Strong-Coupling Superconductivity of CeIrSi_3 with the Non-centrosymmetric Crystal Structure(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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We studied the pressure-induced superconductor CeIrSi_3 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 P_c=2.25GPa, where the antiferromagnetic state disappears. The heat capacity C_<ac> shows both antiferromagnetic and super-conducting transitions at pressures close to P_c. On the other hand, the superconducting region is extended to high pressures of up to about 3.5 GPa, with the maximum transition temperature T_<sc>=1.6K around 2.5-2.7GPa. At 2.58GPa, a large heat capacity anomaly was observed at T_<sc>=1.59K. The jump of the heat capacity in the form of ΔC_<ac>/C_<ac>(T_<sc>) 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 T_<sc> is, however, approximately unchanged as a function of pressure, even at P_c.
社団法人日本物理学会の論文
2007-08-15