Layer-dependent pressure effect on electronic structures of 2D black phosphorus

TL;DR

This study systematically investigates how pressure affects the electronic structures of few-layer black phosphorus, revealing layer-dependent shifts in optical transitions and contrasting behaviors with bulk BP, using spectroscopy and modeling.

Contribution

It introduces a comprehensive analysis of pressure effects on 2D black phosphorus's electronic properties, highlighting layer-dependent behaviors and employing a combined experimental and theoretical approach.

Findings

Pressure-induced optical transition shifts are layer-dependent.

2L BP's bandgap increases with pressure beyond 2 GPa.

The pressure effects are explained by a tight-binding model with Morse potential.

Abstract

Through infrared spectroscopy, we systematically study the pressure effect on electronic structures of few-layer black phosphorus (BP) with layer number ranging from 2 to 13. We reveal that the pressure-induced shift of optical transitions exhibits strong layer-dependence. In sharp contrast to the bulk counterpart which undergoes a semiconductor to semimetal transition under ~1.8 GPa, the bandgap of 2 L increases with increasing pressure until beyond 2 GPa. Meanwhile, for a sample with a given layer number, the pressure-induced shift also differs for transitions with different indices. Through the tight-binding model in conjunction with a Morse potential for the interlayer coupling, this layer- and transition-index-dependent pressure effect can be fully accounted. Our study paves a way for versatile van der Waals engineering of two-dimensional BP.