Quantum-Geometric Origin of Out-of-plane Stacking Ferroelectricity

TL;DR

This paper reveals that out-of-plane stacking ferroelectricity in van der Waals materials originates from quantum geometric effects, specifically Berry phase phenomena modeled by an effective Su-Schrieffer-Heeger framework, providing a unified understanding beyond symmetry considerations.

Contribution

It introduces a quantum-geometric theory explaining out-of-plane stacking ferroelectricity, applicable to various bilayer materials and extending beyond traditional symmetry-based explanations.

Findings

Berry phase underpins stacking ferroelectric polarization.

The theory applies to transition-metal dichalcogenides and honeycomb bilayers.

Provides a quantitative framework for ferroelectricity in 2D materials.

Abstract

Stacking ferroelectricity (SFE) has been discovered in a wide range of van der Waals materials and holds promise for applications, including photovoltaics and high-density memory devices. We show that the microscopic origin of out-of-plane stacking ferroelectric polarization can be generally understood as a consequence of nontrivial Berry phase borne out of an effective Su-Schrieffer-Heeger model description with broken sublattice symmetry, thus elucidating the quantum-geometric origin of polarization in the extremely non-periodic bilayer limit. Our theory applies to known stacking ferroelectrics such as bilayer transition-metal dichalcogenides in 3R and T$_{\rm d}$ phases, as well as general AB-stacked honeycomb bilayers with staggered sublattice potential. Our explanatory and self-consistent framework based on the quantum-geometric perspective establishes quantitative understanding of out-of-plane SFE materials beyond symmetry principles.