Thermoelectric and thermal transport in bilayer graphene systems

TL;DR

This paper investigates how disorder affects thermoelectric and thermal transport in bilayer graphene under magnetic fields, revealing behaviors similar to monolayer graphene and effects of band gap opening.

Contribution

It provides the first detailed numerical analysis of disorder effects on thermoelectric and thermal transport in biased and unbiased bilayer graphene under strong magnetic fields.

Findings

Thermoelectric signals peak at the central Landau level with magnitude ~k_B/e.

Sign change of thermopower occurs near other Landau levels.

Transport properties align with those of a band insulator when a band gap is present.

Abstract

We numerically study the disorder effect on the thermoelectric and thermal transport for bilayer graphene under a strong perpendicular magnetic field. In the unbiased case, we find that the thermoelectric transport has similar properties as in the monolayer graphene, i.e., the Nernst signal has a peak at the central Landau level (LL) with the value of the order of $k_B/e$ and changes sign near other LLs while the thermopower has an opposite behavior. We attribute this to the coexistence of particle and hole LLs around the Dirac point. When a finite interlayer bias is applied and a band gap is opened, it is found that the transport properties are consistent with those of a band insulator. We further study the thermal transport from electronic origins and verify the validity of the generalized Weidemann-Franz law.