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

Abstract

CeRh2As2 is a rare unconventional superconductor (Tc = 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 (T0 = 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 CeRh2As2 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 Tc 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.

Field-angle dependence reveals odd-parity superconductivity in CeRh$_2$As$_2$

“…It was suggested that this is due to percolating strain-induced superconductivity around impurities. Experimentally, the resistive T c follows the bulk T c in a parallel fashion for both H c and H a [9,19]. While the angle dependence of the superconducting state could have been investigated by resistivity as well, the transition at H * is invisible to this probe [8,9,19].…”

Parity Transition of Spin-Singlet Superconductivity Using Sublattice Degrees of Freedom

“…This is the first experimental indication of the SC parity transition originating from the sublattice degrees of freedom and has promoted many theoretical studies [7][8][9][10][11][12][13]. However, to date, there have been few experimental investigations on the SC properties [14][15][16]. Therefore, further experimental confirmation is required.…”

Horizontal flux growth as an efficient preparation method of CeRh2As2 single crystals

“…The discovery of multi-phase superconductivity in CeRh 2 As 2 1 turned the eyes of many solid-state researchers toward this compound and made it almost instantly one of the most highlighted materials of recent times. In consequence, numerous papers, both experimental 1–7 and theoretical, 8–16 have been published in the last few years. The most remarkable features of this material are related to the phase transition within the superconducting state, which occurs upon applying a magnetic field along the c -axis and leads to an extraordinarily distinct violation of the Pauli-Clogston limit.…”