Observation of Giant Nernst plateau in ideal 1D Weyl Phase

TL;DR

This study uncovers a giant, field-independent Nernst plateau in HfTe5, attributed to an ideal 1D Weyl phase, revealing new thermoelectric phenomena and phase transitions in topological materials.

Contribution

It provides the first experimental observation of a giant Nernst plateau linked to an ideal 1D Weyl phase in high magnetic fields.

Findings

Observation of a large Nernst plateau up to 50 μV/K at 2 K.

Identification of magnetic-field-driven phase transitions in HfTe5.

Theoretical explanation linking the plateau to the ideal 1D Weyl phase.

Abstract

The search for a giant Nernst effect beyond conventional mechanisms offers advantages for developing advanced thermoelectric devices and understanding charge-entropy conversion. Here, we study the Seebeck and Nernst effects of HfTe5 over a wide range of magnetic fields. By tracking the unusual magneto-thermoelectric responses, we reveal two magnetic-field-driven phase transitions proposed for weak topological insulators: the gap-closing transition of the zeroth Landau bands and the topological Lifshitz transition. After the magnetic fields exceed approximately ten times the quantum limit, we observe that the Nernst signal no longer varies with the fields, forming a plateau with a remarkably large value, reaching up to 50 {\mu}V/K at 2 K. We theoretically explain the giant Nernst plateau as a unique signature of the ideal 1D Weyl phase formed in such high fields. Our findings expand the understanding of ideal Weyl physics and open new avenues for realizing novel thermoelectric effects without fundamental constraints.