Inelastic cotunneling in quantum dots and molecules with weakly broken degeneracies

TL;DR

This paper investigates inelastic cotunneling in quantum dots and molecules with weakly broken degeneracies, revealing characteristic gate-dependent conductance behaviors using a rate equation and T-matrix formalism.

Contribution

It introduces a detailed analysis of inelastic cotunneling in systems with weak degeneracy breaking, highlighting the asymmetric gate dependence of conductance.

Findings

Conductance decreases after inelastic threshold on one side of Coulomb diamond.

Conductance increases monotonously after threshold on the other side.

Asymmetric gate voltage dependence of effective cotunneling amplitudes explains observed behavior.

Abstract

We calculate the nonlinear cotunneling conductance through interacting quantum dot systems in the deep Coulomb blockade regime using a rate equation approach based on the T-matrix formalism, which shows in the concerned regions very good agreement with a generalized master equation approach. Our focus is on inelastic cotunneling in systems with weakly broken degeneracies, such as complex quantum dots or molecules. We find for these systems a characteristic gate dependence of the non-equilibrium cotunneling conductance. While on one side of a Coulomb diamond the conductance decreases after the inelastic cotunneling threshold towards its saturation value, on the other side it increases monotonously even after the threshold. We show that this behavior originates from an asymmetric gate voltage dependence of the effective cotunneling amplitudes.