Normal and Superconducting Properties of Noncentrosymmetric Heavy Fermion CeRhSi₃

Abstract

We review the normal and superconducting properties in the noncentrosymmetric heavy-fermion CeRhSi₃. In the normal state, CeRhSi₃ exhibits the antiferromagnetic order at low temperatures (1.6 K at ambient pressure) although its Kondo temperature is much higher than the ordering temperature T_N. With applying pressure P, T_N initially increases and subsequently decreases. The superconductivity arises at the pressures where the antiferromagnetic transition occurs. T_N does not seem to fall to zero but becomes nearly constant with further application of pressure, and then T_N vs P merges with the superconducting transition temperature T_c vs P at 26 kbar where T_c reaches the maximum. Nearly perfect magnetic-shielding associated with the superconductivity is observed below 26 kbar, suggesting that the bulk superconductivity is realized below T_N. We observe an anomaly below T_c in the resistivity as well as in the ac-susceptibility. The origin of the both anomalies seem to be the same but have not been clarified. The magnetic field–temperature (H–T) phase diagram of the superconducting state for fields along the tetragonal a-axis is unusual. It has a concave structure and the upper-critical-field H_c2 at zero temperature exceeds the paramagnetic limiting field expected from the BCS model. The pressure dependence of H–T phase diagram implies that the paramagnetic effect exists and the effect is much reduced in CeRhSi₃. This result is consistent with the theoretical prediction for the noncentrosymmetric superconductor.