation.
Collapse
Affiliation(s)
- Artur Malinowski
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | - Valeriy L Bezusyy
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | - Piotr Nowicki
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| |
Collapse
|
4
|
Liu M, Leveillee J, Lu S, Yu J, Kim H, Tian C, Shi Y, Lai K, Zhang C, Giustino F, Shih CK. Monolayer 1T-NbSe 2 as a 2D-correlated magnetic insulator. SCIENCE ADVANCES 2021; 7:eabi6339. [PMID: 34797708 PMCID: PMC8604411 DOI: 10.1126/sciadv.abi6339] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 09/30/2021] [Indexed: 06/13/2023]
Abstract
Monolayer group V transition metal dichalcogenides in their 1T phase have recently emerged as a platform to investigate rich phases of matter, such as spin liquid and ferromagnetism, resulting from strong electron correlations. Newly emerging 1T-NbSe2 has inspired theoretical investigations predicting collective phenomena such as charge transfer gap and ferromagnetism in two dimensions; however, the experimental evidence is still lacking. Here, by controlling the molecular beam epitaxy growth parameters, we demonstrate the successful growth of high-quality single-phase 1T-NbSe2. By combining scanning tunneling microscopy/spectroscopy and ab initio calculations, we show that this system is a charge transfer insulator with the upper Hubbard band located above the valence band maximum. To demonstrate the electron correlation resulted magnetic property, we create a vertical 1T/2H NbSe2 heterostructure, and we find unambiguous evidence of exchange interactions between the localized magnetic moments in 1T phase and the metallic/superconducting phase exemplified by Kondo resonances and Yu-Shiba-Rusinov–like bound states.
Collapse
Affiliation(s)
- Mengke Liu
- Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA
| | - Joshua Leveillee
- Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA
- Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Shuangzan Lu
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430027, China
| | - Jia Yu
- Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA
| | - Hyunsue Kim
- Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA
| | - Cheng Tian
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Youguo Shi
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Keji Lai
- Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA
| | - Chendong Zhang
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430027, China
| | - Feliciano Giustino
- Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA
- Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Chih-Kang Shih
- Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA
| |
Collapse
|
5
|
Lu S, Nam H, Xiao P, Liu M, Guo Y, Bai Y, Cheng Z, Deng J, Li Y, Zhou H, Henkelman G, Fiete GA, Gao HJ, MacDonald AH, Zhang C, Shih CK. PTCDA Molecular Monolayer on Pb Thin Films: An Unusual π-Electron Kondo System and Its Interplay with a Quantum-Confined Superconductor. PHYSICAL REVIEW LETTERS 2021; 127:186805. [PMID: 34767397 DOI: 10.1103/physrevlett.127.186805] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 09/28/2021] [Indexed: 06/13/2023]
Abstract
The hybridization of magnetism and superconductivity has been an intriguing playground for correlated electron systems, hosting various novel physical phenomena. Usually, localized d or f electrons are central to magnetism. In this study, by placing a PTCDA (3,4,9,10-perylene tetracarboxylic dianhydride) molecular monolayer on ultrathin Pb films, we built a hybrid magnetism/superconductivity (M/SC) system consisting of only sp electronic levels. The magnetic moments reside in the unpaired molecular orbital originating from interfacial charge transfers. We reported distinctive tunneling spectroscopic features of such a Kondo screened π electron impurity lattice on a superconductor in the regime of T_{K}≫Δ, suggesting the formation of a two-dimensional bound states band. Moreover, moiré superlattices with tunable twist angle and the quantum confinement in the ultrathin Pb films provide easy and flexible implementations to tune the interplay between the Kondo physics and the superconductivity, which are rarely present in M/SC hybrid systems.
Collapse
Affiliation(s)
- Shuangzan Lu
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Hyoungdo Nam
- Department of Physics, the University of Texas at Austin, Austin, Texas 78712, USA
| | - Penghao Xiao
- Department of Chemistry, the University of Texas at Austin, Austin, Texas 78712, USA
- Department of Physics & Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H4J5, Canada
| | - Mengke Liu
- Department of Physics, the University of Texas at Austin, Austin, Texas 78712, USA
| | - Yanping Guo
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Yusong Bai
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Zhengbo Cheng
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Jinghao Deng
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Yanxing Li
- Department of Physics, the University of Texas at Austin, Austin, Texas 78712, USA
| | - Haitao Zhou
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Graeme Henkelman
- Department of Chemistry, the University of Texas at Austin, Austin, Texas 78712, USA
| | - Gregory A Fiete
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Hong-Jun Gao
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Allan H MacDonald
- Department of Physics, the University of Texas at Austin, Austin, Texas 78712, USA
| | - Chendong Zhang
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Chih-Kang Shih
- Department of Physics, the University of Texas at Austin, Austin, Texas 78712, USA
| |
Collapse
|
6
|
Chatzopoulos D, Cho D, Bastiaans KM, Steffensen GO, Bouwmeester D, Akbari A, Gu G, Paaske J, Andersen BM, Allan MP. Spatially dispersing Yu-Shiba-Rusinov states in the unconventional superconductor FeTe 0.55Se 0.45. Nat Commun 2021; 12:298. [PMID: 33436594 PMCID: PMC7804303 DOI: 10.1038/s41467-020-20529-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 12/07/2020] [Indexed: 01/29/2023] Open
Abstract
By using scanning tunneling microscopy (STM) we find and characterize dispersive, energy-symmetric in-gap states in the iron-based superconductor FeTe0.55Se0.45, a material that exhibits signatures of topological superconductivity, and Majorana bound states at vortex cores or at impurity locations. We use a superconducting STM tip for enhanced energy resolution, which enables us to show that impurity states can be tuned through the Fermi level with varying tip-sample distance. We find that the impurity state is of the Yu-Shiba-Rusinov (YSR) type, and argue that the energy shift is caused by the low superfluid density in FeTe0.55Se0.45, which allows the electric field of the tip to slightly penetrate the sample. We model the newly introduced tip-gating scenario within the single-impurity Anderson model and find good agreement to the experimental data.
