Transport theory within a generalized Boltzmann equation for multiband wave packets

A generalized theory for transport under applied electrochemical potential and temperature gradients that includes multiband effects is presented. This theory relies on a newly defined density operator for multiband wave packets, whose dynamics containing diffusive and scattering contributions are captured in a generalized equation of motion. Given that the multiband energy structure determines the transport explicitly, the case of N degenerate bands within an isotropic constant relaxation time is considered as a particular case for illustration. Electric and thermal currents as well as transport properties are obtained through linear response and comparison to transport in a single band wave packet is provided. Our theory opens avenues for studying novel multiband effects and scattering processes in transport beyond the semiclassical single band approach.