Negative Compressibility in Graphene-terminated Black Phosphorus Heterostructures

TL;DR

This paper reports the observation of negative compressibility in black phosphorus heterostructures, which enhances gate capacitance due to many-body Coulomb effects, enabled by ultraclean interfaces.

Contribution

It demonstrates negative compressibility in black phosphorus heterostructures and explains it through Coulomb correlation and Debye screening, a novel observation in this material.

Findings

Capacitance enhancement observed in black phosphorus heterostructures

Negative compressibility occurs at low hole carrier concentrations

Coulomb correlation explains the negative compressibility

Abstract

Negative compressibility generated by many-body effects in 2D electronic systems can enhance gate capacitance. We observe capacitance enhancement in a newly emerged 2D layered material, atomically thin black phosphorus (BP). The encapsulation of BP by hexagonal boron nitride sheets with few-layer graphene as a terminal ensures ultraclean heterostructure interfaces, allowing us to observe negative compressibility at low hole carrier concentrations. We explained the negative compressibility based on the Coulomb correlation among in-plane charges and their image charges in a gate electrode in the framework of Debye screening.