Coulomb drag and counterflow Seebeck coefficient in bilayer-graphene double layers

TL;DR

This study investigates Coulomb drag and counterflow thermoelectric effects in bilayer graphene double layers separated by boron nitride, revealing significant potential for lightweight thermoelectric applications and tunable interlayer interactions.

Contribution

It provides experimental measurements of Coulomb drag and counterflow Seebeck coefficients in bilayer graphene heterostructures, highlighting their thermoelectric performance and tunability.

Findings

Coulomb drag resistivity is much smaller than intralayer resistivities.

Counterflow Seebeck coefficient peaks when layers have opposite charge carriers.

Maximum power factor around 700 μW/K²cm at room temperature.

Abstract

We have fabricated bilayer-graphene double layers separated by a thin ($\sim$20 nm) boron nitride layer and performed Coulomb drag and counterflow thermoelectric transport measurements. The measured Coulomb drag resistivity is nearly three orders smaller in magnitude than the intralayer resistivities. The counterflow Seebeck coefficient is found to be well approximated by the difference between Seebeck coefficients of individual layers and exhibit a peak in the regime where two layers have opposite sign of charge carriers. The measured maximum counterflow power factor is $\sim$ 700 $\mu$W/K$^2$cm at room temperature, promising high power output per mass for lightweight thermoelectric applications. Our devices open a possibility for exploring the novel regime of thermoelectrics with tunable interactions between n-type and p-type channels based on graphene and other two-dimensional materials and their heterostructures.