Appearance of anisotropic non s-wave superconductivity above the critical pressure of antiferromagnetic CeRhIn5

Abstract

We have carried out 115In nuclear quadrupole resonance (NQR) measurements in CeRhIn5. At ambient pressure, CeRhIn5 undergoes an antiferromagnetic AF phase transition at \(\) K. The 115In NQR spectrum has shown the appearance of a small internal field in the direction perpendicular to the tetragonal c-axis. With application of a hydrostatic pressure, the AF state is suppressed and the superconductivity appears just above the critical pressure (P = 17 kbar). The nuclear spin lattice relaxation rate 1/T1 of 115In measured at P = 27 kbar indicates the occurrence of the superconductivity in the nearly AF region. In the superconducting state, 1/T1 has no Hebel-Slichter coherence peak just below \(\) of 2 K and has a power law T-dependence (T3) down to 300 mK. This is consistent with anisotropic superconductivity, with line nodes in the superconducting energy gap: non-s-wave superconductivity occurs in CeRhIn5.