Topological Modulation of 2D Tellurium

Trigonal tellurium (Te) is a semiconductor with a bandgap of 0.3 eV. Recently, theoretical calculations predicted the existence of Weyl points near the band edges, so it is referred to as a Weyl semiconductor. Due to the narrow gap, we can study transport properties near Weyl points through gate modulation, which was not possible with Weyl semimetals. Near the conduction band edge only, we observed a strong Hall effect with no magnetic field. Under the time-reversal symmetry, various mechanisms have been invoked to generate transverse voltage, such as skew scattering, side-jump scattering, and current jetting. Our careful investigation details that the transverse Hall voltage scales in parabolic to the longitudinal input current I(w), i.e., V(2ω) ~ I²(ω). Intriguingly, V(DC) is linearly proportional to I²(ω) and display the same value with V(2ω). The results indicate that the Hall voltage of 2D Te has a topological origin of Berry curvature dipole (BCD). This effect arises due to the asymmetric distribution of Berry curvature in momentum space. At 4 K, 2D Te shows a much more significant on/off ratio, approximately 10⁴ in the transverse direction, than 10 in the longitudinal direction. The high on/off ratio implies that the nonlinear Hall voltage (NLHV) is sufficiently gate-modulable and opens a new possibility for topological electronics.