Computational realization of Dirac nodal point and Dirac nodal loop fermions in novel β-graphyne analogues

Abstract

In this study, we have predicted four novel analogues of β-graphyne using density functional theory based first-principles calculations. The geometrical parameters, thermodynamic stabilities, energetic favorability and electronic properties of these four novel two-dimensional (2D) materials have been investigated to assess the structural stability and experimental feasibility. Phonon band dispersion analysis and molecular dynamics simulation studies authenticate the dynamic and thermal stability of all these 2D materials. Electronic structure calculations show that two 2D materials are semimetallic while the other two are semiconducting in nature. The semimetallic sheets are furnished with a Dirac nodal loop (DNL), multiple Dirac points, massless Dirac fermions and ultra-high Fermi velocities (0.47–0.99 × 10⁶ m s⁻¹). Interestingly, the semiconducting sheets also have low effective mass fermions. Further, the electronic structures of the nanoribbons and nanotubes of the semimetallic sheets have also been examined.