Abstract
For two-dimensional single-valley quadratic band crossing systems with weak repulsive electron-electron interactions, we show that upon introducing a chemical potential, particle-hole order is suppressed and superconductivity becomes the leading instability. In contrast to the two-valley case realized in bilayer graphene, the single-valley quadratic band touching is protected by crystal symmetries, and the different symmetries and number of fermion flavors can lead to distinct phase instabilities. Our results are obtained using a weak-coupling Wilsonian renormalization group procedure on a low-energy effective Hamiltonian relevant for describing electrons on checkerboard or kagome lattices. In fourfold-symmetric systems, we find that - and -wave superconductivity are realized for short-ranged (Hubbard) and longer-ranged (forward scattering) interactions, respectively. In the sixfold-symmetric case, we find either -wave superconductivity or no superconducting instability.
2 More- Received 16 January 2015
- Revised 28 March 2015
DOI:https://doi.org/10.1103/PhysRevB.91.134509
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