Normal and Superconducting Properties of Noncentrosymmetric Heavy Fermion CeRhSi₃

Abstract

We review the normal and superconducting properties in the noncentrosymmetric heavy-fermion CeRhSi 3 . In the normal state, CeRhSi 3 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 CeRhSi 3 . This result is consistent with the theoretical prediction for the noncentrosymmetric superconductor.