# Electronic structure and tunability of 2D hexagonal boron arsenide

## TL;DR

This paper combines group theory and density functional theory to develop accurate models of the electronic bandstructure of 2D hexagonal boron arsenide, revealing its tunable electronic properties under strain and electric fields.

## Contribution

It introduces a new $k extit{ extperiodcentered}p$ Hamiltonian model for h-BAs, capturing effects of strain, electric, and magnetic fields with high accuracy.

## Key findings

- h-BAs is a direct bandgap material at the K point
- Electric field or biaxial strain can make the bandgap indirect
- High electric field or strain induces metallic behavior in h-BAs

## Abstract

Group theory and density functional theory methods are combined to obtain compact and accurate $k\cdot p$ Hamiltonians that describe the bandstructures around the $K$ and $\Gamma$ points for the 2D material hexagonal boron arsenide (h-BAs) predicted to be an important low-bandgap material for electric, thermoelectric, and piezoelectric properties that supplements the well-studied 2D material hexagonal boron nitride. Hexagonal boron arsenide is a direct bandgap material with band extrema at the $K$ point. The bandgap becomes indirect with a conduction-band minimum at the $\Gamma$ point subject to a strong electric field or biaxial strain. At even higher electric field strengths (approximately 0.75 V/$\r{A}$) or a large strain ($14$~\%) 2D hexagonal boron arsenide becomes metallic. Our $k\cdot p$ models include to leading orders the influence of strain, electric, and magnetic fields. Excellent qualitative and quantitative agreement between density functional theory and $k\cdot p$ predictions are demonstrated for different types of strain and electric fields.