Thermal conductivity of an untwinned YBa2Cu3O7- single crystal and a new interpretation of the superconducting state thermal transport

We have measured the anisotropic thermal conductivity of an untwinned single crystal of YBa2Cu3O7- in the most conducting a-b plane from 14 to 200 K. Unlike previous analyses, ours attributes the observed rapid rise in thermal conductivity in the superconducting state to the electronic contribution of the Cu-O plane. We propose that strong suppression of the quasiparticle scattering rate with decreasing temperature is responsible for the large enhancement of the superconducting-state thermal conductivity