Electronic structure of a borophene layer in rare-earth aluminum/chromium boride and its hydrogenated derivative borophane
Masahito Niibe, Mathis Cameau, Nguyen Thanh Cuong, Omeji Ilemona Sunday, Xiaoni Zhang, Yuki Tsujikawa, Susumu Okada, Kunio Yubuta, Takahiro Kondo, Iwao Matsuda
Abstract
We studied electronic states of borophene in a crystal of rare-earth aluminum/chromium boride and the hydrogenated sheet, borophane, successfully prepared by ion exchange and liquid exfoliation of the crystal. The layer has a boron network with five-membered and seven-membered rings. Electronic structures of all the boron-derived layers are found to be gapless by soft x-ray absorption and emission spectroscopy measurements at the B K-shell absorption edge and density functional theory calculations. The present results support the existence of a Dirac nodal loop at the Fermi level in the borophane layer with five- and seven-membered rings, predicted recently by topological calculations.