Emergent superconducting fluctuations in compressed kagome superconductor CsV3Sb5

Xikai Wen; Fanghang Yu; Zhigang Gui; Yuqing Zhang; Xingyuan Hou; Lei Shan; Tao Wu; Ziji Xiang; Zhenyu Wang; Jianjun Ying; Xianhui Chen

doi:10.1016/j.scib.2023.01.020

Emergent superconducting fluctuations in compressed kagome superconductor CsV₃Sb₅

Sci Bull (Beijing). 2023 Feb 15;68(3):259-265. doi: 10.1016/j.scib.2023.01.020. Epub 2023 Jan 18.

Authors

Xikai Wen¹, Fanghang Yu¹, Zhigang Gui¹, Yuqing Zhang¹, Xingyuan Hou², Lei Shan³, Tao Wu¹, Ziji Xiang¹, Zhenyu Wang¹, Jianjun Ying⁴, Xianhui Chen⁵

Affiliations

¹ Department of Physics, and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei 230026, China.
² Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China.
³ Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China; Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education, Anhui University, Hefei 230601, China.
⁴ Department of Physics, and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei 230026, China. Electronic address: yingjj@ustc.edu.cn.
⁵ Department of Physics, and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei 230026, China; CAS Center for Excellence in Quantum Information and Quantum Physics, Hefei 230026, China. Electronic address: chenxh@ustc.edu.cn.

PMID: 36681589
DOI: 10.1016/j.scib.2023.01.020

Abstract

The recent discovery of superconductivity (SC) and charge density wave (CDW) in kagome metals AV₃Sb₅ (A = K, Rb, Cs) provides an ideal playground for the study of emergent electronic orders. Application of moderate pressure leads to a two-dome-shaped SC phase regime in CsV₃Sb₅ accompanied by the destabilizing of CDW phase. Nonetheless, the nature of this pressure-tuned SC state and its interplay with the CDW are yet to be explored. Here, we perform soft point-contact spectroscopy (SPCS) measurements in CsV₃Sb₅ to investigate the evolution of superconducting order parameter with pressure. Surprisingly, we find that the superconducting gap is significantly enhanced between the two SC domes, at which the zero-resistance temperature is suppressed and the transition is remarkably broadened. Moreover, the temperature-dependence of the SC gap in this pressure range severely deviates from the conventional Bardeen-Cooper-Schrieffer (BCS) behavior, evidencing for strong Cooper pair phase fluctuations. These findings reveal the complex intertwining of the CDW with SC in the compressed CsV₃Sb₅, suggesting striking parallel to the cuprate superconductor La_2-_xBa_xCuO₄. Our results point to the essential role of charge degree of freedom in the development of intertwining electronic orders, and thus provide new constraints for theories.

Keywords: Charge density wave; Kagome superconductor; Superconducting fluctuations.