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 magneticshielding 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.

Non-centrosymmetric Heavy-Fermion Superconductors

“…However, this feature observed at P < P * 1 becomes less obvious at P * 3 ≈ 2.6 GPa [72]. An influence of the antiferromagnetic order to explain this unusual curve shape cannot be excluded.…”

“…The coefficient A in CeRhSi 3 is almost constant up to P * 1 [72] and Fig. 17 Temperature dependence of the resistivity of (a) CeRhSi 3 [72], (c) CeIrSi 3 [40] and (d) CeCoGe 3 [43]. (b) Resistivity against T 2 in CeRhSi 3 .…”

“…The temperature-pressure (T -P) phase diagrams of CeRhSi 3 [72], CeIrSi 3 [75], CeCoGe 3 [76] and CeIrGe 3 [42] are shown in Fig. 15.…”

“…16). The heat capacity jump (∆C) at the superconducting transition [72], CeIrSi 3 [75], CeCoGe 3 [77] and CeIrGe 3 [42]. T * in panel (a) denotes an anomaly observed in the resistivity and magneticsusceptibility measurements [39].…”

Theoretical investigation of superconductivity in SrAuSi3 and SrAu2Si2

“…The main reason for these studies is to describe the role of the noncentrosymmetric crystal structure in the formation of unconventional Cooper pairing with nodes in the superconducting gap. Several Ce materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] crystallizing in BaNiSn 3 -type structure have been found to be superconductors, and show interesting physical properties. The majority of Ce materials are antiferromagnetic and become superconducting only under pressure.…”