Time-reversal symmetry-breaking charge order in a kagome superconductor

Journal Article · 08 February 2022 · Nature (London)

DOI: https://doi.org/10.1038/s41586-021-04327-z · OSTI ID:1871902

Mielke, III, Charles  ^[1]; Das, Debarchan  ^[2]; Yin, J. -X. ^[3]; Liu, H. ^[4]; Gupta, R. ^[2]; Jiang, Y. -X. ^[3]; Medarde, M. ^[2]; Wu, X. ^[5]; Lei, Hechang C.  ^[6]; Chang, J. ^[7]; Dai, Pengcheng ^[8]; Si, Qimiao  ^[8]; Miao, H. ^[9]; Thomale, Ronny  ^[10]; Neupert, Titus  ^[7]; Shi, Y. ^[11]; Khasanov, Rustem  ^[2]; Hasan, M. Z.  ^[12]; Luetkens, Hubertus  ^[2]; Guguchia, Z.  ^[2]

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1. Paul Scherrer Inst. (PSI), Villigen (Switzerland); Univ. of Zurich (Switzerland)
2. Paul Scherrer Inst. (PSI), Villigen (Switzerland)
3. Princeton Univ., NJ (United States)
4. Chinese Academy of Sciences (CAS), Beijing (China); University of Chinese Academy of Sciences, Beijing (China)
5. Max Planck Institute of Solid State Research, Stuttgart (Germany)
6. Renmin Univ. of China, Beijing (China)
7. Univ. of Zurich (Switzerland)
8. Rice Univ., Houston, TX (United States)
9. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
10. Univ. of Wurzburg (Germany); Indian Inst. of Technology (IIT), Chennai (India)
11. Chinese Academy of Sciences (CAS), Beijing (China); University of Chinese Academy of Sciences, Beijing (China); Songshan Lake Materials Laboratory, Guangdong (China)
12. Princeton Univ., NJ (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Science Center

The kagome lattice¹, which is the most prominent structural motif in quantum physics, benefits from inherent non-trivial geometry so that it can host diverse quantum phases, ranging from spin-liquid phases, to topological matter, to intertwined orders^{2,3,4,5,6,7,8} and, most rarely, to unconventional superconductivity^6,9. Recently, charge sensitive probes have indicated that the kagome superconductors AV₃Sb₅ (A = K, Rb, Cs)^9,10,11 exhibit unconventional chiral charge order^{12,13,14,15,16,17,18,19,} which is analogous to the long-sought-after quantum order in the Haldane model²⁰ or Varma model²¹. However, direct evidence for the time-reversal symmetry breaking of the charge order remains elusive. Here we use muon spin relaxation to probe the kagome charge order and superconductivity in KV₃Sb₅. We observe a noticeable enhancement of the internal field width sensed by the muon ensemble, which takes place just below the charge ordering temperature and persists into the superconducting state. Notably, the muon spin relaxation rate below the charge ordering temperature is substantially enhanced by applying an external magnetic field. We further show the multigap nature of superconductivity in KV₃Sb₅ and that the T_c/λ$$^{-2}_{ab}$$ ratio (where T_c is the superconducting transition temperature and λ_ab is the magnetic penetration depth in the kagome plane) is comparable to those of unconventional high-temperature superconductors. Our results point to time-reversal symmetry-breaking charge order intertwining with unconventional superconductivity in the correlated kagome lattice.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; Swiss National Science Foundation (SNSF); Gordon and Betty Moore Foundation; Robert A. Welch Foundation; Beijing Natural Science Foundation; National Key Research and Development Program of China; National Natural Science Foundation of China
• Grant/Contract Number: AC05-00OR22725; FG02-05ER46200; SC0018197; SC0012311
• OSTI ID: 1871902
• Journal Information: Nature (London), Journal Name: Nature (London) Journal Issue: 7896 Vol. 602; ISSN 0028-0836
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United States
• Language: English