Thermoelectric energy conversion in molecular junctions out of equilibrium

TL;DR

This paper develops a non-equilibrium Green's function approach using the $i$GKBA method to study time-dependent thermoelectric transport in molecular junctions, emphasizing finite-bandwidth effects and providing benchmarks against full Kadanoff-Baym theory.

Contribution

It introduces a novel $i$GKBA-based formalism for modeling ultrafast thermoelectric transport beyond the wide-band limit in molecular junctions.

Findings

Finite-bandwidth effects are crucial for accurate thermoelectric modeling.

The $i$GKBA approach efficiently captures time-resolved thermoelectric phenomena.

Benchmark comparisons validate the method against full Kadanoff-Baym calculations.

Abstract

Understanding time-resolved quantum transport is crucial for developing next-generation quantum technologies, particularly in nano- and molecular junctions subjected to time-dependent perturbations. Traditional steady-state approaches to quantum transport are not designed to capture the transient dynamics necessary for controlling electronic behavior at ultrafast time scales. In this work, we present a non-equilibrium Green's function formalism, within the recently-developed iterated generalized Kadanoff-Baym ansatz ($i$GKBA), to study thermoelectric quantum transport beyond the wide-band limit approximation (WBLA). We employ the Meir-Wingreen formula for both charge and energy currents and analyze the transition from Lorentzian line-width functions to the WBLA, identifying unphysical divergences in the latter. Our results highlight the importance of finite-bandwidth effects and demonstrate the efficiency of the $i$GKBA approach in modeling time-resolved thermoelectric transport, also providing benchmark comparisons against the full Kadanoff-Baym theory. We exemplify the developed theory in the calculation of time-resolved thermopower and thermoelectric energy conversion efficiency in a cyclobutadiene molecular junction.