Transport through a double quantum dot in the sequential- and co- tunneling regimes

TL;DR

This paper investigates electron transport in double quantum dots, revealing how conductance features relate to quantum states and tunneling regimes, and identifies conditions to extract microscopic parameters from experimental data.

Contribution

It provides a detailed analysis of conductance peaks and dips in double quantum dots, connecting microscopic models to observable transport phenomena in different tunneling regimes.

Findings

Satellite peaks in conductance relate to interdot and singlet-triplet splittings.

Temperature regimes allow extraction of Hubbard ratio from cotunneling conductance.

Combined cotunneling and sequential tunneling produce new conductance features.

Abstract

We study transport through a double quantum dot, both in the sequential tunneling and cotunneling regimes. Using a master equation approach, we find that, in the sequential tunneling regime, the differential conductance $G$ as a function of the bias voltage $\Delta\mu$ has a number of satellite peaks with respect to the main peak of the Coulomb blockade diamond. The position of these peaks is related to the interdot tunnel splitting and the singlet-triplet splitting. We find satellite peaks with both {\em positive} and {\em negative} values of differential conductance for realistic parameter regimes. Relating our theory to a microscopic (Hund-Mulliken) model for the double dot, we find a temperature regime for which the Hubbard ratio (=tunnel coupling over on-site Coulomb repulsion) can be extracted from $G(\Delta\mu)$ in the cotunneling regime. In addition, we consider a combined effect of cotunneling and sequential tunneling, which leads to new peaks (dips) in $G(\Delta\mu)$ inside the Coulomb blockade diamond below some temperature scales, which we specify.