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.
@article{arxiv.2412.00461,
title = {Nonlinear optical response and spontaneous polarization in layer-stacked gallenene using second harmonic generation},
author = {Muhammad Yunusa and Andrew K. Schulz and Tim Parker and Felix Schneider and Kenan Elibol and Marius Predel and Jana Dzíbelová and Michel Rebmann and Taylan Gorkan and Peter A. van Aken and Alfred J. Meixner and Engin Durgun and Jani Kotakoski and Dai Zhang and Metin Sitti},
journal= {arXiv preprint arXiv:2412.00461},
year = {2025}
}