Theory of dissipationless Nernst effects

TL;DR

This paper develops a universal theory for the transverse thermoelectric conductivity x in magnetic fields, linking it to entropy per carrier, with implications for experiments on 2D materials like graphene.

Contribution

It provides an exact, temperature-independent expression for x as entropy per carrier and proves its universality in disordered 2D systems, extending understanding of Nernst effects.

Findings

x equals entropy per carrier for free electrons

Universality of x in disordered 2D systems

Analysis of singularity structure in 3D x(B, T)

Abstract

We develop a theory of transverse thermoelectric (Peltier) conductivity, \alpha_{xy}, in finite magnetic field -- this particular conductivity is often the most important contribution to the Nernst thermopower. We demonstrate that \alpha_{xy} of a free electron gas can be expressed purely and exactly as the entropy per carrier irrespective of temperature (which agrees with seminal Hall bar result of Girvin and Jonson). In two dimensions we prove the universality of this result in the presence of disorder which allows explicit demonstration of a number features of interest to experiments on graphene and other two-dimensional materials. We also exploit this relationship in the low field regime and to analyze the rich singularity structure in \alpha_{xy}(B, T) in three dimensions; we discuss its possible experimental implications.