Quasiclassical Theory for Thermodynamic Properties of the Two-Band Superconductor MgB_2 under Magnetic Fields(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

概要

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Consistent account is provided of strongly anisotropic properties in thermodynamics of MgB_2 under magnetic field H using approximate analytic solution in the quasiclassical formalism. With the strength of the pairing interactions and the Fermi velocities of two bands as fitting parameters, it is possible to reproduce in wide regions of the phase diagram the H- and temperature dependences of relevant quantities such as the zero-energy density of states (ZEDOS), two energy gaps, the specific heat and the H_<c2> anisotropy. It is demonstrated that the velocity ratio of two bands affects considerably the low-field behavior of the ZEDOS and energy gaps. The ratio also affects the high-temperature behavior of the H_<c2> anisotropy. The anisotropy of the coherence length in the σ band depends weakly on H and T, whereas the coherence length in the π band remains isotropic even in the presence of the inter-band coupling.
社団法人日本物理学会の論文
2005-06-15