Kinetic theory of Coulomb drag in two monolayers of graphene: from the Dirac point to the Fermi liquid regime

TL;DR

This paper provides a comprehensive theoretical analysis of Coulomb drag in dual graphene monolayers, exploring various regimes from charge neutrality to Fermi liquid, revealing complex temperature and distance dependencies with implications for future experiments.

Contribution

It introduces a unified Boltzmann equation framework to analyze Coulomb drag across different regimes in graphene monolayers, highlighting new temperature and distance scaling behaviors.

Findings

Presence of passive layer influences active layer conductivity near neutrality.

Drag resistivity varies with inelastic and elastic scattering ratios.

Identification of two regimes with different distance and temperature dependencies.

Abstract

We theoretically investigate Coulomb drag in a system of two parallel monolayers of graphene. Using a Boltzmann equation approach we study a variety of limits ranging from the non-degenerate interaction dominated limit close to charge neutrality all the way to the Fermi liquid regime. In the non-degenerate limit we find that the presence of the passive layer can largely influence the conductivity of the active layer despite the absence of drag. This induces a non-trivial temperature behavior of the single layer conductivity and furthermore suggests a promising strategy towards increasing the role of inelastic scattering in future experiments. For small but finite chemical potential we find that the drag resistivity varies substantially as a function of the ratio of inelastic and elastic scattering. We find that an extrapolation from finite chemical potential to zero chemical potential and to the clean system is delicate and the order of limits matters. In the Fermi liquid regime we analyze drag as a function of temperature $T$ and the distance $d$ between the layers and compare our results to existing theoretical and experimental results. In addition to the conventional $1/d^4$-dependence with an associated $T^2$-behavior we find there is another regime of $1/d^5$-dependence where drag varies in linear-in-$T$ fashion. The relevant parameter separating these two regimes is given by $\bar{d}=T d/v_F$ ($v_F$ is the Fermi velocity), where $\bar{d} \ll1$ corresponds to $T^2$-behavior, while $\bar{d}\gg1$ corresponds to $T$-behavior.