Tuning Band Gaps in Twisted Bilayer Borophene

Abstract

Two-dimensional (2D) materials have captured considerable attention owing to their different properties compared to those of three-dimensional (3D) structures. The participation of rotation angles allows 2D bilayer materials to show more diverse physical properties. Here, we investigated the structural and electronic properties of bilayer borophene with four different rotation angles using first-principles calculations based on the density functional theory method. We found that the cohesive energy shows the same trend as the interlayer spacing, where the system with 83.1° is the most stable and its partial charge density shows the formation of apparent interlayer π-bonds. Meanwhile, the rotation angles alter the energy band structures and reduce the band gap sizes. It is worth noting that when 83.1°, a Dirac-like cone exists in Γ-Y. Finally, 31.4 and 83.1° bilayer borophene with initial band gaps exhibit the same band gap change behavior under external electric fields. These results extend the understanding of the interlayer interactions of twisted bilayer borophene with van der Waals interactions and provide a new and effective approach to precisely tune the band structure in bilayer materials.