Deformation potential driven photostriction in layered ferroelectrics

TL;DR

This paper reveals that in multilayer SnS, deformation potential effects dominate over piezoelectric screening, leading to a unique polar-axis expansion upon photoexcitation, advancing understanding of photostriction in layered ferroelectrics.

Contribution

It demonstrates that deformation potential drives photostriction in multilayer SnS, contrasting with previous predictions of piezoelectric screening effects in similar materials.

Findings

Deformation potential causes polar-axis expansion in multilayer SnS.

Intrinsic photostrictive strain is distinguished from extrinsic artifacts.

Stacking-engineered SnS enables ultrafast optomechanical transduction.

Abstract

The coupling between electronic excitations and lattice deformation in van der Waals ferroelectrics is governed by a competition between the electron deformation potential and the inverse piezoelectric effect. While theory predicts that piezoelectric screening should drive a polar-axis contraction in monolayer group-IV monochalcogenides, we demonstrate that in multilayer SnS, the deformation potential provides the dominant contribution, driving a polar-axis expansion even within ferroelectric domains. By correlating polarization-resolved second-harmonic generation microscopy with ultrafast reflectance spectroscopy and first-principles calculations, we resolve the anisotropic lattice response and disentangle intrinsic photostrictive strain from extrinsic thin-film interference artifacts. These results establish a microscopic hierarchy of photostrictive mechanisms and position stacking-engineered SnS as a platform for ultrafast optomechanical transduction.