Predicting a graphene-like WB4 nanosheet with a double Dirac cone, an ultra-high Fermi velocity and significant gap opening by spin–orbit coupling

Abstract

The zero-band gap nature of graphene prevents it from performing as a semi-conductor in modern electronics. Although various graphene modification strategies have been developed to address this limitation, the very small band gap of these materials and the suppressed charge carrier mobility of the devices developed still significantly hinder graphene's applications. In this work, a two dimensional (2D) WB₄ monolayer, which exhibits a double Dirac cone, was conceived and assessed using density functional theory (DFT) methods, which would provide a sizable band gap while maintaining higher charge mobility with a Fermi velocity of 1.099 × 10⁶ m s⁻¹. Strong spin–orbit-coupling can generate an observable band gap of up to 0.27 eV that primarily originates from the d-orbit of the heavy metal atom W; therefore a 2D WB₄ nanosheet would be operable at room temperature (T = 300 K) and would be a promising candidate to fabricate nanoelectronics in the upcoming post-silicon era. The phonon-spectrum and ab initio molecular dynamics calculations further demonstrate the dynamic and thermal stability of such nanosheets, thus, suggesting a potentially synthesizable Dirac material.