Quantifying the fragility of unprotected quadratic band crossing points

  title={Quantifying the fragility of unprotected quadratic band crossing points},
  author={S Hesselmann and Carsten Honerkamp and Stefan Wessel and Thomas C. Lang},
  journal={Physical Review B},
We examine a basic lattice model of interacting fermions that exhibits quadratic band crossing points (QBCPs) in the non-interacting limit. In particular, we consider spinless fermions on the honeycomb lattice with nearest neighbor hopping $t$ and third-nearest neighbor hopping $t''$, which exhibits fine-tuned QBCPs at the corners of the Brillouin zone for ${t'' = t/2}$. In this situation, the density of states remains finite at the Fermi level of the half-filled band and repulsive nearest… 

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