Magnetic and Superconducting Properties of LaIrSi_3 and CeIrSi_3 with the Non-centrosymmetric Crystal Structure(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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Single crystals of LaIrSi_3 and CeIrSi_3 were grown by the Czochralski pulling method in a tetra-arc furnace and the magnetic and superconducting properties, together with superconductivity in CeIr_<1-x>Co_xSi_3, were clarified by measuring the electrical resistivity, specific heat, magnetic susceptibility, magnetization and de Haas-van Alphen (dHvA) effect. From the results of the dHvA experiment for LaIrSi_3, the Fermi surface is found to split into two Fermi surfaces due to the spin-orbit interaction arising from the non-centrosymmetric crystal structure, which are separated by about 1000K. Similar split Fermi surfaces are expected in the antiferromagnet CeIrSi_3. The electronic state of CeIrSi_3 is tuned from the antiferromagnetic state to the superconducting state by applying pressure. The upper critical field H_<c2>(0) at a pressure of 2.65 GPa is found to be highly anisotropic: H_<c2>(0)=95 kOe for H‖[110] and H_<c2>(0)[〜!-]300kOe for H‖[001], with the superconducting transition temperature T_<sc>[〜!-]1.6K. The large magnitude and anisotropy of H_<c2>(0) in CeIrSi_3 are consistent with the theoretical prediction for superconductivity in the non-centrosymmetric crystal structure. Superconductivity is also observed at ambient pressure in CeIr_<1-x>Co_xSi_3.
2007-04-15