Dirac Nodal Lines and Tilted Semi-Dirac Cones Coexisting in a Striped Boron Sheet

TL;DR

This paper predicts a new boron monolayer, hr-sB, exhibiting coexisting Dirac nodal lines and tilted semi-Dirac cones, with potential applications in superconductivity and electronic devices.

Contribution

The study introduces a novel boron monolayer with coexisting Dirac fermions and detailed DFT analysis of its stability and electronic properties.

Findings

Identified hr-sB with Dirac nodal lines and semi-Dirac cones.

Predicted high stability comparable to experimental boron sheets.

Suggested potential for superconductivity in hr-sB.

Abstract

The enchanting Dirac fermions in graphene stimulated us to seek for other two-dimensional (2D) Dirac materials, and boron monolayers may be a good candidate. So far, a number of monolayer boron sheets have been theoretically predicted, and three have been experimentally prepared. However, none of them possesses Dirac electrons. Herein, by means of density functional theory (DFT) computations, we identified a new boron monolayer, namely hr-sB, with two types of Dirac fermions coexisting in the sheet: one type is related to Dirac nodal lines traversing Brillouin zone (BZ) with velocities approaching 106 m/s, the other is related to tilted semi-Dirac cones with strong anisotropy. This newly predicted boron monolayer consists of hexagon and rhombus stripes. With an exceptional stability comparable to the experimentally achieved boron sheets, it is rather optimistic to grow hr-sB on some suitable substrates such as the Ag (111) surface. The unique electronic properties induced by special bond characteristics also imply that this boron monolayer may be a good superconductor.