Eur. Phys. J. B (2012) 85: 363
https://doi.org/10.1140/epjb/e2012-30577-0

Regular Article

Topological phase transition and electrically tunable diamagnetism in silicene

Department of Applied Physics, University of Tokyo, Hongo 7-3-1, 113-8656 Tokyo, Japan

^a e-mail: ezawa@ap.t.u-tokyo.ac.jp

Received: 30 May 2012
Received in final form: 11 July 2012
Published online: 5 November 2012

Abstract

Silicene is a monolayer of silicon atoms forming a honeycomb lattice. The lattice is actually made of two sublattices with a tiny separation. Silicene is a topological insulator, which is characterized by a full insulating gap in the bulk and helical gapless edges. It undergoes a phase transition from a topological insulator to a band insulator by applying external electric field. Analyzing the spin Chern number based on the effective Dirac theory, we find the origin to be a pseudospin meron in the momentum space. The peudospin degree of freedom arises from the two-sublattice structure. Our analysis makes clear the mechanism how a phase transition occurs from a topological insulator to a band insulator under increasing electric field. We propose a method to determine the critical electric field with the aid of diamagnetism of silicene. Diamagnetism is tunable by the external electric field, and exhibits a singular behaviour at the critical electric field. Our result is important also from the viewpoint of cross correlation between electric field and magnetism. Furthermore, nano-electromechanic devices transforming electric force to mechanical force may be feasible. Our finding will be important for future electro-magnetic correlated devices.