Large heat capacity jump at the superconducting transiton temperature in the non-centrosymmetric superconductor CeIrSi_(3) under high pressure.

摘要

We investigated the pressure-induced superconductor CeIrSi_(3) without inversion center under high pressure. The electrical resistivity and ac heat capacity were measured in the same run for the same sample. The critical pressure of the antiferromagnetic state was determined to be P_(c) velence 2.25 GPa. The heat capacity C_(ac) shows both antiferromagnetic and superconducting transitions at pressures close to P_(c). The co-existence of the antiferromagnetism and superconductivity is discussed. The superconducting region is extended up to about 3.5 GPa. The superconducting transition temperature T_(sc) shows a maximum value of 1.6 K around 2.5- 2.7 GPa. At 2.58 GPa, a large heat capacity anomaly was observed at T_(sc) velence 1.59 K. The jump of the heat capacity in the form of (DELTA)C_(ac)/C_(ac)(T_(sc)) is 5.7 +- 0.1. This is the largest observed value among all superconductors studied previously, suggesting the strong-coupling superconductivity in CeIrSi_(3).