# Breakdown of the Wiedemann-Franz law in AB-stacked bilayer graphene

## TL;DR

This paper develops a simple theoretical model for thermoelectric transport in bilayer graphene, revealing how disorder influences the violation of the Wiedemann-Franz law near charge neutrality.

## Contribution

It provides a detailed analysis of thermoelectric properties in bilayer graphene, highlighting the effects of disorder on Wiedemann-Franz law violations, which was less understood compared to single-layer graphene.

## Key findings

- Thermal resistivity approaches zero at charge neutrality without disorder.
- Electric resistivity jumps to a finite value at neutrality.
- Disorder introduces a doping window with strong Wiedemann-Franz law violation.

## Abstract

We present a simple theory of thermoelectric transport in bilayer graphene and report our results for the electrical resistivity, the thermal resistivity, the Seebeck coefficient, and the Wiedemann-Franz ratio as functions of doping density and temperature. In the absence of disorder, the thermal resistivity tends to zero as the charge neutrality point is approached; the electric resistivity jumps from zero to an intrinsic finite value, and the Seebeck coefficient diverges in the same limit. Even though these results are similar to those obtained for single-layer graphene, their derivation is considerably more delicate. The singularities are removed by the inclusion of a small amount of disorder, which leads to the appearance of a "window" of doping densities $0<n<n_c$ (with $n_c$ tending to zero in the zero-disorder limit) in which the Wiedemann-Franz law is severely violated.