Dresden 2026 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 31: Transport in Materials: Diffusion, Charge, or Heat Conduction II

MM 31.8: Talk

Thursday, March 12, 2026, 12:15–12:30, SCH/A216

Interband effects in the matrix Boltzmann transport equation — •Elena Trukhan and Nakib H. Protik — Department of Physics and CSMB, Humboldt University of Berlin

The current state-of-the-art ab initio method for computing electronic transport properties relies on the Boltzmann transport equation (BTE). However, the BTE fails to capture certain quantum effects, most notably interband coherence. To address this limitation for phonon transport, Simoncelli et al [1]. developed an approach based on the Wigner transport equation, which incorporates these effects by including the off-diagonal terms of the density matrix. This framework was later adapted to electrons by Cepellotti and Kozinsky [2]. Their method, however, involves several critical simplifications; for instance, it ignores kinetic corrections and treats the collision integral within a relaxation time approximation (RTA). Also, modern derivations rely on the assumption of a band-diagonal form of the interaction self-energies, which might not hold generally. In this work, we derive a more general electronic transport equation from a Green's function formalism. Using a modified Kadanoff-Baym Ansatz, we carefully track the terms that survive various standard approximations in the Dyson equations in the band representation, explicitly include electron-impurity and electron-phonon interactions, keeping self-energy in non-diagonal form and present a framework that captures interband coherence while moving beyond the RTA.

[1] M. Simoncelli, et al., Phys. Rev. X 12, 041011 (2022) [2] A. Cepellotti and B. Kozinsky, Mater. Today Phys. 19, 100412 (2021)

Keywords: Boltzmann transport equation; Wigner transport equation; Interband coherence