Decoherence and lead induced inter-dot coupling in nonequilibrium electron transport through interacting quantum dots: A hierarchical quantum master equation approach

TL;DR

This paper investigates how decoherence and lead-induced inter-dot coupling affect electron transport in double quantum dots, revealing phenomena like negative differential resistance and population inversion using a hierarchical quantum master equation approach.

Contribution

It introduces a hierarchical quantum master equation method to accurately analyze decoherence effects and inter-dot coupling in nonequilibrium quantum dot transport.

Findings

Decoherence causes negative differential resistance.

Inter-dot coupling from lead conduction band energy dependence is significant.

Gate voltage helps distinguish decoherence effects from other mechanisms.

Abstract

The interplay between interference effects and electron-electron interactions in electron transport through an interacting double quantum dot system is investigated using a hierarchical quantum master equation approach which becomes exact if carried to infinite order and converges well if the temperature is not too low. Decoherence due to electron-electron interactions is found to give rise to pronounced negative differential resistance, enhanced broadening of structures in current-voltage characteristics and an inversion of the electronic population. Dependence on gate voltage is shown to be a useful method of distinguishing decoherence-induced phenomena from effects induced by other mechanisms such as the presence of a blocking state. Comparison of results obtained by the hierarchical quantum master equation approach to those obtained from the Born-Markov approximation to the Nakajima-Zwanzig equation and from the non-crossing approximation to the nonequilibrium Green's function reveals the importance of an inter-dot coupling that originates from the energy dependence of the conduction bands in the leads and the need for a systematic perturbative expansion.