Collapse
Affiliation(s)
- Damianos Chatzopoulos
- grid.5132.50000 0001 2312 1970Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, Leiden, CA 2333 The Netherlands
| | - Doohee Cho
- grid.5132.50000 0001 2312 1970Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, Leiden, CA 2333 The Netherlands ,grid.15444.300000 0004 0470 5454Department of Physics, Yonsei University, Seoul, 03722 Republic of Korea
| | - Koen M. Bastiaans
- grid.5132.50000 0001 2312 1970Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, Leiden, CA 2333 The Netherlands
| | - Gorm O. Steffensen
- grid.5254.60000 0001 0674 042XCenter for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, Copenhagen Ø, 2100 Denmark
| | - Damian Bouwmeester
- grid.5132.50000 0001 2312 1970Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, Leiden, CA 2333 The Netherlands ,grid.5292.c0000 0001 2097 4740Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, Delft, CJ 2628 Netherlands
| | - Alireza Akbari
- grid.419507.e0000 0004 0491 351XMax Planck Institute for the Chemical Physics of Solids, Dresden, D-01187 Germany ,grid.49100.3c0000 0001 0742 4007Max Planck POSTECH Center for Complex Phase Materials, and Department of Physics, POSTECH, Pohang, Gyeongbuk 790-784 Korea
| | - Genda Gu
- grid.202665.50000 0001 2188 4229Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973 USA
| | - Jens Paaske
- grid.5254.60000 0001 0674 042XCenter for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, Copenhagen Ø, 2100 Denmark
| | - Brian M. Andersen
- grid.5254.60000 0001 0674 042XCenter for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, Copenhagen Ø, 2100 Denmark
| | - Milan P. Allan
- grid.5132.50000 0001 2312 1970Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, Leiden, CA 2333 The Netherlands
| |
Collapse
|
7
|
Chen C, Liu C, Liu Y, Wang J. Bosonic Mode and Impurity-Scattering in Monolayer Fe(Te,Se) High-Temperature Superconductors. NANO LETTERS 2020; 20:2056-2061. [PMID: 32045257 DOI: 10.1021/acs.nanolett.0c00028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The electron pairing mechanism has always been one of the most challenging problems in high-temperature superconductors. Fe(Te,Se), as the superconductor with intrinsic topological property, may host Majorana bound states and has attracted tremendous interest. While in bulk Fe(Te,Se) the pairing mechanism has been experimentally investigated, it remains little understood in its two-dimensional limit counterpart. Here, by in situ scanning tunneling spectroscopy, we show clear evidence of the bosonic mode Ω beyond the superconducting gap Δ in monolayer FeTe0.5Se0.5/SrTiO3(001) high-temperature superconductor. Statistically, Ω shows an obvious anticorrelation with Δ and appears below 2Δ, consistent with the spin-excitation nature. Furthermore, the in-gap bound states induced by two types of magnetically different impurities support the sign-reversing pairing scenario. Our results not only suggest that the spin-excitation-like bosonic mode within a sign-reversing pairing plays an essential role in monolayer FeTe0.5Se0.5/SrTiO3(001) but also offer the crucial information for investigating the high-temperature superconductivity in interfacial iron selenides.
Collapse
Affiliation(s)
- Cheng Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
| | - Chaofei Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
| | - Yi Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, P.R. China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, P.R. China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P.R. China
| |
Collapse
|
8
|
Zimmerman AM, Nguyen MD, Scott JW, Halperin WP. Effect of Magnetic Impurities on Superfluid ^{3}He. PHYSICAL REVIEW LETTERS 2020; 124:025302. [PMID: 32004035 DOI: 10.1103/physrevlett.124.025302] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Indexed: 06/10/2023]
Abstract
It is known that both magnetic and nonmagnetic impurities suppress unconventional superconductivity. Here we compare their effect on the paradigm unconventional superconductor, superfluid ^{3}He, using highly dilute silica aerogel. Switching magnetic to nonmagnetic scattering in the same physical system is achieved by coating the aerogel surface with ^{4}He. We find a marginal influence on the transition temperature itself. However, we have discovered that the A phase, which breaks time reversal symmetry, is strongly influenced, while the isotropic B phase is unchanged. Importantly, this occurs only if the impurities are anisotropically distributed on a global scale.
Collapse
Affiliation(s)
- A M Zimmerman
- Northwestern University, Evanston, Illinois 60208, USA
| | - M D Nguyen
- Northwestern University, Evanston, Illinois 60208, USA
| | - J W Scott
- Northwestern University, Evanston, Illinois 60208, USA
| | - W P Halperin
- Northwestern University, Evanston, Illinois 60208, USA
| |
Collapse
|
9
|
Chen L, Zhang YL, Han RS. Visualizing pairing symmetry in nematic superconductors using spin-polarized spectroscopy of magnetic impurities. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:505603. [PMID: 31487693 DOI: 10.1088/1361-648x/ab41c7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We study the spin-polarized spectral properties of Yu-Shiba-Rusinov resonance states induced by magnetic impurities in 2- and 3-dimensional nematic superconductors: few layer Bi2Te3 grown on FeTe0.55Se0.45 (2D) and Cu x Bi2Se3 (3D). We focus on the relationship between pairing symmetry and the spatial structure of spin-polarized spectroscopy. We calculate the spin-polarized local density of states (SP LDOS) and the corresponding Fourier transformation using the T-matrix method for both the 2- and 3-dimensional materials. Various situations with different impurity orientations and different SP LDOSs have been investigated. We find that, like the quasiparticle interference spectrum, the spin-polarized spectroscopy can be applied to distinguish threefold rotation symmetric pairings, e.g. the plain s-wave pairing, chiral p -wave pairing, etc, and nematic pairings in these materials.
Collapse
|
10
|
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.
Collapse
Affiliation(s)
- Chaofei Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | | | | |
Collapse
|
11
|
Graham M, Morr DK. Josephson Scanning Tunneling Spectroscopy in d_{x^{2}-y^{2}}-Wave Superconductors: A Probe for the Nature of the Pseudogap in the Cuprate Superconductors. PHYSICAL REVIEW LETTERS 2019; 123:017001. [PMID: 31386405 DOI: 10.1103/physrevlett.123.017001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 12/02/2018] [Indexed: 06/10/2023]
Abstract
Recent advances in the development of Josephson scanning tunneling spectroscopy (JSTS) have opened a new path for the exploration of unconventional superconductors. We demonstrate that the critical current I_{c}, measured via JSTS, images the spatial form of the superconducting order parameter in d_{x^{2}-y^{2}}-wave superconductors around defects and in the Fulde-Ferrell-Larkin-Ovchinnikov state. Moreover, we show that I_{c} probes the existence of phase-incoherent superconducting correlations in the pseudogap region of the cuprate superconductors, thus providing unprecedented insight into its elusive nature. These results provide the missing theoretical link between the experimentally measured I_{c} and the spatial structure of the superconducting order parameter.
Collapse
Affiliation(s)
- Martin Graham
- University of Illinois at Chicago, Chicago, Illinois 60607, USA
| | - Dirk K Morr
- University of Illinois at Chicago, Chicago, Illinois 60607, USA
| |
Collapse
|
12
|
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.
Collapse
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
| |
Collapse
|
13
|
Chen L, Li HZ, Han RS. Magnetic impurity resonance states for different pairing symmetries in twisted bilayer graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:065601. [PMID: 30523832 DOI: 10.1088/1361-648x/aaf626] [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
In this work, we study the magnetic impurity resonance states in the superconducting phase of 'magic' angle twisted bilayer graphene for different pairing symmetries. Using a two-orbital model on the emergent honeycomb lattice, we find that the resonance states are dramatically different for [Formula: see text]-wave pairing and topological nontrivial pairings. When the magnetic impurity is located at one site of the emergent honeycomb lattice, i.e. the center of the AB spot of the moiré pattern, the spacial distributions of the resonance states will break both the threefold and twofold rotation symmetries of [Formula: see text] point group for pairing symmetries which belong to the irreducible representations of this point group. When the magnetic impurity is located at the center of the emergent honeycomb lattice i.e. the center of the AA spot of the moiré pattern, the appearance of resonance peak at the position close to the impurity can be considered as a strong evidence of non-[Formula: see text]-wave pairing.
