Nonlinear optical response and spontaneous polarization in layer-stacked gallenene using second harmonic generation

TL;DR

This study investigates the nonlinear optical properties and stacking behavior of gallenene, a 2D material, revealing its potential for device applications through second harmonic generation microscopy.

Contribution

It provides the first evidence of AB stacking in liquid gallium and characterizes the nonlinear optical response of confined gallenene using SHG microscopy.

Findings

Observed AB stacking of 2D gallenene in liquid gallium.

Detected periodic SHG intensity shifts with rotation.

Noted temperature-dependent dampening of SHG signal.

Abstract

Gallenene is a promising low-dimensional material with a structure down to the thickness of a single atom, similar to graphene. However, van der Waals stacking of two-dimensional (2D) gallenene under confinement remain poorly understood. In this study, we present evidence of the formation of parallel-stacked hexagonal gallenene (a100) structures in liquid gallium. The present study demonstrates the AB stacking of 2D gallenene a100 crystals in liquid gallium sandwiched between two graphene layers, as observed through transmission electron microscopy. A nonlinear optical response of the confined hexagonal gallenene was investigated through second harmonic generation (SHG) microscopy. The SHG signal exhibits periodic peak intensity shifts upon angular rotation up to 90 degrees and intensity dampening at elevated temperatures. These findings offer insights on device applications of 2D gallenene.