Lorenz function of Bi2Te3/Sb2Te3 superlattices

Combining first principles density functional theory and semi-classical 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 pellucid function on charge carrier concentration and temperature. For electron-doped Bi2Te3/Sb2Te3 superlattices large oscillatory deviations for 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.