Thermoelectric Hall Effect at High-Magnetic-Field Quantum Limit in Graphite as a Nodal-Line Semimetal

TL;DR

This study demonstrates that bulk graphite, a nodal-line semimetal, exhibits the quantized thermoelectric Hall effect under high magnetic fields, with potential for high-performance thermoelectric applications, and explores its dimensional crossover in thin films.

Contribution

It shows that nodal-line semimetals like graphite can exhibit the QTHE, expanding the class of materials known for this effect beyond Dirac/Weyl semimetals.

Findings

Graphite exhibits the quantized thermoelectric Hall effect under high magnetic fields.

Dimensional crossover to 2D thermoelectric behavior observed in thin-film graphite.

Potential for high-performance thermoelectric devices at low temperatures.

Abstract

The high-magnetic-field thermoelectric effect in nodal-line semimetals with straight nodal lines was investigated. Three-dimensional (3D) Dirac/Weyl semimetals exhibit constant thermoelectric Hall conductivity at the high-magnetic-field quantum limit, resulting in a boundless linear increase of Seebeck coefficient. This is known as the quantized thermoelectric Hall effect (QTHE), and is expected to lead to high-performance thermoelectricity at low temperatures. Here, in addition to Dirac/Weyl semimetals, we demonstrated that 3D semimetals with straight nodal lines can also exhibit the QTHE under high magnetic fields. As a candidate material for experimental validation, we discussed the thermoelectric properties of bulk graphite. Furthermore, we investigated the dimensional crossover of thermoelectricity to two-dimensional behavior in thin-film graphite.