Engineering Weyl phases and nonlinear Hall effects in T${}_d$-MoTe${}_2$

Abstract

MoTe${}_2$ has recently attracted much attention due to the observation of pressure-induced superconductivity, exotic topological phase transitions, and nonlinear quantum effects. However, there has been debate on the intriguing structural phase transitions among various observed phases of MoTe${}_2$, and their connection to the underlying topological electronic properties. In this work, by means of density-functional theory (DFT+U) calculations, we investigate the structural phase transition between the polar T${}_d$ and nonpolar 1T${}^{\prime }$ phases of MoTe${}_2$ in reference to a hypothetical high-symmetry T${}_0$ phase that exhibits higher-order topological features. In the T${}_d$ phase we obtain a total of 12 Weyl points, which can be created/annihilated, dynamically manipulated, and switched by tuning a polar phonon mode. We also report the existence of a tunable nonlinear Hall effect in T${}_d$-MoTe${}_2$, and propose the use of this effect as a probe for the detection of polarity orientation in polar (semi)metals. By studying the role of dimensionality, we identify a configuration in which a nonlinear surface response current emerges. The potential technological applications of the tunable Weyl phase and the nonlinear Hall effect are discussed.