Memory-function approach for electronic transport in disordered solids

We present an ab initio method for the evaluation of transport coefficients from electronic-structure calculations which goes beyond the relaxation-time approximation. We focus on the electrical conductivity that within the Kubo linear response theory is related to the current-current correlation function. We evaluate this correlation with a memory function approach including scattering processes to infinite order. We have implemented this method in the exciting code [1]. It only requires the non-interacting space- and time-dependent charge-charge correlation function and a description of the scattering mechanism. As a proof of principle, we calculate the conductivity of sodium limited by static disorder. The self-consistent approach describes the localization of the carriers in this simple metal for strong disorder. In comparison with the relaxation-time approximation, our method captures the Anderson localization of the system and corrects the overestimation of the conductivity in the metallic phase.

[1] Gulans et al., J. Phys.: Condens. Matter 26, 363202 (2014).