Collapse
Affiliation(s)
- Liang Chen
- Mathematics and Physics Department, North China Electric Power University, Beijing 102206, People's Republic of China
| | | | | |
Collapse
|
14
|
Battisti I, Verdoes G, van Oosten K, Bastiaans KM, Allan MP. Definition of design guidelines, construction, and performance of an ultra-stable scanning tunneling microscope for spectroscopic imaging. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:123705. [PMID: 30599565 DOI: 10.1063/1.5064442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 11/19/2018] [Indexed: 06/09/2023]
Abstract
Spectroscopic-imaging scanning tunneling microscopy is a powerful technique to study quantum materials, with the ability to provide information about the local electronic structure with subatomic resolution. However, as most spectroscopic measurements are conducted without feedback to the tip, it is extremely sensitive to vibrations coming from the environment. This requires the use of laboratories with low-vibration facilities combined with a very rigid microscope construction. In this article, we report on the design and fabrication of an ultra-stable scanning tunneling microscope (STM) for spectroscopic-imaging measurements that operates in ultra-high vacuum and at low temperatures (4 K). We start from existing designs with sapphire as the main material and improve the stiffness further by performing finite element analysis calculations for the main components of the microscope to guide design choices on the geometry of the parts. With this strategy, we construct a STM head with measured lowest resonant frequencies above f 0 = 13 kHz for the coarse approach mechanism, a value three times higher than what has been previously reported and in good agreement with the calculations. This allows us to achieve an average vibration level of ∼6 fm / H z , without a dedicated low-vibration lab. We demonstrate the microscope's performance with topographic and spectroscopic measurements on the correlated metal Sr2RhO4, showing the quasiparticle interference pattern in real and reciprocal space with high signal-to-noise ratio.
Collapse
Affiliation(s)
- Irene Battisti
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, The Netherlands
| | - Gijsbert Verdoes
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, The Netherlands
| | - Kees van Oosten
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, The Netherlands
| | - Koen M Bastiaans
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, The Netherlands
| | - Milan P Allan
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, The Netherlands
| |
Collapse
|
15
|
Chen L, Zhao WW, Han RS. Resonance states near a quantum magnetic impurity in single-layer FeSe superconductors with d-wave symmetry. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:305603. [PMID: 29911989 DOI: 10.1088/1361-648x/aacd37] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In this work, we investigate the local density of states (LDOS) near a magnetic impurity in single-layer FeSe superconductors. The two-orbital model with spin-orbit coupling proposed in Agterberg et al (2017 Phys. Rev. Lett. 119 267001) is used to describe the FeSe superconductor. In the strong coupling regime, two impurity resonance peaks appear with opposite resonance energies in the LDOS spectral function. For strong spin-orbit coupling, the superconducting gap in this model is d-wave symmetric with nodes, the spatial distributions of the LDOS at the two resonance energies are fourfold symmetric, which reveals typical characteristic of d-wave pairing. When the spin-orbit coupling is not strong enough to close the superconducting gap, we find that the spatial distribution of the LDOS at one of the resonance energies manifests s-wave symmetry, while the pairing potential preserves d-wave symmetry. This result is consistent with previous experimental investigations.
Collapse
Affiliation(s)
- Liang Chen
- Mathematics and Physics Department, North China Electric Power University, Beijing, 102206, People's Republic of China
| | | | | |
Collapse
|
16
|
Choi S, Johnston S, Jang WJ, Koepernik K, Nakatsukasa K, Ok JM, Lee HJ, Choi HW, Lee AT, Akbari A, Semertzidis YK, Bang Y, Kim JS, Lee J. Correlation of Fe-Based Superconductivity and Electron-Phonon Coupling in an FeAs/Oxide Heterostructure. PHYSICAL REVIEW LETTERS 2017; 119:107003. [PMID: 28949163 DOI: 10.1103/physrevlett.119.107003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Indexed: 06/07/2023]
Abstract
Interfacial phonons between iron-based superconductors (FeSCs) and perovskite substrates have received considerable attention due to the possibility of enhancing preexisting superconductivity. Using scanning tunneling spectroscopy, we studied the correlation between superconductivity and e-ph interaction with interfacial phonons in an iron-based superconductor Sr_{2}VO_{3}FeAs (T_{c}≈33 K) made of alternating FeSC and oxide layers. The quasiparticle interference measurement over regions with systematically different average superconducting gaps due to the e-ph coupling locally modulated by O vacancies in the VO_{2} layer, and supporting self-consistent momentum-dependent Eliashberg calculations provide a unique real-space evidence of the forward-scattering interfacial phonon contribution to the total superconducting pairing.
Collapse
Affiliation(s)
- Seokhwan Choi
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Steven Johnston
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Won-Jun Jang
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
- Center for Axion and Precision Physics Research, Institute for Basic Science (IBS), Daejeon 34051, Korea
| | | | - Ken Nakatsukasa
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Jong Mok Ok
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Hyun-Jung Lee
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Hyun Woo Choi
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Alex Taekyung Lee
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | - Alireza Akbari
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
- Asia Pacific Center for Theoretical Physics, Pohang 37673, Korea
| | - Yannis K Semertzidis
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
- Center for Axion and Precision Physics Research, Institute for Basic Science (IBS), Daejeon 34051, Korea
| | - Yunkyu Bang
- Department of Physics, Chonnam National University, Gwangju 61186, Korea
| | - Jun Sung Kim
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Jhinhwan Lee
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| |
Collapse
|
17
|
Mapping the orbital structure of impurity bound states in a superconductor. Nat Commun 2017; 8:15175. [PMID: 28480879 PMCID: PMC5424157 DOI: 10.1038/ncomms15175] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 03/03/2017] [Indexed: 11/08/2022] Open
Abstract
A magnetic atom inside a superconductor locally distorts superconductivity. It scatters Cooper pairs as a potential with broken time-reversal symmetry, leading to localized bound states with subgap excitation energies, named Shiba states. Most conventional approaches regarding Shiba states treat magnetic impurities as point scatterers with isotropic exchange interaction. Here, we show that the number and the shape of Shiba states are correlated to the spin-polarized atomic orbitals of the impurity, hybridized with the superconductor. Using scanning tunnelling spectroscopy, we spatially map the five Shiba excitations found on subsurface chromium atoms in Pb(111), resolving their particle and hole components. While particle components resemble d orbitals of embedded Cr atoms, hole components differ strongly from them. Density functional theory simulations correlate the orbital shapes to the magnetic ground state of the atom, and identify scattering channels and interactions, all valuable tools for designing atomic-scale superconducting devices.
