Nonlinear Hall effect in epitaxial WTe₂ thin film

In exfoliated few-layer T_d-WTe₂, it has previously been shown that an applied longitudinal electrical current can generate a nonlinear anomalous Hall effect in time-reversal symmetric conditions. This nonlinear Hall effect is a manifestation of the Berry dipole that originates from the opposite Berry curvatures of the two Weyl nodes in T_d-WTe₂, which is known as a Weyl semimetal. In this talk, we present our studies of the nonlinear Hall effect in epitaxial few-layer Td-WTe2 samples grown by molecular beam epitaxy. By measuring the 2nd harmonic response of the transverse voltage in the presence of an applied longitudinal electrical current, we have observed a voltage signal that scales quadratically with respect to the current. The signal exists at zero magnetic field and is independent of the frequency used in the measurement – mimicking the nonlinear Hall effect. We discuss the relationship of this signal with respect to the lattice symmetry in WTe2, which is calibrated using in-situ reflection high-energy electron diffraction during the growth. We will further discuss the temperature and angle dependence of the nonlinear Hall signal in epitaxial WTe2 samples and correlate it to magneto-transport studies.