F.Yu, V.N. Kopylov, M.B. Salamon,
N.N. Kolesnikov, M.A. Hubbard, H.M. Duan, A.M. Hermann.
Field dependent thermal conductivity of Tl2Ba2CuO6:
evidence for Andreev scattering of quasiparticles.
We have studied the thermal conductivity of
Tl2Ba2CuO6 (Tl-2201) crystals
as functions of temperature and magnetic field. A thermal conductivity
peak is observed near 0.6 Tc which is greatly reduced
on application of a magnetic field along the c axis. We argue that
the suppression of the peak at relatively low fields (£
8 T<< Hc2) permits us to separate
electronic and phononic contributions. Fields applied in plane are less
effective, but give the same reduction when applied either parallel or
perpendicular to the temperature gradient. A model based on Andreev reflection
by vortex screening currents is shown to be consistent with these results.