Collapse
|
18
|
Xu Y, Liu S, Qu N, Cui Y, Gao Q, Chen R, Wang J, Gao F, Hao X. Comparative description of magnetic interactions in Sr 2CuTeO 6 and Sr 2CuWO 6. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:105801. [PMID: 28145278 DOI: 10.1088/1361-648x/aa58cb] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In this work, we comparatively explored the electronic structure and the low-dimensional magnetic interactions of double-perovskite compounds Sr2CuTeO6 and Sr2CuWO6 through first-principles calculations. The electronic structure calculations indicate that the Cu2+ (3d 9) site is the only magnetic active one, whereas Te6+ and W6+ remain in nonmagnetic states with d 10 and d 0 electronic configurations, respectively. The magnetic exchange interactions have been evaluated on the basis of the classical Heisenberg model. Both Sr2CuTeO6 and Sr2CuWO6 should be strong frustrated 2D magnetism, in excellent agreement with the experimental observations. Nevertheless, the nearest-neighbor antiferromagnetic interaction J 1 plays a determined role in constructing the Néel antiferromagnetic ordering within the square Cu2+ framework of Sr2CuTeO6. While, the next-nearest-neighbor antiferromagnetic interaction J 2 transcends the nearest-neighbor interaction J 1, establishes the collinear antiferromagnetic ordering in Sr2CuWO6. The discrimination has been explored and analyzed in detail using density of states, charge density as well as spin density analysis.
Collapse
Affiliation(s)
- Yuanhui Xu
- Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao 066004, People's Republic of China
| | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Erdenemunkh U, Koopman B, Fu L, Chatterjee K, Wise WD, Gu GD, Hudson EW, Boyer MC. Suppression of Superfluid Density and the Pseudogap State in the Cuprates by Impurities. PHYSICAL REVIEW LETTERS 2016; 117:257003. [PMID: 28036192 DOI: 10.1103/physrevlett.117.257003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2016] [Indexed: 06/06/2023]
Abstract
We use scanning tunneling microscopy (STM) to study magnetic Fe impurities intentionally doped into the high-temperature superconductor Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}. Our spectroscopic measurements reveal that Fe impurities introduce low-lying resonances in the density of states at Ω_{1}≈4 meV and Ω_{2}≈15 meV, allowing us to determine that, despite having a large magnetic moment, potential scattering of quasiparticles by Fe impurities dominates magnetic scattering. In addition, using high-resolution spatial characterizations of the local density of states near and away from Fe impurities, we detail the spatial extent of impurity-affected regions as well as provide a local view of impurity-induced effects on the superconducting and pseudogap states. Our studies of Fe impurities, when combined with a reinterpretation of earlier STM work in the context of a two-gap scenario, allow us to present a unified view of the atomic-scale effects of elemental impurities on the pseudogap and superconducting states in hole-doped cuprates; this may help resolve a previously assumed dichotomy between the effects of magnetic and nonmagnetic impurities in these materials.
Collapse
Affiliation(s)
- Unurbat Erdenemunkh
- Department of Physics, Clark University, Worcester, Massachusetts 01610, USA
| | - Brian Koopman
- Department of Physics, Clark University, Worcester, Massachusetts 01610, USA
| | - Ling Fu
- Department of Physics, Clark University, Worcester, Massachusetts 01610, USA
| | - Kamalesh Chatterjee
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - W D Wise
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - G D Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - E W Hudson
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Physics, Pennsylvania State University, State College, Pennsylvania 16802, USA
| | - Michael C Boyer
- Department of Physics, Clark University, Worcester, Massachusetts 01610, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| |
Collapse
|
20
|
Peng Y, Pientka F, Vinkler-Aviv Y, Glazman LI, von Oppen F. Robust Majorana Conductance Peaks for a Superconducting Lead. PHYSICAL REVIEW LETTERS 2015; 115:266804. [PMID: 26765015 DOI: 10.1103/physrevlett.115.266804] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Indexed: 06/05/2023]
Abstract
Experimental evidence for Majorana bound states largely relies on measurements of the tunneling conductance. While the conductance into a Majorana state is in principle quantized to 2e^{2}/h, observation of this quantization has been elusive, presumably due to temperature broadening in the normal-metal lead. Here, we propose to use a superconducting lead instead, whose gap strongly suppresses thermal excitations. For a wide range of tunneling strengths and temperatures, a Majorana state is then signaled by symmetric conductance peaks at eV=±Δ of a universal height G=(4-π)2e(2)/h. For a superconducting scanning tunneling microscope tip, Majorana states appear as spatial conductance plateaus while the conductance varies with the local wave function for trivial Andreev bound states. We discuss effects of nonresonant (bulk) Andreev reflections and quasiparticle poisoning.
Collapse
Affiliation(s)
- Yang Peng
- Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Falko Pientka
- Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Yuval Vinkler-Aviv
- Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Leonid I Glazman
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Felix von Oppen
- Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| |
Collapse
|
21
|
Kreisel A, Choubey P, Berlijn T, Ku W, Andersen BM, Hirschfeld PJ. Interpretation of scanning tunneling quasiparticle interference and impurity states in cuprates. PHYSICAL REVIEW LETTERS 2015; 114:217002. [PMID: 26066452 DOI: 10.1103/physrevlett.114.217002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Indexed: 06/04/2023]
Abstract
We apply a recently developed method combining first principles based Wannier functions with solutions to the Bogoliubov-de Gennes equations to the problem of interpreting STM data in cuprate superconductors. We show that the observed images of Zn on the surface of Bi_{2}Sr_{2}CaCu_{2}O_{8} can only be understood by accounting for the tails of the Cu Wannier functions, which include significant weight on apical O sites in neighboring unit cells. This calculation thus puts earlier crude "filter" theories on a microscopic foundation and solves a long-standing puzzle. We then study quasiparticle interference phenomena induced by out-of-plane weak potential scatterers, and show how patterns long observed in cuprates can be understood in terms of the interference of Wannier functions above the surface. Our results show excellent agreement with experiment and enable a better understanding of novel phenomena in the cuprates via STM imaging.
Collapse
Affiliation(s)
- A Kreisel
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
- Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Peayush Choubey
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
| | - T Berlijn
- Center for Nanophase Materials Sciences and Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - W Ku
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - B M Andersen
- Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - P J Hirschfeld
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
| |
Collapse
|
22
|
Vasala S, Avdeev M, Danilkin S, Chmaissem O, Karppinen M. Magnetic structure of Sr2CuWO6. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:496001. [PMID: 25390820 DOI: 10.1088/0953-8984/26/49/496001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Magnetic structure of the double perovskite Sr2CuWO6 was determined from neutron powder diffraction data. At 3 K the material is magnetically long-range ordered into a collinear antiferromagnetic structure described by a propagation vector k = (0, 1/2, 1/2) with the Cu(II) moments of 0.57(1) μB parallel to the a-axis. The result is in agreement with our previous prediction (Vasala et al 2014 Phys. Rev. B 89 134419) based on electronic structure calculations, showing that the three-dimensional magnetic long-range order is caused by relatively strong antiferromagnetic next-nearest-neighbor interactions.
