Abstract
A simple and efficient approximation scheme to study electronic transport characteristics of strongly correlated nano devices, molecular junctions or heterostructures out of equilibrium is provided by steady-state cluster perturbation theory. In this work, we improve the starting point of this perturbative, nonequilibrium Green's function based method. Specifically, we employ an improved unperturbed (so-called reference) state $\hat{\rho}^S$, constructed as the steady-state of a quantum master equation within the Born-Markov approximation. This resulting hybrid method inherits beneficial aspects of both, the quantum master equation as well as the nonequilibrium Green's function technique. We benchmark the new scheme on two experimentally relevant systems in the single-electron transistor regime: An electron-electron interaction based quantum diode and a triple quantum dot ring junction, which both feature negative differential conductance. The results of the new method improve significantly with respect to the plain quantum maste equation treatment at modest additional computational cost.
Highlights
Electronic transport in the realm of molecular scale junctions and devices has become a subject of intense study in recent years [1,2,3,4,5,6,7]
The main improvements of master equations (ME)-cluster perturbation theory (CPT) with respect to bare BMS-ME are (i) the inclusion of lead-induced broadening effects, (ii) the correct U = 0 limit, and (iii) a correction for effects missed by an improper treatment of quasidegenerate states in the BMS-ME
For master equation based stsCPT (ME-CPT) based on Born-Markov ME (BM-ME) we find qualitative similar results to ME-CPT based on BMS-ME, which emphasizes the robustness of the ME-CPT results in general
Summary
Electronic transport in the realm of molecular scale junctions and devices has become a subject of intense study in recent years [1,2,3,4,5,6,7]. The controlled assembly of structures [8] via electromigration [9,10,11,12,13,14,15,16,17], the contacting in mechanical break-junction setups [18,19,20,21], electronic gating [17,19,22], and measurement via scanning tunneling microscopy [23,24,25,26] have become established tools, opening routes from elementary understanding to device engineering Prompted by these formidable advances in experimental techniques, the characterization of transport through, e.g., molecules bound by anchor groups to metal electrodes [20,21,27], heterostructures [28,29], or nanostructures on two-dimensional substrates [28,30,31,32,33,34,35] has become feasible. Suitable approximations need to be devised in order to solve a finite strongly correlated quantum many-body
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