2009/08/31 by Meng Cheng, Kai Sun, Victor Galitski +1 · 2 citations
Physics and Astronomy · #Advanced Condensed Matter Physics #Physics of Superconductivity and Magnetism #Topological Materials and Phenomena #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.81.024504
published as Phys. Rev. B 81, 024504 (2010) · 6 pages, 2 figures, new references added
arxiv created 2009/11/25 · openalex publication_date 2010/01/08 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We show that a large class of two-dimensional spinless fermion models exhibit topological superconducting phases characterized by a nonzero Chern number. More specifically, we consider a generic one-band Hamiltonian of spinless fermions that is invariant under both time reversal, \mathbbT, and a group of rotations and reflections, \mathbbG, which is either the dihedral point-symmetry group of an underlying lattice, \mathbbG=Dn, or the orthogonal group of rotations in continuum, \mathbbG=O(2). Pairing symmetries are classified according to the irreducible representations of \mathbbT\ensuremath\bigotimes\mathbbG. We prove a theorem that for any two-dimensional representation of this group, a time-reversal symmetry-breaking paired state is energetically favorable. This implies that the ground state of any spinless fermion Hamiltonian in continuum or on a square lattice with a singly connected Fermi surface is always a topological superconductor in the presence of attraction in at least one channel. Motivated by this discovery, we examine phase diagrams of two specific lattice models with nearest-neighbor hopping and attraction on a square lattice and a triangular lattice. In accordance with the general theorem, the former model exhibits only a topological (p+ip)-wave state while the latter shows a doping-tuned quantum phase transition from such state to a nontopological but still exotic f-wave superconductor.