Collapse
Affiliation(s)
- S Vasala
- Department of Chemistry, Aalto University, PO Box 16100, FI-00076 AALTO, Finland
| | | | | | | | | |
Collapse
|
23
|
Guo Y, Gu S, Feng X, Wang J, Li H, Han T, Dong Y, Jiang X, James TD, Wang B. 3D cross-correlative matrix temperature detection and non-invasive thermal mapping based on a molecular probe. Chem Sci 2014. [DOI: 10.1039/c4sc01611d] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
|
24
|
Alldredge JW, Calleja EM, Dai J, Eisaki H, Uchida S, McElroy K. The k-space origins of scattering in Bi2Sr2CaCu2O8+x. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:335601. [PMID: 23883664 DOI: 10.1088/0953-8984/25/33/335601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We demonstrate a general, computer automated procedure that inverts the reciprocal space scattering data (q-space) that are measured by spectroscopic imaging scanning tunnelling microscopy (SI-STM) in order to determine the momentum space (k-space) scattering structure. This allows a detailed examination of the k-space origins of the quasiparticle interference (QPI) pattern in Bi2Sr2CaCu2O8+x within the theoretical constraints of the joint density of states (JDOS). Our new method allows measurement of the differences between the positive and negative energy dispersions, the gap structure and an energy dependent scattering length scale. Furthermore, it resolves the transition between the dispersive QPI and the checkerboard ([Formula: see text] excitation). We have measured the k-space scattering structure over a wide range of doping (p ∼ 0.22-0.08), including regions where the octet model is not applicable. Our technique allows the complete mapping of the k-space scattering origins of the spatial excitations in Bi2Sr2CaCu2O8+x, which allows for better comparisons between SI-STM and other experimental probes of the band structure. By applying our new technique to such a heavily studied compound, we can validate our new general approach for determining the k-space scattering origins from SI-STM data.
Collapse
|
25
|
Visualizing the atomic-scale electronic structure of the Ca2CuO2Cl2 Mott insulator. Nat Commun 2013; 4:1365. [PMID: 23340405 DOI: 10.1038/ncomms2369] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 12/07/2012] [Indexed: 11/08/2022] Open
Abstract
Although the mechanism of superconductivity in the cuprates remains elusive, it is generally agreed that at the heart of the problem is the physics of doped Mott insulators. A crucial step for solving the high temperature superconductivity puzzle is to elucidate the electronic structure of the parent compound and the behaviour of doped charge carriers. Here we use scanning tunnelling microscopy to investigate the atomic-scale electronic structure of the Ca(2)CuO(2)Cl(2) parent Mott insulator of the cuprates. The full electronic spectrum across the Mott-Hubbard gap is uncovered for the first time, which reveals the particle-hole symmetric and spatially uniform Hubbard bands. Defect-induced charge carriers are found to create broad in-gap electronic states that are strongly localized in space. We show that the electronic structure of pristine Mott insulator is consistent with the Zhang-Rice singlet model, but the peculiar features of the doped electronic states require further investigations.
Collapse
|
26
|
Hu H, Jiang L, Pu H, Chen Y, Liu XJ. Universal impurity-induced bound state in topological superfluids. PHYSICAL REVIEW LETTERS 2013; 110:020401. [PMID: 23383876 DOI: 10.1103/physrevlett.110.020401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Indexed: 06/01/2023]
Abstract
We predict a universal midgap bound state in topological superfluids, induced by either nonmagnetic or magnetic impurities in the strong scattering limit. This universal state is similar to the lowest-energy Caroli-de Gennes-Martricon bound state in a vortex core, but is bound to localized impurities. We argue that the observation of such a universal bound state can be a clear signature for identifying topological superfluids. We theoretically examine our argument for a spin-orbit coupled ultracold atomic Fermi gas trapped in a two-dimensional harmonic potential by performing extensive self-consistent calculations within the mean-field Bogoliubov-de Gennes theory. A realistic scenario for observing a universal bound state in ultracold 40K atoms is proposed.
Collapse
Affiliation(s)
- Hui Hu
- Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122, Australia
| | | | | | | | | |
Collapse
|
27
|
Zeljkovic I, Hoffman JE. Interplay of chemical disorder and electronic inhomogeneity in unconventional superconductors. Phys Chem Chem Phys 2013; 15:13462-78. [DOI: 10.1039/c3cp51387d] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
28
|
Zeljkovic I, Xu Z, Wen J, Gu G, Markiewicz RS, Hoffman JE. Imaging the Impact of Single Oxygen Atoms on Superconducting Bi2+ySr2-yCaCu2O8+x. Science 2012; 337:320-3. [PMID: 22822144 DOI: 10.1126/science.1218648] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Ilija Zeljkovic
- Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USA
| | | | | | | | | | | |
Collapse
|
29
|
First direct observation of the Van Hove singularity in the tunnelling spectra of cuprates. Nat Commun 2011; 2:221. [PMID: 21364560 PMCID: PMC3072078 DOI: 10.1038/ncomms1229] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Accepted: 02/03/2011] [Indexed: 11/08/2022] Open
Abstract
In two-dimensional (2D) lattices, the electronic levels are unevenly spaced, and the density of states (DOS) displays a logarithmic divergence known as the Van Hove singularity (VHS). This is the case in particular for the layered cuprate superconductors. The scanning tunnelling microscope (STM) probes the DOS, and is therefore the ideal tool to observe the VHS. No STM study of cuprate superconductors has reported such an observation so far giving rise to a debate about the possibility of observing directly the normal state DOS in the tunnelling spectra. In this study, we show for the first time that the VHS is unambiguously observed in STM measurements performed on the cuprate Bi₂Sr₂CuO(₆+δ) (Bi-2201). Beside closing the debate, our analysis proves the presence of the pseudogap in the overdoped side of the phase diagram of Bi-2201 and discredits the scenario of the pseudogap phase crossing the superconducting dome.
Collapse
|
30
|
Marz M, Goll G, Löhneysen HV. A scanning tunneling microscope for a dilution refrigerator. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:045102. [PMID: 20441363 DOI: 10.1063/1.3328059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We present the main features of a home-built scanning tunneling microscope that has been attached to the mixing chamber of a dilution refrigerator. It allows scanning tunneling microscopy and spectroscopy measurements down to the base temperature of the cryostat, T approximately 30 mK, and in applied magnetic fields up to 13 T. The topography of both highly ordered pyrolytic graphite and the dichalcogenide superconductor NbSe(2) has been imaged with atomic resolution down to T approximately 50 mK as determined from a resistance thermometer adjacent to the sample. As a test for a successful operation in magnetic fields, the flux-line lattice of superconducting NbSe(2) in low magnetic fields has been studied. The lattice constant of the Abrikosov lattice shows the expected field dependence proportional to 1/square root of B and measurements in the scanning tunneling spectroscopy mode clearly show the superconductive density of states with Andreev bound states in the vortex core.
