Dissipative quantum transport at arbitrary parameter regime: a variational method

TL;DR

This paper introduces a variational method based on polaron theory to accurately model dissipative quantum transport across all electron-phonon coupling regimes, filling a gap in existing theories.

Contribution

A novel variational approach employing optimal polaron transformation for dissipative quantum transport at any coupling strength.

Findings

Accurately models quantum transport for arbitrary electron-phonon coupling.

Employs variational free energy minimization for optimal transformation.

Validated with numerical benchmarks on a single-site model.

Abstract

Recent development of theoretical method for dissipative quantum transport have achieved notable progresses in the weak or strong electron-phonon coupling regime. However, a generalized theory for dissipative quantum transport at arbitrary parameter regime is not figured out until now. In this work, a variational method for dissipative quantum transport at arbitrary electron-phonon coupling regime is developed by employing variational polaron theory. The optimal polaron transformation is determined by the optimization of the Feynman-Bogoliubov upper bound of free energy. % which is variational in nature. The free energy minimization ends up with an optimal mean-field Hamiltonian and a minimal interaction Hamiltonian. Hence, second-order perturbation can be applied to the transformed system, resulting an accurate and efficient method for the treatment of dissipative quantum transport with arbitrary electron-phonon coupling strength. Numerical benchmark calculation on an single site model with coupling to one phonon mode is also presented.