From a normal insulator to a topological insulator in plumbene

Abstract

Plumbene, similar to silicene, has a buckled honeycomb structure with a large band gap ($\sim 400$ meV). All previous studies have shown that it is a normal insulator. Here, we perform first-principles calculations and employ a sixteen-band tight-binding model with nearest-neighbor and next-nearest-neighbor hopping terms to investigate electronic structures and topological properties of the plumbene monolayer. We find that it can become a topological insulator with a large bulk gap ($\sim 200$ meV) through electron doping, and the nontrivial state is very robust with respect to external strain. Plumbene can be an ideal candidate for realizing the quantum spin Hall effect at room temperature. By investigating effects of external electric and magnetic fields on electronic structures and transport properties of plumbene, we present two rich phase diagrams with and without electron doping, and propose a theoretical design for a four-state spin-valley filter

Emerging Applications of Elemental 2D Materials

“…More recently, development in the elemental plumbene have shown an even larger energy gap of 400 meV, which is greater than that of the other group IV materials, namely graphene (10 −3 meV), silicene (8 meV), germanene (23 meV), and stanene (300 meV), approaching the energies needed for room temperature spintronics . Plumbene is predicted to become a topological insulator with a large bulk gap of 200 meV through electronic doping, which is robust to externally applied strain . More experimental work is needed to realize and test the feasibility and reliability of these spintronic devices, but the mounting theoretical evidence suggests potential technology revolutions in spintronics based on elemental 2D materials.…”

“…Stanene has been predicted to exhibit a large‐gap quantum spin gap of 0.3 eV, which could enable room temperature spintronics similar to those hypothesized in bismuthene . More recently, development in the elemental plumbene have shown an even larger energy gap of 400 meV, which is greater than that of the other group IV materials, namely graphene (10 −3 meV), silicene (8 meV), germanene (23 meV), and stanene (300 meV), approaching the energies needed for room temperature spintronics . Plumbene is predicted to become a topological insulator with a large bulk gap of 200 meV through electronic doping, which is robust to externally applied strain .…”

Topological phase transitions and quantum Hall effect in the graphene family

“…1). The spin-orbit couplings for silicene, germanene, stanene, and plumbene are λ SO ≈ 3.9,43,100,200 meV [8,[16][17][18], respectively. Terms originating from Rashba physics are ignored because of their comparatively small effect [16,17].…”

“…The two-dimensional (2D) staggered semiconductors [1][2][3] silicene [4], germanene [5], stanene [6,7], and plumbene [8] are monolayer materials made out of silicon, germanium, tin, and lead atoms, respectively. Together with graphene [9,10], they make up the group of monolayer honeycomb materials often referred to as the graphene family.…”

Graphene's Latest Cousin: Plumbene Epitaxial Growth on a “Nano WaterCube”

“…Typically, very recently, molecular dynamics simulations revealed that the mechanical properties of plumbene are several times greater than those of bulk lead . According to first‐principles calculations, free‐standing plumbene becomes a topological insulator with a large gap (≈200 meV) through electron doping, and the nontrivial state is very robust with respect to external strain . Moreover, first‐principles calculations with tight‐binding models and a Green's function method indicate that only plumbene in the group 14 offsprings of graphene is a topological insulator and an ideal candidate for realizing the quantum spin Hall effect at room temperature (RT) .…”