Cotunneling-mediated transport through excited states in the Coulomb blockade regime

TL;DR

This paper investigates inelastic cotunneling and sequential tunneling in a few-electron quantum dot within the Coulomb blockade regime, combining experimental measurements with advanced theoretical calculations to elucidate excited state transport mechanisms.

Contribution

It provides a detailed experimental and theoretical analysis of cotunneling-mediated transport through excited states in quantum dots, employing a real-time Green's function approach up to fourth order.

Findings

Observation of inelastic cotunneling signatures in Coulomb blockade

Identification of sequential tunneling structures after excitation

Agreement between experimental data and theoretical calculations

Abstract

We present finite bias transport measurements on a few-electron quantum dot. In the Coulomb blockade regime, strong signatures of inelastic cotunneling occur which can directly be assigned to excited states observed in the non-blockaded regime. In addition, we observe structures related to sequential tunneling through the dot, occuring after it has been excited by an inelastic cotunneling process. We explain our findings using transport calculations within the real-time Green's function approach, including diagrams up to fourth order in the tunneling matrix elements.