Anomalous magnetotransport properties of high-quality single crystals of Weyl semimetal WTe2: Sign change of Hall resistivity

TL;DR

This study investigates the Hall effect in high-quality WTe2 Weyl semimetal crystals, revealing anomalous sign changes in Hall resistivity linked to carrier mobility ratios, Lifshitz transitions, and spin textures.

Contribution

It provides a detailed analysis of carrier densities and mobilities in WTe2, highlighting anomalous Hall resistivity behavior and its possible origins in electronic structure changes.

Findings

Hall resistivity sign changes below 20 K and in low fields

Carrier mobilities approach equality near 20 K

High residual resistivity ratio and magnetoresistance confirm crystal quality

Abstract

We report on a systematic study of Hall effect using high quality single crystals of type-II Weyl semimetal WTe2 with the applied magnetic field B//c. The residual resistivity ratio of 1330 and the large magnetoresistance of 1.5\times10^6 % in 9 T at 2 K, being in the highest class in the literature, attest to their high quality. Based on a simple two-band model, the densities (n_e and n_h) and mobilities (\mu_e and \mu_h) for electron and hole carriers have been uniquely determined combining both Hall- and electrical-resistivity data. The difference between ne and nh is ~1% at 2 K, indicating that the system is in an almost compensated condition. The negative Hall resistivity growing rapidly below ~20 K is due to a rapidly increasing \mu_h/\mu_e approaching one. Below 3 K in a low field region, we found the Hall resistivity becomes positive, reflecting that \mu_h/\mu_e finally exceeds one in this region. These anomalous behaviors of the carrier densities and mobilities might be associated with the existence of a Lifshitz transition and/or the spin texture on the Fermi surface.