Abstract
We study the quantum phases driven by interaction in a semimetal with a quadratic band touching at the Fermi level. By combining the density matrix renormalization group (DMRG), analytical power expanded Gibbs potential method, and the weak coupling renormalization group, we study a spinless fermion system on a checkerboard lattice at half-filling, which has a quadratic band touching in the absence of interaction. In the presence of strong nearest-neighbor () and next-nearest-neighbor () interactions, we identify a site nematic insulator phase, a stripe insulator phase, and a phase separation region, in agreement with the phase diagram obtained analytically in the strong coupling limit (i.e., in the absence of fermion hopping). In the intermediate interaction regime we establish a quantum anomalous Hall phase in the DMRG as evidenced by the spontaneous time-reversal symmetry breaking and the appearance of a quantized Chern number . For weak interaction we utilize the power expanded Gibbs potential method that treats and on equal footing, as well as the weak coupling renormalization group. Our analytical results reveal that not only the repulsive interaction, but also the interaction (both repulsive and attractive), can drive the quantum anomalous Hall phase. We also determine the phase boundary in the plane that separates the semimetal from the quantum anomalous Hall state. Finally, we show that the nematic semimetal, which was proposed for at weak coupling in a previous study, is absent, and the quantum anomalous Hall state is the only weak coupling instability of the spinless quadratic band touching semimetal.
12 More- Received 19 May 2018
DOI:https://doi.org/10.1103/PhysRevB.98.125144
©2018 American Physical Society