Collapse
Affiliation(s)
- M Marz
- Physikalisches Institut, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany.
| | | | | |
Collapse
|
31
|
Iavarone M, Karapetrov G, Fedor J, Rosenmann D, Nishizaki T, Kobayashi N. The local effect of magnetic impurities on superconductivity in CoxNbSe2 and MnxNbSe2 single crystals. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:015501. [PMID: 21386227 DOI: 10.1088/0953-8984/22/1/015501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We investigate the effect of individual atomic impurities on the superconducting state that they are embedded in. Using low temperature scanning tunneling microscopy and spectroscopy we could identify Co and Mn atoms in the Co(x)NbSe(2) and Mn(x)NbSe(2) single crystals and observe the influence on the local electronic density of states (LDOS) at 0.4 K. We find that Co is in the weak scattering limit. In this case the LDOS is quite homogeneous on the sample surface, despite the number of defects, and retains sharp coherent superconducting peaks. This is in strong contrast to the effects of Mn impurities, which locally destroy superconductivity. In this case the LDOS shows a strong enhancement of spectral weight inside the superconducting gap even far from the Mn atoms. Moreover, two impurity bound states are found within the superconducting gap at E/Δ(0) = 0.18 and 0.36 at locations close to defects.
Collapse
Affiliation(s)
- M Iavarone
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
| | | | | | | | | | | |
Collapse
|
32
|
Yin Y, Zech M, Williams TL, Wang XF, Wu G, Chen XH, Hoffman JE. Scanning tunneling spectroscopy and vortex imaging in the iron pnictide superconductor BaFe1.8Co0.2As2. PHYSICAL REVIEW LETTERS 2009; 102:097002. [PMID: 19392555 DOI: 10.1103/physrevlett.102.097002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Indexed: 05/27/2023]
Abstract
We present an atomic resolution scanning tunneling spectroscopy study of superconducting BaFe1.8Co0.2As2 single crystals in magnetic fields up to 9 T. At zero field, a single gap with coherence peaks at Delta=6.25 meV is observed in the density of states. At 9 and 6 T, we image a disordered vortex lattice, consistent with isotropic, single flux quantum vortices. Vortex locations are uncorrelated with strong-scattering surface impurities, demonstrating bulk pinning. The vortex-induced subgap density of states fits an exponential decay from the vortex center, from which we extract a coherence length xi=27.6+/-2.9 A, corresponding to an upper critical field Hc2=43 T.
Collapse
Affiliation(s)
- Yi Yin
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | | | | | | | | | | | | |
Collapse
|
33
|
Nieminen J, Lin H, Markiewicz RS, Bansil A. Origin of the electron-hole asymmetry in the scanning tunneling spectrum of the high-temperature Bi2Sr2CaCu2O8+delta superconductor. PHYSICAL REVIEW LETTERS 2009; 102:037001. [PMID: 19257381 DOI: 10.1103/physrevlett.102.037001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2008] [Indexed: 05/27/2023]
Abstract
We have developed a material specific theoretical framework for modeling scanning tunneling spectroscopy (STS) of high-temperature superconducting materials in the normal as well as the superconducting state. Results for Bi2Sr2CaCu2O8+delta (Bi2212) show clearly that the tunneling process strongly modifies the STS spectrum from the local density of states of the dx2-y2 orbital of Cu. The dominant tunneling channel to the surface Bi involves the dx2-y2 orbitals of the four neighboring Cu atoms. In accord with experimental observations, the computed spectrum displays a remarkable asymmetry between the processes of electron injection and extraction, which arises from contributions of Cu dz2 and other orbitals to the tunneling current.
Collapse
Affiliation(s)
- Jouko Nieminen
- Institute of Physics, Tampere University of Technology, P.O. Box 692, 33101 Tampere, Finland.
| | | | | | | |
Collapse
|
34
|
Hiraka H, Matsumura D, Nishihata Y, Mizuki J, Yamada K. Dual nature of a Ni dopant in the hole-type La2-xSrxCuO4 cuprate superconductor. PHYSICAL REVIEW LETTERS 2009; 102:037002. [PMID: 19257382 DOI: 10.1103/physrevlett.102.037002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2008] [Indexed: 05/27/2023]
Abstract
Local distortions around a Ni dopant in the hole-type La2-xSrxCuO4 superconductor system were studied by x-ray-absorption fine structure (XAFS) using single crystals over a wide hole-doping range. Two distinct interatomic distances between Ni and in-plane oxygen appear in the Ni K-edge extended XAFS. Combined with previous results on hole-localization effects by Ni doping, two types of charge states are strongly indicated for Ni. This duality disqualifies a magnetic-impurity picture for Ni dopant in the superconducting phase of cuprates.
Collapse
Affiliation(s)
- H Hiraka
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | | | | | | | | |
Collapse
|
35
|
Albers BJ, Liebmann M, Schwendemann TC, Baykara MZ, Heyde M, Salmeron M, Altman EI, Schwarz UD. Combined low-temperature scanning tunneling/atomic force microscope for atomic resolution imaging and site-specific force spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2008; 79:033704. [PMID: 18377012 DOI: 10.1063/1.2842631] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We present the design and first results of a low-temperature, ultrahigh vacuum scanning probe microscope enabling atomic resolution imaging in both scanning tunneling microscopy (STM) and noncontact atomic force microscopy (NC-AFM) modes. A tuning-fork-based sensor provides flexibility in selecting probe tip materials, which can be either metallic or nonmetallic. When choosing a conducting tip and sample, simultaneous STM/NC-AFM data acquisition is possible. Noticeable characteristics that distinguish this setup from similar systems providing simultaneous STM/NC-AFM capabilities are its combination of relative compactness (on-top bath cryostat needs no pit), in situ exchange of tip and sample at low temperatures, short turnaround times, modest helium consumption, and unrestricted access from dedicated flanges. The latter permits not only the optical surveillance of the tip during approach but also the direct deposition of molecules or atoms on either tip or sample while they remain cold. Atomic corrugations as low as 1 pm could successfully be resolved. In addition, lateral drifts rates of below 15 pm/h allow long-term data acquisition series and the recording of site-specific spectroscopy maps. Results obtained on Cu(111) and graphite illustrate the microscope's performance.
Collapse
Affiliation(s)
- Boris J Albers
- Department of Mechanical Engineering and Center for Research on Interface Structures and Phenomena, Yale University, P.O. Box 208284, New Haven, Connecticut 06520-8284, USA
| | | | | | | | | | | | | | | |
Collapse
|
36
|
Höglund KH, Sandvik AW, Sachdev S. Impurity induced spin texture in quantum critical 2D antiferromagnets. PHYSICAL REVIEW LETTERS 2007; 98:087203. [PMID: 17359124 DOI: 10.1103/physrevlett.98.087203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2006] [Indexed: 05/14/2023]
Abstract
We describe the uniform and staggered magnetization distributions around a vacancy in a quantum critical two-dimensional S=1/2 antiferromagnet. The distributions are delocalized across the entire sample with a universal functional form arising from an uncompensated Berry phase. The numerical results, obtained using quantum Monte Carlo simulations of the Heisenberg model on bilayer lattices with up to approximately equal to 10(5) spins, are in good agreement with the proposed scaling structure. We determine the exponent eta' = 0.40+/-0.02, which governs both the staggered and uniform magnetic structure away from the impurity and also controls the impurity spin dynamics.
