A unique van Hove singularity in kagome superconductor CsV3-xTaxSb5 with enhanced superconductivity

Yang Luo; Yulei Han; Jinjin Liu; Hui Chen; Zihao Huang; Linwei Huai; Hongyu Li; Bingqian Wang; Jianchang Shen; Shuhan Ding; Zeyu Li; Shuting Peng; Zhiyuan Wei; Yu Miao; Xiupeng Sun; Zhipeng Ou; Ziji Xiang; Makoto Hashimoto; Donghui Lu; Yugui Yao; Haitao Yang; Xianhui Chen; Hong-Jun Gao; Zhenhua Qiao; Zhiwei Wang; Junfeng He

doi:10.1038/s41467-023-39500-7

A unique van Hove singularity in kagome superconductor CsV_3-xTa_xSb₅ with enhanced superconductivity

Nat Commun. 2023 Jun 28;14(1):3819. doi: 10.1038/s41467-023-39500-7.

Authors

Yang Luo^#¹, Yulei Han^#², Jinjin Liu^#^{3

4}, Hui Chen^#⁵, Zihao Huang⁵, Linwei Huai¹, Hongyu Li¹, Bingqian Wang¹, Jianchang Shen¹, Shuhan Ding¹, Zeyu Li¹, Shuting Peng¹, Zhiyuan Wei¹, Yu Miao¹, Xiupeng Sun¹, Zhipeng Ou¹, Ziji Xiang¹, Makoto Hashimoto⁶, Donghui Lu⁶, Yugui Yao^{3

4}, Haitao Yang⁵, Xianhui Chen¹, Hong-Jun Gao⁷, Zhenhua Qiao^{8

9}, Zhiwei Wang^{10

11

12}, Junfeng He¹³

Affiliations

¹ Department of Physics and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.
² Department of Physics, Fuzhou University, Fuzhou, Fujian, 350108, China.
³ Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China.
⁴ Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology, Beijing, 100081, China.
⁵ Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
⁶ Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA.
⁷ Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China. [email protected].
⁸ Department of Physics and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China. [email protected].
⁹ International Center for Quantum Design of Functional Materials, University of Science and Technology of China, Hefei, Anhui, 230026, China. [email protected].
¹⁰ Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China. [email protected].
¹¹ Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology, Beijing, 100081, China. [email protected].
¹² Material Science Center, Yangtze Delta Region Academy of Beijing Institute of Technology, Jiaxing, 314011, China. [email protected].
¹³ Department of Physics and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China. [email protected].

^# Contributed equally.

Abstract

Van Hove singularity (VHS) has been considered as a driving source for unconventional superconductivity. A VHS in two-dimensional (2D) materials consists of a saddle point connecting electron-like and hole-like bands. In a rare case, when a VHS appears at Fermi level, both electron-like and hole-like conduction can coexist, giving rise to an enhanced density of states as well as an attractive component of Coulomb interaction for unconventional electronic pairing. However, this van Hove scenario is often destroyed by an incorrect chemical potential or competing instabilities. Here, by using angle-resolved photoemission measurements, we report the observation of a VHS perfectly aligned with the Fermi level in a kagome superconductor CsV_3-xTa_xSb₅ (x ~ 0.4), in which a record-high superconducting transition temperature is achieved among all the current variants of AV₃Sb₅ (A = Cs, Rb, K) at ambient pressure. Doping dependent measurements reveal the important role of van Hove scenario in boosting superconductivity, and spectroscopic-imaging scanning tunneling microscopy measurements indicate a distinct superconducting state in this system.