Intralayer Negative Poisson's Ratio in Two-Dimensional Black Arsenic by Strain Engineering

TL;DR

This study demonstrates the intrinsic intralayer negative Poisson's ratio in natural two-dimensional black arsenic through strain engineering, supported by Raman spectroscopy and theoretical calculations, revealing unique anisotropic mechanical properties.

Contribution

First experimental observation of negative Poisson's ratio in a natural 2D material, black arsenic, using strain engineering and Raman spectroscopy.

Findings

Black arsenic exhibits intralayer negative Poisson's ratio.

Anisotropic Raman response correlates with strain and mechanical properties.

Van der Waals interactions influence strain-dependent behavior.

Abstract

Negative Poisson's ratio as the anomalous characteristic generally exists in artificial architectures, such as re-entrant and honeycomb structures. The structures with negative Poisson's ratio have attracted intensive attention due to their unique auxetic effect and many promising applications in shear resistant and energy absorption fields. However, experimental observation of negative Poisson's ratio in natural materials barely happened, although various two-dimensional layered materials are predicted in theory. Herein, we report the anisotropic Raman response and the intrinsic intralayer negative Poisson's ratio of two-dimensional natural black arsenic (b-As) via strain engineering strategy. The results were evident by the detailed Raman spectrum of b-As under uniaxial strain together with density functional theory calculations. It is found that b-As was softer along the armchair than zigzag direction. The anisotropic mechanical features and van der Waals interactions play essential roles in strain-dependent Raman shifts and negative Poisson's ratio in the natural b-As along zigzag direction. This work may shed a light on the mechanical properties and potential applications of two-dimensional puckered materials.