Hall effect in the extremely large magnetoresistance semimetal WTe$_2$

TL;DR

This study investigates the Hall effect in WTe$_2$, revealing temperature-induced changes in carrier densities and suggesting a link to its large magnetoresistance, with evidence of electronic structure modifications at low temperatures.

Contribution

The paper provides detailed temperature-dependent measurements of carrier densities and mobilities in WTe$_2$, highlighting a possible electronic structure change related to its magnetoresistance.

Findings

Hole density increases below ~160 K, indicating a Lifshitz transition.

Electron density decreases below 50 K, leading to electron-hole balance.

WTe$_2$ is unlikely to be perfectly electron-hole compensated.

Abstract

We systematically measured the Hall effect in the extremely large magnetoresistance semimetal WTe$_2$. By carefully fitting the Hall resistivity to a two-band model, the temperature dependencies of the carrier density and mobility for both electron- and hole-type carriers were determined. We observed a sudden increase of the hole density below $\sim$160~K, which is likely associated with the temperature-induced Lifshitz transition reported by a previous photoemission study. In addition, a more pronounced reduction in electron density occurs below 50~K, giving rise to comparable electron and hole densities at low temperature. Our observations indicate a possible electronic structure change below 50~K, which might be the direct driving force of the electron-hole ``compensation'' and the extremely large magnetoresistance as well. Numerical simulations imply that this material is unlikely to be a perfectly compensated system.