Experimental evidence of monolayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>AlB</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> with symmetry-protected Dirac cones
Daiyu Geng, Kejun Yu, Shaosheng Yue, Jin Cao, Wenbin Li, Da‐Shuai Ma, Chaoxi Cui, Masashi Arita, Shiv Kumar, Eike F. Schwier, K. Shimada, Peng Cheng, Lan Chen, Kehui Wu, Yugui Yao, Baojie Feng
Abstract
Monolayer ${\mathrm{AlB}}_{2}$ is composed of two atomic layers: honeycomb borophene and triangular aluminum. In contrast with the bulk phase, monolayer ${\mathrm{AlB}}_{2}$ is predicted to be a superconductor with a high critical temperature. Here, we demonstrate that monolayer ${\mathrm{AlB}}_{2}$ can be synthesized on Al(111) via molecular beam epitaxy. Our theoretical calculations revealed that the monolayer ${\mathrm{AlB}}_{2}$ hosts several Dirac cones along the $\mathrm{\ensuremath{\Gamma}}\text{\ensuremath{-}}M$ and $\mathrm{\ensuremath{\Gamma}}\text{\ensuremath{-}}K$ directions; these Dirac cones are protected by crystal symmetries and are thus resistant to external perturbations. The extraordinary electronic structure of the monolayer ${\mathrm{AlB}}_{2}$ 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.