Electric control of the topological phase transition in ferrovalley systems through valley-dependent electric dipoles

Abstract

<p>Two-dimensional ferrovalley systems are considered as an ideal platform to explore valley-related topological properties. To date, valley-related topological phase transitions have been mostly achieved through magnetic or optical means based on time-reversal symmetry breaking, yet electric approaches are highly desirable for topological device applications. Here, we propose that electric gating can drive valley-selective topological phase transitions assisted by valley-dependent out-of-plane electric dipole moments in ferrovalley systems without some specific symmetries. Specifically, an out-of-plane electric field induces valley-contrasted Stark shifts by coupling to the valley-dependent dipole moments, leading to field-strength-driven energy gap closing and reopening in a selected valley depending on the field's direction. Based on first-principles calculations, we present asymmetrically halogenated monolayer 1T-MoSe2 as a candidate material to validate our proposal. Notably, topological phase transition from an intrinsic quantum anomalous Hall state to a quantum valley Hall state is achieved by electric gating. Our work paves the way for the electric control of topological phase transitions in ferrovalley systems.</p>