1. Bulk evidence of anisotropic $s$-wave pairing with no sign change in the kagome superconductor CsV$_3$Sb$_5$
- Author
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Roppongi, M., Ishihara, K., Tanaka, Y., Ogawa, K., Okada, K., Liu, S., Mukasa, K., Mizukami, Y., Uwatoko, Y., Grasset, R., Konczykowski, M., Ortiz, B. R., Wilson, S. D., Hashimoto, K., and Shibauchi, T.
- Subjects
Condensed Matter - Superconductivity ,Condensed Matter - Strongly Correlated Electrons - Abstract
The recently discovered kagome superconductors $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs) possess a unique band structure with van Hove singularities and Dirac dispersions, in which unusual charge-density-wave (CDW) orders with time-reversal and rotational symmetry breaking have been reported. One of the most crucial unresolved issues is identifying the symmetry of the superconductivity that develops inside the CDW phase. Theory predicts a variety of unconventional superconducting symmetries, including exotic states with chiral and topological properties accompanied by a sign-changing superconducting gap. Experimentally, however, the phase information on the superconducting gap in $A$V$_3$Sb$_5$ is still lacking. Here we report the electron irradiation effects in CsV$_3$Sb$_5$ using introduced impurities as a phase-sensitive probe of superconductivity. Our magnetic penetration depth measurements reveal that with increasing impurities, a highly anisotropic fully-gapped state changes gradually to an isotropic full-gap state without passing through a nodal state. Furthermore, transport measurements under high pressure show that the double superconducting dome in the pressure-temperature phase diagram survives against sufficient impurities. These results are strong bulk evidence that CsV$_3$Sb$_5$ is a non-chiral, anisotropic $s$-wave superconductor with no sign change both at ambient and high pressure, which provides a clue to understanding the relationship between CDW and superconductivity in kagome superconductors., Comment: 22 pages, 4 figures
- Published
- 2022
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