Engineering drag currents in Coulomb coupled quantum dots

TL;DR

This paper investigates quantum coherent Coulomb drag in double quantum dots with strong interactions, showing how tunneling engineering can control current direction and type, revealing new quantum transport phenomena.

Contribution

It introduces a model where cotunneling enables drag currents in strongly interacting quantum dots, highlighting quantum coherence effects and current control via tunneling engineering.

Findings

Quantum coherent drag occurs with large Coulomb interactions.

Tunneling probabilities can be engineered to control current direction.

Drag current can be manipulated by gate potential, switching between electron and hole transport.

Abstract

The Coulomb drag phenomenon in a Coulomb-coupled double quantum dot system is revisited with a simple model that highlights the importance of simultaneous tunneling of electrons. Previously, cotunneling effects on the drag current in mesoscopic setups have been reported both theoretically and experimentally. However, in both cases the sequential tunneling contribution to the drag current was always present unless the drag level position were too far away from resonance. Here, we consider the case of very large Coulomb interaction between the dots, whereby the drag current needs to be assisted by cotunneling events. As a consequence, a quantum coherent drag effect takes place. Further, we demonstrate that by properly engineering the tunneling probabilities using band tailoring it is possible to control the sign of the drag and drive currents, allowing them to flow in parallel or antiparallel directions. We also show that the drag current can be manipulated by varying the drag gate potential and is thus governed by electron- or hole-like transport.