Evidence of the ferroelectric polarization in charge transport through WTe$_2$ Weyl semimetal surface

TL;DR

This study demonstrates ferroelectric polarization in WTe$_2$ Weyl semimetal surface through non-linear transport behavior and hysteresis, revealing room-temperature coexistence of Weyl conductivity and ferroelectricity.

Contribution

It provides the first direct evidence of ferroelectric polarization affecting charge transport in WTe$_2$ at room temperature.

Findings

Observation of slow relaxation in differential resistance.

Identification of ferroelectric hysteresis in transport measurements.

Confirmation of ferroelectric polarization via gate voltage dependence.

Abstract

We investigate electron transport along the surface of WTe$_2$ three-dimensional single crystals, which are characterized by coexistence of Weyl semimetal conductivity and ferroelectricity at room temperature. We find that non-linear behavior of $dV/dI(I)$ WTe$_2$ differential resistance is accompanied by slow relaxation process, which appears as the $dV/dI(I)$ dependence on the sign of the current change. This observation is confirmed by direct investigation of time-dependent relaxation curves. While strongly non-linear differential resistance should be expected for the zero-gap WTe$_2$, the slow relaxation in transport is very unusual for well-conducting semimetals at room temperature. We establish, that non-monotonous dependence of the amplitude of the effect on driving current $\Delta dV/dI(I)$ well corresponds to the known Sawyer-Tower's ferroelectric hysteresis loop. This conclusion is also confirmed by gate voltage dependencies, so our results can be understood as a direct demonstration of WTe$_2$ ferroelectric polarization in charge transport experiment.