Quasiparticle transport belowTcin the cuprate superconductors

Abstract

The interpretation of experimental data on the Nernst and Seebeck effects in the mixed state of a type-II superconductor requires a careful treatment of the temperature-dependent electrothermal conductivity ${S}_{n}(T)/{\ensuremath{\rho}}_{n}(T)$ below ${T}_{c}$ (${S}_{n}=\mathrm{Seebeck}\mathrm{}\mathrm{coefficient},$ ${\ensuremath{\rho}}_{n}=\mathrm{resistivity}$). For the cuprate superconductors such as ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}},$ a simple extrapolation from the normal-state behavior above ${T}_{c}$ is inadequate and can lead to erroneous results, due to the opening of the superconducting energy gap and its effect on the temperature dependence of the quasiparticle scattering rate. In particular, the value of the thermal Hall angle of vortex motion depends sensitively on the correct treatment of the electrothermal conductivity below ${T}_{c}.$ Taking experimental data for ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ films as an example, we show that the thermal Hall angle of vortex motion obtained from the data attains the expected small value only if the opening of the energy gap below ${T}_{c}$ is taken into account.