TRACK: A python code for calculating the transport properties of correlated electron systems using Kubo formalism

Abstract

Exploring the transport properties of different materials brings new avenue for basic understanding of emergent phenomena and practical applications in many different fields. Here, we report a program named as TRACK (TRAnsport properties for Correlated materials using Kubo formalism) which is written in Python 3 for calculating temperature dependent electrical conductivity, electronic part of thermal conductivity, Seebeck coefficient and Lorenz number. In this code, Kubo linear-response formalism is utilized for computing these parameters using both interacting and non-interacting electronic structure methods. The formula for transport coefficients is accordingly modified to obtain the transport parameters under relaxation time approximation using band-theory. The basic inputs of this program are the structural information, dense k-points sampling in the irreducible part of the Brillouin zone and the information of velocity matrix elements, which can be calculated using third-party ab-initio package. TRACK is expected to calculate the transport properties of different class of materials. The code has been benchmarked by performing calculation on three different types of materials namely Vanadium (V), FeSi and LaCoO3, which are metal, semiconductor and Mott insulator, respectively. The temperature dependent behaviour of the transport coefficients for these materials show fairly good agreement with the corresponding experimental data.

LinReTraCe: The Linear Response Transport Centre

“…This approximation is warranted as the self-energy typically varies slowly inside the narrow energy-window probed by transport (a few k B T ). 1 Following common practice of Kubo implementations [35][36][37][42][43][44][45][46][47][48][49], LinReTraCe neglects particle-hole scattering, so-called vertex corrections. 2 The ensuing analytical transport functions are then not only numerically inexpensive and stable, they also reveal valuable microscopic information: In particular they show that the scattering is not a mere prefactor (scaling the amplitude of conduction), but a relevant energy scale that has a complex interplay with other energies of the system, e.g., the charge gap in a semiconductor [2].…”