Huge Upper Critical Field and Electronic Instability in Pressure-induced Superconductor CeIrSi_3 without Inversion Symmetry in the Crystal Structure(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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We measured low-temperature electrical resistivity in a magnetic field as a function of pressure, and studied the superconducting property of CeIrSi_3 with a non-centrosymmetric tetragonal structure. CeIrSi_3 is an antiferromagnet with a Neel temperature T_N=5.0K at ambient pressure, but the antiferromagnetic ordering disappears completely at a pressure P_c=2.25GPa. Superconductivity appears in a wide pressure region from 1.8 to about 3.5GPa, with a maximum transition temperature T_<sc>≃1.6K at P^*_c≃2.63GPa. At around P^*_c, the upper critical field H_<c2> for the magnetic field H along the [001] direction is not destroyed by spin polarization based on Zeeman coupling but possesses an upturn curvature below 1K, revealing a divergent tendency of H_<c2> at P^*_c, with a huge H_<c2>(0)≃450kOe. On the other hand, the upper critical field for H‖[110] indicates the tendency of Pauli paramagnetic suppression, with H_<c2>(0)=95kOe at 2.65GPa. This might be a combined phenomenon between the electronic instability at P^*_c and the characteristic superconducting property without inversion symmetry in the tetragonal structure.
社団法人日本物理学会の論文
2008-07-15