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

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.

10 pages, 5 figures