Emergence of topological Mott insulators in proximity of quadratic band touching points

TL;DR

This paper demonstrates through mean-field theory that quadratic band touching points in a checkerboard lattice can lead to topological Mott insulators even away from half-filling, broadening the potential for experimental realization.

Contribution

It shows that interactions induce topological insulating phases near quadratic band touching points beyond half-filling, expanding the understanding of correlated topological phases.

Findings

Instability to topological phases away from half-filling

Interaction parameters can be tuned to achieve topological phases

Topological phases extend to regions with positive V and μ

Abstract

Recently, the field of strongly correlated electrons has begun an intense search for a correlation induced topological insulating phase. An example is the quadratic band touching point which arises in a checkerboard lattice at half-filling, and in the presence of interactions gives rise to topological Mott insulators. In this work, we perform a mean-field theory computation to show that such a system shows instability to topological insulating phases even away from half-filling (chemical potential $\mu = 0 $). The interaction parameters consist of on-site repulsion ($ U $), nearest-neighbour repulsion ($ V $), and a next-nearest-neighbour correlated hopping ($ t_\text{c} $). The $t_\text{c}$ interaction originates from strong Coulomb repulsion. By tuning the values of these parameters, we obtain a desired topological phase that spans the area around $(V = 0 , \mu = 0)$, extending to regions with $(V>0,\mu=0)$ and $(V>0,\mu>0)$. This extends the realm of current experimental efforts to find these topological phases.