Bulk evidence of anisotropic s-wave pairing with no sign change in the kagome superconductor CsV3Sb5
M. Roppongi, K. Ishihara, Y. Tanaka, Kensuke Ogawa, Keisuke Okada, S. Liu, Kiyotaka Mukasa, Yuta Mizukami, Yoshiya Uwatoko, Romain Grasset, M. Kończykowski, Brenden R. Ortiz, Stephen D. Wilson, K. Hashimoto, T. Shibauchi
Abstract
Abstract The recently discovered kagome superconductors A V 3 Sb 5 ( A = K, Rb, Cs) exhibit unusual charge-density-wave (CDW) orders with time-reversal and rotational symmetry breaking. 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 with sign-changing and chiral order parameters. Experimentally, however, superconducting phase information in A V 3 Sb 5 is still lacking. Here we report the impurity effects in CsV 3 Sb 5 using electron irradiation as a phase-sensitive probe of superconductivity. Our magnetic penetration depth measurements reveal that with increasing impurities, an anisotropic fully-gapped state changes to an isotropic full-gap state without passing through a nodal state. Furthermore, transport measurements under pressure show that the double superconducting dome in the pressure-temperature phase diagram survives against sufficient impurities. These results support that CsV 3 Sb 5 is a non-chiral, anisotropic s -wave superconductor with no sign change both at ambient and under pressure.