Angle Dependence of the Transverse Thermal Conductivity in YBa2Cu3O7 Single Crystals: Doppler Shift and Andreev Scattering Contributions

Phys. Rev. Lett. 87, 167006 (2001)

R. Ocaña and P. Esquinazi

Abstract

We have measured the transverse thermal conductivity κxy of twinned and untwinned YBa2Cu3O7 single crystals as a function of angle θ between the magnetic field applied parallel to the CuO2 planes and the heat current direction. For both crystals we observed a clear twofold variation in the field-angle dependence of κxy(θ) = -κxy0(T,B)sin(2θ). We have found that the oscillation amplitude κxy0 depends on temperature and magnetic field. Our results show that κxy0 = aBln(1/bB) with the temperature- and sample-dependent parameters a and b. We discuss our results in terms of Andreev scattering of quasiparticles by vortices and a recently proposed theory based on the Doppler shift in the quasiparticle spectrum.