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Wang S, Yu Y, Hao J, Liang K, Xiang B, Zhu J, Lin Y, Pan Y, Gu G, Watanabe K, Taniguchi T, Qi Y, Zhang Y, Wang Y. Oscillating paramagnetic Meissner effect and Berezinskii-Kosterlitz-Thouless transition in underdoped Bi 2Sr 2CaCu 2O 8+δ. Natl Sci Rev 2024; 11:nwad249. [PMID: 38577674 PMCID: PMC10989300 DOI: 10.1093/nsr/nwad249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 07/01/2023] [Accepted: 08/31/2023] [Indexed: 04/06/2024] Open
Abstract
Superconducting phase transitions in two dimensions lie beyond the description of the Ginzburg-Landau symmetry-breaking paradigm for three-dimensional superconductors. They are Berezinskii-Kosterlitz-Thouless (BKT) transitions of paired-electron condensate driven by the unbinding of topological excitations, i.e. vortices. The recently discovered monolayers of layered high-transition-temperature ([Formula: see text]) cuprate superconductor Bi2Sr2CaCu2O8+δ (Bi2212) meant that this 2D superconductor promised to be ideal for the study of unconventional superconductivity. But inhomogeneity posed challenges for distinguishing BKT physics from charge correlations in this material. Here, we utilize the phase sensitivity of scanning superconducting quantum interference device microscopy susceptometry to image the local magnetic response of underdoped Bi2212 from the monolayer to the bulk throughout its phase transition. The monolayer segregates into domains with independent phases at elevated temperatures below [Formula: see text]. Within a single domain, we find that the susceptibility oscillates with flux between diamagnetism and paramagnetism in a Fraunhofer-like pattern up to [Formula: see text]. The finite modulation period, as well as the broadening of the peaks when approaching [Formula: see text] from below, suggests well-defined vortices that are increasingly screened by the dissociation of vortex-antivortex plasma through a BKT transition. In the multilayers, the susceptibility oscillation differs in a small temperature regime below [Formula: see text], consistent with a dimensional crossover led by interlayer coupling. Serving as strong evidence for BKT transition in the bulk, we observe a sharp jump in phase stiffness and paramagnetism at small fields just below [Formula: see text]. These results unify the superconducting phase transitions from the monolayer to the bulk underdoped Bi2212, and can be collectively referred to as the BKT transition with interlayer coupling.
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Affiliation(s)
- Shiyuan Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yijun Yu
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Jinxiang Hao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Keyi Liang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Bingke Xiang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Jinjiang Zhu
- 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
| | - Yinping Pan
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Genda Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan
| | - Yang Qi
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yuanbo Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, 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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Yamashita A, Shukunami Y, Mizuguchi Y. Improvement of critical current density of REBa 2Cu 3O 7-δ by increase in configurational entropy of mixing. R Soc Open Sci 2022; 9:211874. [PMID: 35360352 PMCID: PMC8965395 DOI: 10.1098/rsos.211874] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 03/01/2022] [Indexed: 05/03/2023]
Abstract
REBa2Cu3O7- δ (RE123, RE: rare earth) is one of the high-temperature superconductors with a transition temperature (T c) exceeding 90 K. Because of its high-T c and large critical current density (J c) under magnetic fields, RE123 superconductors have been expected to play a key role in superconductivity application. To accelerate application researches on RE123-based devices, further improvements of J c characteristics have been desired. In this study, we investigated the effects of high-entropy alloying at the RE site on the superconducting properties, through the measurements of local (intra-grain) J c ( J c local ) by a remanent magnetization method. We found that J c local shows a trend to be improved when four or five RE elements are mixed at the RE site, which results in high configurational entropy of mixing (ΔS mix). All samples exhibited an order of few MA cm-2 which is a criterion for practical application and the highest J c local resulted in a value of around 7.0 MA cm-2 at T = 2.0 K. Because high-entropy alloying can improve J c local of RE123 superconductors, our entropy-engineering strategy introduced here would be useful for the development of RE123 superconducting materials available under high magnetic fields.
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Affiliation(s)
- Aichi Yamashita
- Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan
| | - Yuta Shukunami
- Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan
| | - Yoshikazu Mizuguchi
- Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan
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