Triple-well ferroelectricity and kagome-like Chern flat band in two-dimensional multiferroic CuVP$_2$Se$_6$

TL;DR

This paper predicts that monolayer CuVP$_2$Se$_6$ exhibits switchable ferroelectricity and hosts a kagome-like flat band with topological properties, making it a promising platform for tunable quantum phenomena.

Contribution

It introduces a new 2D multiferroic material with a tunable triple-well ferroelectric transition and a spin-polarized Chern flat band, analyzed through first-principles calculations.

Findings

Ferroelectric and paraelectric phases are close in energy and switchable by strain or electric field.

A kagome-like flat band appears near the Fermi level during the transition.

Magnetization direction influences the Chern number, enabling topological control.

Abstract

Two-dimensional multiferroics that host nontrivial topological bands offer a rich platform for correlated and tunable quantum phenomena, yet such materials remain rare. Here, using first-principles calculations, we reveal that monolayer CuVP$_2$Se$_6$ unites a tunable triple-well ferroelectric transition with a spin-polarized Chern flat band. The ferroelectric and paraelectric phases are close in energy and can be reversibly switched by moderate strain or an electric field. During the transition, a kagome-like flat band emerges near the Fermi level, which we describe via a minimal three-orbital tight-binding model on a triangular lattice. Furthermore, the system exhibits sizable magnetic anisotropy and a magnetization-dependent Chern insulating state: the Chern number is $C = \pm 1$ for out-of-plane magnetization but becomes trivial when the moments rotate in-plane. These findings establish CuVP$_2$Se$_6$ as a promising candidate for exploring electrically tunable flat-band correlations and topological magnetism in a multiferroic monolayer.