Nernst effect and dimensionality in the quantum limit

TL;DR

This study investigates how the Nernst effect in graphite varies with electronic dimensionality, revealing sharp peaks at Landau level crossings that indicate topological Fermi surface changes in the quantum limit.

Contribution

It establishes a direct link between electronic dimensionality and Nernst response, highlighting the role of interlayer coupling in thermoelectric behavior near the quantum limit.

Findings

Nernst signal peaks at Landau level crossings in graphite.

Finite interlayer coupling enhances thermoelectric response.

Landau quantization causes topological Fermi surface changes.

Abstract

Nernst effect, the transverse voltage generated by a longitudinal thermal gradient in presence of magnetic field has recently emerged as a very sensitive, yet poorly understood, probe of electron organization in solids. Here we report on an experiment on graphite, a macroscopic stack of graphene layers, which establishes a fundamental link between dimensionality of an electronic system and its Nernst response. In sharp contrast with single-layer graphene, the Nernst signal sharply peaks whenever a Landau level meets the Fermi level. This points to the degrees of freedom provided by finite interlayer coupling as a source of enhanced thermoelectric response in the vicinity of the quantum limit. Since Landau quantization slices a three-dimensional Fermi surface, each intersection of a Landau level with the Fermi level modifies the Fermi surface topology. According to our results, the most prominent signature of such a topological phase transition emerges in the transverse thermoelectric response.