Multiband Mechanism for the Sign Reversal of Coulomb Drag Observed in Double Bilayer Graphene Heterostructures

TL;DR

This paper explains the sign reversal of Coulomb drag in double bilayer graphene by highlighting the role of multiband effects, supported by a multiband Fermi liquid theory that matches experimental data across temperatures.

Contribution

It introduces a multiband Fermi liquid theory to explain Coulomb drag sign reversal in double bilayer graphene, emphasizing the significance of multiband effects.

Findings

Multiband effects cause the sign reversal of Coulomb drag.

The multiband Fermi liquid theory matches experimental data.

Multiband effects influence superfluidity and drag in DBLG.

Abstract

Coupled 2D sheets of electrons and holes are predicted to support novel quantum phases. Two experiments of Coulomb drag in electron-hole (e-h) double bilayer graphene (DBLG) have reported an unexplained and puzzling sign reversal of the drag signal. However, we show that this effect is due to the multiband character of DBLG. Our multiband Fermi liquid theory produces excellent agreement and captures the key features of the experimental drag resistance for all temperatures. This demonstrates the importance of multiband effects in DBLG: they have a strong effect not only on superfluidity, but also on the drag.