Dirac points merging and wandering in a model Chern insulator

¹ CeFEMA, Instituto Superior Técnico, Universidade de Lisboa - Av. Rovisco Pais, 1049-001 Lisboa, Portugal
² Beijing Computational Science Research Center - Beijing 100084, China
³ Centro de Física das Universidades do Minho e Porto, Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto, Portugal

Received: 1 October 2018
Accepted: 13 December 2018

Abstract

We present a model for a Chern insulator on the square lattice with complex first- and second-neighbor hoppings and a sublattice potential which displays an unexpectedly rich physics. Similarly to the celebrated Haldane model, the proposed Chern insulator has two topologically non-trivial phases with Chern numbers ±1. As a distinctive feature of the present model, phase transitions are associated to Dirac points that can move, merge and split in momentum space, at odds with Haldane's Chern insulator where Dirac points are bound to the corners of the hexagonal Brillouin zone. Additionally, the obtained phase diagram reveals a peculiar phase transition line between two distinct topological phases, in contrast to the Haldane model where such transition is reduced to a point with zero sublattice potential. The model is amenable to be simulated in optical lattices, facilitating the study of phase transitions between two distinct topological phases and the experimental analysis of Dirac points merging and wandering.