Topological Phase Transition and Electrically Tunable Diamagnetism in Silicene

TL;DR

This paper investigates the topological phase transition in silicene induced by an external electric field, revealing the underlying pseudospin mechanism and proposing a method to determine the critical field via diamagnetism, with implications for future devices.

Contribution

It uncovers the pseudospin origin of the topological transition in silicene and introduces a diamagnetism-based approach to identify the critical electric field.

Findings

Diamagnetism in silicene exhibits a singular behavior at the phase transition.

The phase transition is driven by a pseudospin meron in momentum space.

Electric field can tune the diamagnetic response of silicene.

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 their 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. Our finding will be important for future electro-magnetic correlated devices.