Anisotropic normal-state transport properties predicted and analyzed for high-Tc oxide superconductors

Abstract

Electronic energy bands calculated from local-density-functional (LDF) theory are used to predict anisotropic transport properties of the oxide superconductors La2−xSrxCuO4 and YBa2Cu3O7. Calculations of the magnitude of the resistivity tensor ραβ (assuming only electron-phonon scattering) lead to results smaller than given by current experiments, suggesting that LDF theory overestimates the Drude plasma frequency (or Fermi velocity), or else that another scattering mechanism dominates. Determinations of the Fermi velocity from critical field measurements suggest however that it is close to the LDF value. Quantities which are independent of the scattering are calculated with more success: the resistivity anisotropy ρzz/ρxx, the Hall tensor Rαβγ’H and the thermopower Sαβ. It is predicted that RH should appear ‘‘holelike’’ when electrons orbit in metallic planes but S should appear ‘‘electronlike’’ for thermal gradients in the plane. When fields are tipped 90°, all coefficients change sign. There is not very much single-crystal data to compare with, but what exists is qualitatively consistent, including anomalous signs of the Hall tensor. Polycrystalline data for RH seem completely at variance with the LDF results, so it is surprising how well single-crystal results agree.

Source-reported materials — not catalogue approval

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