The thermopower and Nernst Effect in graphene in a magnetic field

TL;DR

This paper investigates the thermopower and Nernst effect in graphene under magnetic fields, revealing quantum oscillations, agreement with edge-current models, and unique features at the Dirac point.

Contribution

It provides experimental measurements of thermoelectric effects in graphene in magnetic fields, confirming theoretical models and highlighting unique behaviors at the Dirac point.

Findings

Quantum oscillations in thermopower and Nernst signal with gate voltage.

Quantitative agreement with the edge-current model for Landau levels n ≠ 0.

Enhanced Nernst signal and narrow peak at the Dirac point.

Abstract

We report measurements of the thermopower $S$ and Nernst signal $S_{yx}$ in graphene in a magnetic field $H$. Both quantities show strong quantum oscillations vs. the gate voltage $V_g$. Our measurements for Landau Levels of index $n\ne 0$ are in quantitative agreement with the edge-current model of Girvin and Jonson (GJ). The inferred off-diagonal thermoelectric conductivity $\alpha_{yx}$ comes close to the quantum of Amps per Kelvin. At the Dirac point ($n=0$), however, the width of the peak in $\alpha_{yx}$ is very narrow. We discuss features of the thermoelectric response at the Dirac point including the enhanced Nernst signal.