カゴメ格子超伝導体の非従来型超伝導

抄録

The kagome superconductor AV₃Sb₅ (A = K, Cs, Rb) exhibits unconventional charge-density-wave (CDW) order with broken time-reversal and rotational symmetries. However, the superconducting symmetry remains unclear. We investigate the superconducting state of CsV₃Sb₅ by studying impurity effects through electron irradiation and magnetic penetration depth measurements. We found that non-magnetic impurities change from an anisotropic superconducting gap to an isotropic one without inducing a nodal state. Furthermore, transport measurements under high pressure show that the double superconducting dome persists even after introducing impurities. Our results indicate that CsV₃Sb₅ hosts a non-chiral, anisotropic s-wave superconducting state without sign change of the order parameter both at ambient and under pressure, and supports a new type of unconventional superconductivity due to bond-order fluctuations.