Tomotaka Ochi | Searcharxiv

arXiv2023

Quantized thermoelectric Hall plateau in the quantum limit of graphite as a nodal line semimetal

We performed thermoelectric Hall conductivity $α_{xy}$ measurements on single-crystal graphite in the quantum limit up to 13 T. Both electrical and thermoelectric transport measurements were performed on the same crystal to extract pure $α_{xy}$, avoiding any sample quality dependence. The $α_{xy}$ converges to a plateau in the quantum limit with a linear dependence on temperature. This behavior is analogous to the quantized thermoelectric Hall effect (QTHE) observed in three-dimensional Dirac/Weyl nodal-point semimetals, and experimentally confirms a theoretical proposal on the QTHE in semimetals with nodal lines as in graphite.

cond-mat.mes-hall↗

arXiv2022

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

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.

cond-mat.mes-hall↗