Coulomb drag in quantum circuits

TL;DR

This paper investigates Coulomb drag effects in coupled quantum point contacts, revealing how drag current peaks at conductance transitions and can serve as a tool to measure quantum shot noise, even at low voltages.

Contribution

It provides a detailed analysis of Coulomb drag in quantum circuits, linking drag behavior to conductance quantization and shot noise, with implications for noise measurement techniques.

Findings

Drag current peaks at conductance transitions.

Drag current proportional to shot noise in non-linear regime.

Transition to non-linear regime occurs at voltages below temperature.

Abstract

We study drag effect in a system of two electrically isolated quantum point contacts (QPC), coupled by Coulomb interactions. Drag current exhibits maxima as a function of QPC gate voltages when the latter are tuned to the transitions between quantized conductance plateaus. In the linear regime this behavior is due to enhanced electron-hole asymmetry near an opening of a new conductance channel. In the non-linear regime the drag current is proportional to the shot noise of the driving circuit, suggesting that the Coulomb drag experiments may be a convenient way to measure the quantum shot noise. Remarkably, the transition to the non-linear regime may occur at driving voltages substantially smaller than the temperature.