Regensburg 2022 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 22: Unconventional Superconductors

TT 22.5: Talk

Wednesday, September 7, 2022, 16:15–16:30, H10

Thermal conductivity of the two-phase superconductor CeRh₂As₂ — Seita Onishi¹, •Ulrike Stockert¹, Seunghyun Khim¹, Jacintha Banda¹, Manuel Brando¹, and Elena Hassinger^1,2 — ¹MPI for Chemical Physics of Solids, Dresden, Germany — ²Physics Department, Technical University Munich, Germany

CeRh₂As₂ is an unconventional superconductor with T_c = 0.26 K. Two neighbouring superconducting phases are observed for a magnetic field H applied along the c-axis with an almost constant transition field H^⋆ of about 4 T. In addition, antiferromagnetic order, quadrupole-density-wave order and the proximity of this material to a quantum-critical point have been reported: The coexistence of these phenomena with superconductivity is currently under discussion.

We present thermal conductivity, κ, and electrical resistivity, ρ, measured on single crystals of CeRh₂As₂ between 60 mK and 200 K and in magnetic fields (H ∥ c) up to 8 T. The extrapolation of our normal-state data to zero temperature is in line with the Wiedemann-Franz law. No clear anomaly is observed in the temperature dependence of κ at any of the reported phase transitions. Instead, κ(T) shows a pronounced, field-dependent drop below T_c which is attributed to superconductivity. The field-dependence of the normalized thermal conductivity at 120 mK exhibits a change in slope around H^⋆, similar to the specific heat coefficient γ. Measurements at higher fields and lower T are required to confirm that this is really due to the transition between the two superconducting phases.