Low-Temperature Thermal Conductivity of the Two-Phase Superconductor CeRh2As2

Abstract

CeRh 2 As 2 is a rare unconventional superconductor ( T c = 0.26 K) characterized by two adjacent superconducting phases for a magnetic field H ‖ c -axis of the tetragonal crystal structure. Antiferromagnetic order, quadrupole-density-wave order ( T 0 = 0.4 K) and the proximity of this material to a quantum-critical point have also been reported: The coexistence of these phenomena with superconductivity is currently under discussion. Here, we present thermal conductivity and electrical resistivity measurements on a single crystal of CeRh 2 As 2 between 60 mK and 200 K and in magnetic fields ( H ‖ c ) up to 8 T. Extrapolation of our normal-state data to zero temperature validates the Wiedemann-Franz law within the error bars. The T dependence of the thermal conductivity κ ( T ) shows a pronounced drop below T c which is also field dependent and thus interpreted as the signature of superconductivity. However, the large residual resistivity and the lack of sharp anomalies in κ ( T ) at the expected transition temperatures clearly indicate that samples of much higher purity are required to gain more information about the superconducting gap structure.