Lorenz Function of Bi2Te3/Sb2Te3 Superlattices

Combining first-principles density functional theory and semiclassical Boltzmann transport, the anisotropic Lorenz function was studied for thermoelectric Bi2Te3/Sb2Te3 superlattices and their bulk constituents. It was found that, already for the bulk materials Bi2Te3 and Sb2Te3, the Lorenz function is not a clear function of charge carrier concentration and temperature. For electron-doped Bi2Te3/Sb2Te3 superlattices, large oscillatory deviations of the Lorenz function from the metallic limit were found even at high charge carrier concentrations. The latter can be referred to quantum well effects, which occur at distinct superlattice periods.