Theory of Thermal Conductivity in High-T_c Superconductors below T_c : Comparison between Hole- and Electron-Doped Systems(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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In hole-doped high-T_c superconductors, thermal conductivity κ increases drastically just below T_c, which has been considered as a hallmark of a nodal gap. In contrast, such a coherence peak in κ is not visible in electron-doped compounds, which may indicate a full-gap state such as a d+is-wave state. To settle this problem, we study κ in the Hubbard model using the fluctuation-exchange (FLEX) approximation, which predicts that the nodal d-wave state is realized in both hole- and electron-doped compounds. The contrasting behavior of κ in both compounds originates from the differences in the hot/cold spot structure. In general, a prominent coherence peak in κ appears in line-node superconductors only when the cold spot exists on the nodal line.
社団法人日本物理学会の論文
2007-07-15