Evolution of the topological properties of two-dimensional group IVA materials and device design

Abstract

Two-dimensional group IVA materials (graphene, silicene, germanene, stanene, and plumbene) are promising candidates for realization of the quantum spin Hall effect and for future device applications. We employ density functional theory, tight-binding models, and a Green's function method to systematically investigate their topological properties. From graphene to plumbene, the strength of spin-orbit coupling and the bulk gap increases with increasing atomic mass, and plumbene, as a normal insulator, is totally different from the other four materials, whose ground states are topological insulators. Through detailed analyses of orbital character weights and the evolution of low-energy states around the Γ point, we explain why plumbene is so different. Our quantum transport calculations also indicate that there exist electronic transport channels along edges within the bulk gap of topological insulators. By investigating the effects of external fields on the electronic structures of silicene, germanene, and stanene, we reveal a rich phase diagram and propose two filters with nearly 100% spin polarization. In addition, we present a theoretical design for a spin twister, based on curved two-dimensional topological insulators.

Magnetic properties of 3d transition metal (Sc–Ni) doped plumbene

“…15 According to theoretical calculations, plumbene is also a good candidate for realizing the quantum spin Hall effect at room temperature (RT). 19 Unexpected quantum spin Hall insulating properties were also reported for bilayer and decorated plumbene. 20,21 Over the past decades, there have been many studies regarding the fundamental science of dilute magnetic semiconductors (DMSs).…”

Constructive coupling effect of topological states and topological phase transitions in plumbene

“…The atomic Pb film with low-buckled configuration has been theoretically predicted to be as a topologically trivial insulator in Refs. [18][19][20] rather than QSH insulators found in other group IVA atomic films. Some researchers have been performed to tune the low-buckled plumbene from a topologically trivial insulator to a topologically nontrivial insulator, by such as chemical or electron doping [18,[20][21][22][23].…”

Quantum valley Hall effect in wide-gap semiconductor SiC monolayer

“…After successful preparation of graphene and discovery of its intriguing properties such as a massless Dirac fermion-like behavior of charge carriers at the Fermi level (E F ) and the quantum spin Hall effect under spin-orbit interaction [1][2][3] , a great deal of attention has been paid to the two-dimensional (2D) materials of honeycomb structure [4][5][6] . Graphene, silicene, germanene and stannene are monatomic 2D materials of group IV elements 4,7 . Unlike the completely flat graphene layer, other monatomic 2D group IV materials consist of a buckled layer.…”