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As a recently discovered Ce-based 122-type heavy-fermion superconductor, CeRh2As2 has attracted significant attention due to its non-Fermi-liquid behavior and two-phase superconductivity. The tetragonal crystal structure of CeRh2As2 maintains global centrosymmetry which allows even-parity and odd-parity superconducting states to be distinct rather than mixed. The Ce site exhibits local inversion symmetry breaking which enables staggered Rashba spin-orbit coupling. This may lead to the c axis field-induced transition between two superconducting phases and high critical field. Given the novel physics in CeRh2As2, including a possible quantum critical point and a spin-fluctuation-mediated superconducting pairing mechanism, this work investigates the ultra-low-temperature electrical and thermal transport properties of CeRh2As2 under various magnetic fields. The zero-field resistivity reveals a superconducting transition at the critical temperature Tc = 0.34 K. Under 1 T magnetic field, a resistivity minimum emerges near T0≈0.42 K, likely arising from partial gap opening due to Fermi surface nesting, indicating the system enters into a magnetically ordered state, while this feature isn’t observed in zero field. In the temperature range from T0 to 2 K, the system exhibits non-Fermi-liquid behavior ρ~T0.44, suggesting proximity to a quantum critical point. The superconducting transition is fully suppressed at 7 T, with resistivity recovering Fermi-liquid behavior at low temperature. No significant anomaly is observed near Tc in the zero-field thermal conductivity of CeRh2As2. This absence of anomaly may be attributed to the high residual resistivity of the sample, and the reduction in carrier density during the superconducting transition and the T0 phase transition. It requirs optimizing single crystal growth to reduce the effects of lattice defects or chemical disorder on thermal transport. Upon applying magnetic field, the thermal conductivity curve exhibits a small upward shift relative to its zero-field curve. At 0.15 K, thermal conductivity rises with increasing magnetic field and saturates at higher fields above 5 T. In the normal state at 7 T, we find that the electrical resistivity and thermal conductivity satisfy the Wiedemann-Franz law, indicating that the charge and heat transport are governed by the same quasiparticles, consistent with the Fermi-liquid behavior observed in resistivity under this field.
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Keywords:
- Heavy-fermion superconductor /
- CeRh2As2 /
- Electrical resistivity /
- Ultra-low-temperature thermal conductivity
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