A (single flavor) quadratic band crossing in two dimensions is known to have a generic instability towards a quantum anomalous Hall (QAH) ground state for infinitesimal repulsive interactions. Here we introduce a generalization of a quadratic band crossing which is protected only by rotational symmetry. By focusing on the representative case of a parabolic and flat band touching, which also allows for a straightforward lattice realization, the interaction induced nematic phase becomes the dominant instability in certain parts of the phase diagram already at weak coupling, by competing successfully with the QAH insulator. The full phase diagram of the model, together with its topological properties, is mapped out using a perturbative renormalization-group, strong-coupling analysis, the mean-field theory. Interestingly, the Berry flux varies continuously in the single flavor limit with various control parameters.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Jul 24 2014|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics