Spontaneous curvature in two-dimensional van der Waals heterostructures

TL;DR

This study predicts that 2D van der Waals heterostructures naturally develop out-of-plane curvature at interfaces, affecting their atomic and electronic structures, with implications for device applications.

Contribution

The paper introduces the concept of spontaneous curvature in 2D heterostructures and demonstrates it through deep-learning-assisted molecular dynamics simulations.

Findings

Significant out-of-plane displacements up to 3.8 Å observed in graphene/BN bilayers.

Stable hexagonal moire patterns form due to curvature.

Curvature influences mechanical properties and atomic arrangements.

Abstract

Two-dimensional (2D) van der Waals (vdW) heterostructures consist of different 2D crystals with diverse properties, constituting the cornerstone of the new generation of 2D electronic devices. Yet interfaces in heterostructures inevitably break bulk symmetry and structural continuity, resulting in delicate atomic rearrangements and novel electronic structures. In this paper, we predict that 2D interfaces undergo spontaneous curvature, which means when two flat 2D layers approach each other, they inevitably experience out-of-plane curvature. Based on deep-learning-assisted large-scale molecular dynamics simulations, we observed significant out-of-plane displacements up to 3.8 angstrom in graphene/BN bilayers induced by curvature, producing a stable hexagonal moire pattern, which agrees well with experimentally observations. Additionally, the out-of-plane flexibility of 2D crystals enables the propagation of curvature throughout the system, thereby influencing the mechanical properties of the heterostructure. These findings offer fundamental insights into the atomic structure in 2D vdW heterostructures and pave the way for their applications in devices.