Electronic properties of 8-Pmmn borophene

TL;DR

This study uses first-principles calculations to explore the unique electronic properties of monolayer 8-Pmmn borophene, revealing its ionic features, Dirac cones, and potential to become a semiconductor under shear stress.

Contribution

It is the first to identify the ionic sublattice features and tunable electronic properties of 8-Pmmn borophene through detailed computational analysis.

Findings

Presence of Dirac cones formed by p_z orbitals of one sublattice

Potential to convert metallic borophene into an indirect band gap semiconductor with shear stress

Stability of strained structures confirmed by phonon analysis

Abstract

First-principles calculations on monolayer 8-{\it Pmmn} borophene are reported to reveal unprecedented electronic properties in a two-dimensional material. Based on a Born effective charge analysis, 8-{\it Pmmn} borophene is the first single-element based monolayered material exhibiting two sublattices with substantial ionic features. The observed Dirac cones are actually formed by the p$_z$ orbitals of one of the inequivalent sublattices composed of uniquely four atoms, yielding an underlying hexagonal network topologically equivalent to distorted graphene. A significant physical outcome of this effect includes the possibility of converting metallic 8-{\it Pmmn} borophene into an indirect band gap semiconductor by means of external shear stress. The stability of the strained structures are supported by a phonon frequency analysis. The Dirac cones are sensitive to the formation of vacancies only in the inequivalent sublattice electronically active at the Fermi level.