Experimental evidence of monolayer AlB${}_2$ with symmetry-protected Dirac cones

Abstract

Monolayer AlB${}_2$ is composed of two atomic layers: honeycomb borophene and triangular aluminum. In contrast with the bulk phase, monolayer AlB${}_2$ is predicted to be a superconductor with a high critical temperature. Here, we demonstrate that monolayer AlB${}_2$ can be synthesized on Al(111) via molecular beam epitaxy. Our theoretical calculations revealed that the monolayer AlB${}_2$ hosts several Dirac cones along the $\Gamma$--M and $\Gamma$--K directions; these Dirac cones are protected by crystal symmetries and are thus resistant to external perturbations. The extraordinary electronic structure of the monolayer AlB${}_2$ was confirmed via angle-resolved photoemission spectroscopy measurements. These results are likely to stimulate further research interest to explore the exotic properties arising from the interplay of Dirac fermions and superconductivity in two-dimensional materials.

arXiv comment5 pages, 4 figures

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• Growing borophene on metal substrates: a theoretical study of the role of oxygen on Al(111)
• A new alloy for Al-chalcogen system: AlSe surface alloy on Al (111)