Nonvolatile Ferroelectric Manipulation of Topological States in Two-Dimensional Multiferroic van der Waals Heterostructures.

Multiferroic materials, including tunable ferrovalley characteristics and band topology, enabled by ferroelectric control at the nanoscale, possess significant potential for technology advances in next-generation magnetoelectric and spintronic applications. However, the realization of this fascinating multifunctionality in nanoscale systems with perpendicular magnetic anisotropy remains unexplored. Here, we propose a class of van der Waals multiferroic heterostructures comprising ferromagnetic, ferrovalley, and ferroelectric layers that exhibit switchable topological states in response to ferroelectric polarization. Taking the InSe/RuClBr/CrI heterostructure as an example, our first-principles calculations reveal its perpendicular magnetic anisotropy and band topology transition under different ferroelectric polarizations. When the ferroelectric polarization is downward, the heterostructure exhibits a type-III band alignment with metallic properties. Remarkably, when the polarization direction is reversed upward, it demonstrates a type-I band alignment accompanied by the emergence of a quantum anomalous Hall effect. Consequently, by manipulating the ferroelectric polarization direction, the multiferroic heterostructure can switch between normal metal behavior and a nonvolatile topological insulator. This study not only proposes a viable approach for tailoring topological states through multiferroic heterostructures but also demonstrates its potential significance in advancing multifunctional spintronic applications in ferroelectronics, valleytronics, and topology.