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

摘要

The interplay between interference effects and electron-electron interactionsin electron transport through an interacting double quantum dot system isinvestigated using a hierarchical quantum master equation approach whichbecomes exact if carried to infinite order and converges well if thetemperature is not too low. Decoherence due to electron-electron interactionsis found to give rise to pronounced negative differential resistance, enhancedbroadening of structures in current-voltage characteristics and an inversion ofthe electronic population. Dependence on gate voltage is shown to be a usefulmethod of distinguishing decoherence-induced phenomena from effects induced byother mechanisms such as the presence of a blocking state. Comparison ofresults obtained by the hierarchical quantum master equation approach to thoseobtained from the Born-Markov approximation to the Nakajima-Zwanzig equationand from the non-crossing approximation to the nonequilibrium Green's functionreveals the importance of an inter-dot coupling that originates from the energydependence of the conduction bands in the leads and the need for a systematicperturbative expansion.