Electronic phase coherence vs. dissipation in solid-state quantum devices: Two approximations are better than one

Department of Applied Science and Technology, Politecnico di Torino - C.so Duca degli Abruzzi 24, 10129 Torino, Italy

^(a) fausto.rossi@polito.it

Received: 3 November 2015
Accepted: 22 December 2015

Abstract

In the microscopic modeling of new-generation electronic quantum nanodevices a variety of simulation strategies have been proposed and employed. The aim of this letter is to point out virtues vs. intrinsic limitations of non-Markovian density-matrix approaches; we shall show that the usual mean-field treatment may lead to highly unphysical results, like negative distribution probabilities and non-dissipative behaviours, which are particularly severe in zero-dimensional electronic systems coupled to dispersionless phonon modes. This is in striking contrast with Markovian treatments, where a proper combination of adiabatic limit and mean-field schemes guarantees a physically acceptable solution; as a result, the unusual conclusion is that two approximations are better than one.