Observation of a Dirac state in borophene hetero-bilayers by Cr intercalation

Abstract

By intercalating Cr atoms into borophene hetero-bilayers (BHBs), three kinds of Cr@BHBs, namely, Cr@BHB_(α1,β), Cr@BHB_(α1,β1) and Cr@BHB_(β,β1) are constructed and intriguing electronic and magnetic properties are predicted by density functional theory calculations. Interestingly, a Dirac cone is found in Cr@BHB_(α1,β), which is well conserved even under 8% tensile strain along uniaxial x and biaxial xy directions, and up to 4% tensile strain along the y direction. On the contrary, the Dirac cone disappears when exerting biaxial or uniaxial compressive strains, and Cr@BHB_(α1,β) is transformed into a ferromagnetic half metal or metal eventually. In addition, the Cr@BHB_(α1,β1) and Cr@BHB_(β,β1) isomers are found to be an antiferromagnetic semiconductor and ferromagnetic half metal, respectively, and their electronic and magnetic properties are sensitive to the external strains. Our study proposes a pathway for designing borophene based materials with intriguing properties, which may have potential applications in electronics and spintronics.