Phase transition of layer-stacked borophene under pressure
Xiao‐Ji Weng, Quansheng Wu, Xi Shao, Oleg V. Yazyev, Xin‐Ling He, Xiao Dong, Hui‐Tian Wang, Xiang‐Feng Zhou, Yongjun Tian
Abstract
The 8-$Pmmn$ borophene, a boron analog of graphene, hosts tilted and anisotropic massless Dirac fermion quasiparticles owing to the presence of a distorted graphenelike sublattice. First-principles calculations show that stacked 8-$Pmmn$ borophene is transformed into fused three-dimensional borophene under pressure, being accompanied by partial bond breaking and bond reformation. Strikingly, fused 8-$Pmmn$ borophene inherits the Dirac band dispersion resulting in an unusual semimetal-semimetal transition. A simple tight-binding model derived from graphene qualitatively reveals the underlying physics due to the maximum preservation of the graphenelike substructure after the phase transition, which contrasts greatly to the transformation of graphite into diamond associated with the semimetal-insulator transition.