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Hu S, Qiao J, Gu G, Xue QK, Zhang D. Vortex entropy and superconducting fluctuations in ultrathin underdoped Bi 2Sr 2CaCu 2O 8+x superconductor. Nat Commun 2024; 15:4818. [PMID: 38844439 PMCID: PMC11156657 DOI: 10.1038/s41467-024-48899-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 05/15/2024] [Indexed: 06/09/2024] Open
Abstract
Vortices in superconductors can help identify emergent phenomena but certain fundamental aspects of vortices, such as their entropy, remain poorly understood. Here, we study the vortex entropy in underdoped Bi2Sr2CaCu2O8+x by measuring both magneto-resistivity and Nernst effect on ultrathin flakes (≤2 unit-cell). We extract the London penetration depth from the magneto-transport measurements on samples with different doping levels. It reveals that the superfluid phase stiffness ρs scales linearly with the superconducting transition temperature Tc, down to the extremely underdoped case. On the same batch of ultrathin flakes, we measure the Nernst effect via on-chip thermometry. Together, we obtain the vortex entropy and find that it decays exponentially with Tc or ρs. We further analyze the Nernst signal above Tc in the framework of Gaussian superconducting fluctuations. The combination of electrical and thermoelectric measurements in the two-dimensional limit provides fresh insight into high temperature superconductivity.
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Affiliation(s)
- Shuxu Hu
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, China
| | - Jiabin Qiao
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, China.
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement, School of Physics, Beijing Institute of Technology, Beijing, China.
- Beijing Academy of Quantum Information Sciences, Beijing, China.
| | - Genda Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA
| | - Qi-Kun Xue
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, China.
- Beijing Academy of Quantum Information Sciences, Beijing, China.
- Southern University of Science and Technology, Shenzhen, China.
- Frontier Science Center for Quantum Information, Beijing, China.
| | - Ding Zhang
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, China.
- Beijing Academy of Quantum Information Sciences, Beijing, China.
- Frontier Science Center for Quantum Information, Beijing, China.
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan.
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Wang H, Zhu Y, Bai Z, Wang Z, Hu S, Xie HY, Hu X, Cui J, Huang M, Chen J, Ding Y, Zhao L, Li X, Zhang Q, Gu L, Zhou XJ, Zhu J, Zhang D, Xue QK. Prominent Josephson tunneling between twisted single copper oxide planes of Bi 2Sr 2-xLa xCuO 6+y. Nat Commun 2023; 14:5201. [PMID: 37626041 PMCID: PMC10457331 DOI: 10.1038/s41467-023-40525-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Accepted: 07/21/2023] [Indexed: 08/27/2023] Open
Abstract
Josephson tunneling in twisted cuprate junctions provides a litmus test for the pairing symmetry, which is fundamental for understanding the microscopic mechanism of high temperature superconductivity. This issue is rekindled by experimental advances in van der Waals stacking and the proposal of an emergent d+id-wave. So far, all experiments have been carried out on Bi2Sr2CaCu2O8+x (Bi-2212) with double CuO2 planes but show controversial results. Here, we investigate junctions made of Bi2Sr2-xLaxCuO6+y (Bi-2201) with single CuO2 planes. Our on-site cold stacking technique ensures uncompromised crystalline quality and stoichiometry at the interface. Junctions with carefully calibrated twist angles around 45° show strong Josephson tunneling and conventional temperature dependence. Furthermore, we observe standard Fraunhofer diffraction patterns and integer Fiske steps in a junction with a twist angle of 45.0±0.2°. Together, these results pose strong constraints on the d or d+id-wave pairing and suggest an indispensable isotropic pairing component.
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Affiliation(s)
- Heng Wang
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Yuying Zhu
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China.
- Hefei National Laboratory, Hefei, 230088, China.
| | - Zhonghua Bai
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Zechao Wang
- National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing, 100084, China
- Ji Hua Laboratory, Foshan, Guangdong, 528200, China
| | - Shuxu Hu
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Hong-Yi Xie
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China
| | - Xiaopeng Hu
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Jian Cui
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China
| | - Miaoling Huang
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China
| | - Jianhao Chen
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100091, China
| | - Ying Ding
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Lin Zhao
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Xinyan Li
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Qinghua Zhang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Lin Gu
- National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing, 100084, China
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - X J Zhou
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Jing Zhu
- National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing, 100084, China
- Ji Hua Laboratory, Foshan, Guangdong, 528200, China
| | - Ding Zhang
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China.
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China.
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan.
| | - Qi-Kun Xue
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China.
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China.
- Southern University of Science and Technology, Shenzhen, 518055, China.
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Ji JY, Bao T, Wang H, Xu Y, Zhang D, Xue QK. Homogeneous Lateral Lithium Intercalation into Transition Metal Dichalcogenides via Ion Backgating. NANO LETTERS 2022; 22:7336-7342. [PMID: 36122383 DOI: 10.1021/acs.nanolett.2c01705] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Lithium intercalation has become a versatile tool for realizing emergent quantum phenomena in two-dimensional (2D) materials. However, the insertion of lithium ions may be accompanied by the creation of wrinkles and cracks, which prevents the material from manifesting its intrinsic properties under substantial charge injection. By using the recently developed ion backgating technique, we successfully realize lateral intercalation in 1T-TiSe2 and 2H-NbSe2, which shows substantially improved sample homogeneity. The homogeneity at high lithium doping is not only demonstrated via low-temperature transport measurements but also directly visualized by topographical imaging through in situ atomic force microscopy (AFM). The application of lateral intercalation to a broad spectrum of 2D materials can greatly facilitate the search for exotic quantum phenomena.
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Affiliation(s)
- Jia-Yi Ji
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
| | - Ting Bao
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
| | - Heng Wang
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
| | - Yong Xu
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
- Frontier Science Center for Quantum Information, Beijing 100084, China
- Collaborative Innovation Center for Quantum Matter, Beijing 100084, China
| | - Ding Zhang
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
- Collaborative Innovation Center for Quantum Matter, Beijing 100084, China
| | - Qi-Kun Xue
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
- Collaborative Innovation Center for Quantum Matter, Beijing 100084, China
- Southern University of Science and Technology, Shenzhen 518055, China
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