Influence of Gap Structures to Specific Heat in Oriented Magnetic Fields : Application to the Orbital Dependent Superconductor, Sr_2RuO_4(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

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We discuss influence of modulation of gap function and anisotropy of Fermi velocity to field angle dependences of upper critical field, H_<C2>, and specific heat, C, on the basis of the approximate analytic solution in the quasiclassical formalism. Using four-fold modulation of the gap function and the Fermi velocity in the single-band model, we demonstrate field and temperature dependence of oscillatory amplitude of H_<C2> and C. We apply the method to the effective two-band model to discuss the gap structure of Sr_2RuO_4, focusing on recent field angle-resolved experiments. It is shown that the gap structures with the intermediate magnitude of minima in [100] direction for y band, and tiny minima of gaps in [110] directions for α and β bands give consistent behaviors with experiments. The interplay of the above two gaps also explains the anomalous temperature dependence of in-plane H_<C2> anisotropy, where the opposite contribution from the passive αβ band is pronounced near T_c.
社団法人日本物理学会の論文
2004-09-15