Emergence of superconductivity in a doped single-valley quadratic band crossing system of spin-12 fermions

Kelly Ann Pawlak, James M. Murray, and Oskar Vafek
Phys. Rev. B 91, 134509 – Published 20 April 2015

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 d- and s-wave superconductivity are realized for short-ranged (Hubbard) and longer-ranged (forward scattering) interactions, respectively. In the sixfold-symmetric case, we find either s-wave superconductivity or no superconducting instability.

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  • Received 16 January 2015
  • Revised 28 March 2015

DOI:https://doi.org/10.1103/PhysRevB.91.134509

©2015 American Physical Society

Authors & Affiliations

Kelly Ann Pawlak1,2, James M. Murray2, and Oskar Vafek2

  • 1University of California, Santa Barbara, California 93106, USA
  • 2National High Magnetic Field Laboratory and Department of Physics, Florida State University, Tallahasse, Florida 32306, USA

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Issue

Vol. 91, Iss. 13 — 1 April 2015

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