抄録
We studied the pressure-induced superconductor CeIrSi3 with the non-centrosymmetric tetragonal structure under high pressure. The electrical resistivity and ac heat capacity were measured in the same run for the same sample. The critical pressure was determined to be Pc=2.25 GPa , where the antiferromagnetic state disappears. The heat capacity Cac shows both antiferromagnetic and superconducting transitions at pressures close to Pc. On the other hand, the superconducting region is extended to high pressures of up to about 3.5 GPa, with the maximum transition temperature Tsc=1.6 K around 2.5–2.7 GPa. At 2.58 GPa, a large heat capacity anomaly was observed at Tsc=1.59 K. The jump of the heat capacity in the form of ΔCac⁄Cac(Tsc) is 5.7±0.1. This is the largest observed value among previously reported superconductors, indicating the strong-coupling superconductivity. The electronic specific heat coefficient at Tsc is, however, approximately unchanged as a function of pressure, even at Pc.