Collapse
Affiliation(s)
- Kaj H Höglund
- Department of Physics, Abo Akademi University, Porthansgatan 3, FI-20500 Turku, Finland
| | | | | |
Collapse
|
37
|
Ouazi S, Bobroff J, Alloul H, Le Tacon M, Blanchard N, Collin G, Julien MH, Horvatić M, Berthier C. Impurity-induced local magnetism and density of states in the superconducting state of YBa2Cu3O7. PHYSICAL REVIEW LETTERS 2006; 96:127005. [PMID: 16605949 DOI: 10.1103/physrevlett.96.127005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2005] [Indexed: 05/08/2023]
Abstract
17O NMR is used to probe the local influence of nonmagnetic Zn and magnetic Ni impurities in the superconducting state of optimally doped high TC YBa2Cu3O7. Zn and Ni induce a staggered paramagnetic polarization, similar to that evidenced above TC, with a typical extension xi=3 cell units for Zn and xi>or=3 for Ni. In addition, Zn is observed to induce a local density of states near the Fermi energy in its neighborhood, which also decays over about 3 cell units. Its magnitude decreases sharply with increasing temperature. This allows direct comparison with the STM observations done in BiSCCO.
Collapse
Affiliation(s)
- S Ouazi
- Laboratoire de Physique des Solides, UMR8502, Université Paris XI, 91405 Orsay, France
| | | | | | | | | | | | | | | | | |
Collapse
|
38
|
Andersen BM, Melikyan A, Nunner TS, Hirschfeld PJ. Andreev states near short-ranged pairing potential impurities. PHYSICAL REVIEW LETTERS 2006; 96:097004. [PMID: 16606300 DOI: 10.1103/physrevlett.96.097004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2005] [Indexed: 05/08/2023]
Abstract
We study Andreev states near atomic scale modulations in the pairing potential in both s- and d-wave superconductors with short coherence lengths. For a moderate reduction of the local gap, the states exist only close to the gap edge. If one allows for local sign changes of the order parameter, however, resonances can occur at energies close to the Fermi level. The local density of states (LDOS) around such pairing potential defects strongly resembles the patterns observed by tunneling measurements around Zn impurities in Bi2Sr2CaCu2O8+x (BSCCO). We discuss how this phase impurity model of the Zn LDOS pattern can be distinguished from other proposals experimentally.
Collapse
Affiliation(s)
- Brian M Andersen
- Department of Physics, University of Florida, Gainesville, Florida 32611-8440, USA
| | | | | | | |
Collapse
|
39
|
Pimenov AV, Boris AV, Yu L, Hinkov V, Wolf T, Tallon JL, Keimer B, Bernhard C. Nickel impurity-induced enhancement of the pseudogap of cuprate high-T(c) superconductors. PHYSICAL REVIEW LETTERS 2005; 94:227003. [PMID: 16090428 DOI: 10.1103/physrevlett.94.227003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2004] [Indexed: 05/03/2023]
Abstract
The influence of magnetic Ni and nonmagnetic Zn impurities on the normal-state pseudogap (PG) in the c-axis optical conductivity of (Sm,Nd)Ba(2){Cu(1-y)(Ni,Zn)(y)}(3)O(7-delta) crystals was studied by spectral ellipsometry. We find that these impurities, which strongly suppress superconductivity, have a profoundly different impact on the PG. Zn gives rise to a gradual and inhomogeneous PG suppression while Ni strongly enhances the PG. Our results challenge theories that relate the PG either to precursor superconductivity or to other phases with exotic order parameters, such as flux phase or d-density wave states, that should be suppressed by potential scattering. The apparent difference between magnetic and nonmagnetic impurities instead points towards an important role of magnetic correlations in the PG state.
Collapse
Affiliation(s)
- A V Pimenov
- Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | | | | | | | | | | | | | | |
Collapse
|
40
|
Davidson BA, Ramazashvili R, Kos S, Eckstein JN. Broken particle-hole symmetry at atomically flat a-axis YBa2Cu3O7-delta interfaces. PHYSICAL REVIEW LETTERS 2004; 93:107004. [PMID: 15447441 DOI: 10.1103/physrevlett.93.107004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2003] [Indexed: 05/24/2023]
Abstract
We have studied quasiparticle tunneling into atomically flat a-axis films of YBa(2)Cu(3)O(7-delta) and DyBa(2)Cu(3)O(7-delta) through epitaxial CaTiO3 barriers. The junction heterostructures were grown by oxide molecular beam epitaxy and were carefully optimized using in situ monitoring techniques, resulting in unprecedented crystalline perfection of the superconductor-insulator interface. Below T(c), the tunneling conductance shows the evolution of a large unexpected asymmetrical feature near zero-bias. This is evidence that superconducting YBCO crystals, atomically truncated along the lobe direction with a titanate layer, have intrinsically broken particle-hole symmetry over macroscopically large areas.
Collapse
Affiliation(s)
- Bruce A Davidson
- Physics Department, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
| | | | | | | |
Collapse
|
41
|
Kenzelmann M, Xu G, Zaliznyak IA, Broholm C, DiTusa JF, Aeppli G, Ito T, Oka K, Takagi H. Structure of end states for a Haldane spin chain. PHYSICAL REVIEW LETTERS 2003; 90:087202. [PMID: 12633455 DOI: 10.1103/physrevlett.90.087202] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2002] [Indexed: 05/24/2023]
Abstract
Inelastic neutron scattering was used to probe edge states in a quantum spin liquid. The experiment was performed on finite length antiferromagnetic spin-1 chains in Y2BaNi1-xMgxO5. At finite fields, there is a Zeeman resonance below the Haldane gap. The wave-vector dependence of its intensity provides direct evidence for staggered magnetization at chain ends, which decays exponentially towards the bulk [xi=8(1) at T=0.1 K]. Continuum contributions to the chain-end spectrum indicate interchain segment interactions. We also observe a finite size blueshift of the Haldane gap.
Collapse
Affiliation(s)
- M Kenzelmann
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
42
|
Moradian R, Györffy BL, Annett JF. Impurity bound states in disordered d-wave superconductors. PHYSICAL REVIEW LETTERS 2002; 89:287002. [PMID: 12513174 DOI: 10.1103/physrevlett.89.287002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2002] [Indexed: 05/24/2023]
Abstract
Recent STM experiments on Bi2Sr2Ca2Cu3O10 observed sharp bound states associated with Zn and Ni impurities, as previously predicted theoretically. Here we extend the theory to the case of a finite concentration of impurities. Using the nonlocal coherent potential approximation, we show that the resonance peak both broadens and shifts as a function of impurity concentration.
