Quasi-Topological Insulator and Trigonal Warping in Gated Bilayer Silicene

Abstract

Bilayer silicene has richer physical properties than bilayer graphene due to its buckled structure together with its trigonal symmetric structure. The buckled structure arises from a large ionic radius of silicon, and the trigonal symmetry from a particular way of hopping between two silicenes. It is a topologically trivial insulator since it carries a trivial ${\mathbb{Z}}_2$ topological charge. Nevertheless, its physical properties are more akin to those of a topological insulator than those of a band insulator. Indeed, a bilayer silicene nanoribbon has edge modes which are almost gapless and helical. We may call it a quasi-topological insulator. An important observation is that the band structure is controllable by applying the electric field to a bilayer silicene sheet. We investigate the energy spectrum of bilayer silicene under electric field. Just as monolayer silicene undergoes a phase transition from a topological insulator to a band insulator at a certain electric field, bilayer silicene makes a transition from a quasi-topological insulator to a band insulator beyond a certain critical field. Bilayer silicene is a metal while monolayer silicene is a semimetal at the critical field. Furthermore we find that there are several critical electric fields where the gap closes due to the trigonal warping effect in bilayer silicene.

8 pages, 11 figures, to be published in J. Phys. Soc. Jpn

References in corpus (5)

• Valley-Polarized Metals and Quantum Anomalous Hall Effect in Silicene
• The Helical Liquid and the Edge of Quantum Spin Hall Systems
• Spin-orbit coupling in a graphene bilayer and in graphite
• Band topology and quantum spin Hall effect in bilayer graphene
• Quantum Hall Effects in Silicene

Cited by in corpus (5)

• Spin-Valley Optical Selection Rule and Strong Circular Dichroism in Silicene
• Hexagonally Warped Dirac Cones and Topological Phase Transition in Silicene Superstructure
• Topological phase transition from trigonal warping in van der Waals multilayers
• Moiré-modulated band gap and van Hove singularities in twisted bilayer germanene
• Confinement in bilayer graphene via intra- and inter-layer interactions