Quantum oscillations, thermoelectric coefficients and the Fermi surface of semi-metallic WTe2

TL;DR

This study investigates quantum oscillations and thermoelectric properties of semi-metallic WTe2, revealing its complex Fermi surface, carrier dynamics, and unique magnetic breakdown phenomena, with implications for understanding its large magnetoresistance.

Contribution

The paper provides detailed characterization of WTe2's Fermi surface, carrier parameters, and magnetic breakdown effects, highlighting its unique thermoelectric response in high magnetic fields.

Findings

Fermi surface consists of two pairs of electron and hole pockets

Observation of magnetic breakdown frequency above a threshold field

Nernst signal remains linear in magnetic field at high fields

Abstract

We present a study of angle-resolved quantum oscillations of electric and thermoelectric transport coefficients in semi-metallic WTe$_{2}$, which has the particularity of displaying a large B$^{2}$ magneto-resistance. The Fermi surface consists of two pairs of electron-like and hole-like pockets of equal volumes in a "Russian doll" structure. Carrier density, Fermi energy, mobility and the mean-free-path of the system are quantified. An additional frequency is observed above a threshold field and attributed to magnetic breakdown across two orbits. In contrast to all other dilute metals, the Nernst signal remains linear in magnetic field even in the high-field ($\omega_c\tau \gg 1$) regime. Surprisingly, none of the pockets extend across the c-axis of the first Brillouin zone, making the system a three-dimensional metal with moderate anisotropy in Fermi velocity yet a large anisotropy in mean-free-path.