Collapse
|
43
|
Chen CT, Seneor P, Yeh NC, Vasquez RP, Bell LD, Jung CU, Kim JY, Park MS, Kim HJ, Lee SI. Strongly correlated s-wave superconductivity in the N-type infinite-layer cuprate. PHYSICAL REVIEW LETTERS 2002; 88:227002. [PMID: 12059447 DOI: 10.1103/physrevlett.88.227002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2001] [Indexed: 05/23/2023]
Abstract
Quasiparticle tunneling spectra of the electron-doped ( n-type) infinite-layer cuprate Sr0.9La0.1CuO2 reveal characteristics that counter a number of common phenomena in the hole-doped ( p-type) cuprates. The optimally doped Sr0.9La0.1CuO2 with T(c) = 43 K exhibits a momentum-independent superconducting gap Delta = 13.0+/-1.0 meV that substantially exceeds the BCS value, and the spectral characteristics indicate insignificant quasiparticle damping by spin fluctuations and the absence of pseudogap. The response to quantum impurities in the Cu sites also differs fundamentally from that of the p-type cuprates with d(x(2)-y(2))-wave pairing symmetry.
Collapse
Affiliation(s)
- C-T Chen
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Martin I, Balatsky AV, Zaanen J. Impurity states and interlayer tunneling in high temperature superconductors. PHYSICAL REVIEW LETTERS 2002; 88:097003. [PMID: 11864045 DOI: 10.1103/physrevlett.88.097003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2000] [Indexed: 05/23/2023]
Abstract
We argue that the scanning tunneling microscope (STM) images of resonant states generated by doping Zn or Ni impurities into Cu-O planes of BSCCO are the result of quantum interference of the impurity signal coming from several distinct paths. The impurity image seen on the surface is greatly affected by interlayer tunneling matrix elements. We find that the optimal tunneling path between the STM tip and the metal (Cu, Zn, or Ni) d(x(2)-y(2)) orbitals in the Cu-O plane involves intermediate excited states. This tunneling path leads to the fourfold nonlocal filter of the impurity state in Cu-O plane that explains the experimental impurity spectra. Applications of the tunneling filter to the Cu vacancy defects and "direct" tunneling into Cu-O planes are also discussed.
Collapse
Affiliation(s)
- I Martin
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | | | | |
Collapse
|
45
|
Derro DJ, Hudson EW, Lang KM, Pan SH, Davis JC, Markert JT, de Lozanne AL. Nanoscale one-dimensional scattering resonances in the CuO chains of YBa(2)Cu(3)O(6+x). PHYSICAL REVIEW LETTERS 2002; 88:097002. [PMID: 11864044 DOI: 10.1103/physrevlett.88.097002] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2001] [Indexed: 05/23/2023]
Abstract
We present scanning tunneling spectroscopy measurements of the CuO chain plane in YBa(2)Cu(3)O(6+x), showing an approximately 25 meV gap in the local density of states (LDOS) filled by numerous intragap resonances: intense peaks in LDOS spectra associated with one-dimensional, Friedel-like oscillations. We discuss how these phenomena shed light on recent results from other probes, as well as their implications for phenomena in the superconducting CuO(2) plane.
Collapse
Affiliation(s)
- D J Derro
- Department of Physics, University of Texas, Austin, TX 78712, USA
| | | | | | | | | | | | | |
Collapse
|
46
|
Dobrowolski T. Kink production in the presence of impurities. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 65:036136. [PMID: 11909194 DOI: 10.1103/physreve.65.036136] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2001] [Indexed: 05/23/2023]
Abstract
The production of kinks during a quench in an overdamped regime of phi(4) model is investigated. Expelling defects from regions of nonzero force coming from the impurity are predicted.
Collapse
Affiliation(s)
- T Dobrowolski
- Institute of Physics AP, Podchorazych 2, 30-084 Cracow, Poland
| |
Collapse
|
47
|
Fabrizio M, Dell'Anna L, Castellani C. Quasiparticle conductivities in disordered d-wave superconductors. PHYSICAL REVIEW LETTERS 2002; 88:076603. [PMID: 11863927 DOI: 10.1103/physrevlett.88.076603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2001] [Indexed: 05/23/2023]
Abstract
We study the quasiparticle transport coefficients in disordered d-wave superconductors. We find that spin and charge excitations are generally localized unless magnetic impurities are present. If the system is close to a nesting point in the impurity-scattering unitary limit, the tendency towards localization is reduced while the quasiparticle density of states gets enhanced by disorder. We also show that the residual repulsive interaction among quasiparticles has a delocalizing effect and increases the density of states.
Collapse
Affiliation(s)
- Michele Fabrizio
- Istituto Nazionale di Fisica della Materia and International School for Advanced Studies (SISSA), Via Beirut 2-4, I-34014 Trieste, Italy
| | | | | |
Collapse
|
48
|
Wang QH. Mechanism of pseudogap probed by a local impurity. PHYSICAL REVIEW LETTERS 2002; 88:057002. [PMID: 11863768 DOI: 10.1103/physrevlett.88.057002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2001] [Indexed: 05/23/2023]
Abstract
The response to a local strong nonmagnetic impurity in the pseudogap phase is examined in two distinctly different scenarios: phase fluctuation (PF) of pairing field and d-density-wave (DDW) order. In the PF scenario, the resonance state is generally double peaked near the Fermi level, and is abruptly broadened by vortex fluctuations slightly above the transition temperature. In the DDW scenario, the resonance is single peaked and remains sharp up to gradual intrinsic thermal broadening, and the resonance energy is analytically determined to be at minus of the chemical potential.
Collapse
Affiliation(s)
- Qiang-Hua Wang
- National Laboratory of Solid State Microstructures, Institute for Solid State Physics, Nanjing University, Nanjing 210093, China
| |
Collapse
|
49
|
Lang KM, Madhavan V, Hoffman JE, Hudson EW, Eisaki H, Uchida S, Davis JC. Imaging the granular structure of high-Tc superconductivity in underdoped Bi2Sr2CaCu2O8+delta. Nature 2002; 415:412-6. [PMID: 11807550 DOI: 10.1038/415412a] [Citation(s) in RCA: 638] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Granular superconductivity occurs when microscopic superconducting grains are separated by non-superconducting regions; Josephson tunnelling between the grains establishes the macroscopic superconducting state. Although crystals of the copper oxide high-transition-temperature (high-Tc) superconductors are not granular in a structural sense, theory suggests that at low levels of hole doping the holes can become concentrated at certain locations resulting in hole-rich superconducting domains. Granular superconductivity arising from tunnelling between such domains would represent a new view of the underdoped copper oxide superconductors. Here we report scanning tunnelling microscope studies of underdoped Bi2Sr2CaCu2O8+delta that reveal an apparent segregation of the electronic structure into superconducting domains that are approximately 3 nm in size (and local energy gap <50 meV), located in an electronically distinct background. We used scattering resonances at Ni impurity atoms as 'markers' for local superconductivity; no Ni resonances were detected in any region where the local energy gap Delta > 50 +/- 2.5 meV. These observations suggest that underdoped Bi2Sr2CaCu2O8+delta is a mixture of two different short-range electronic orders with the long-range characteristics of a granular superconductor.
Collapse
Affiliation(s)
- K M Lang
- Department of Physics, University of California, Berkeley, California 94720, USA
| | | | | | | | | | | | | |
Collapse
|
50
|
|