Topological invariants of time reversal invariant superconductors
arXiv:cond-mat/0608064
Abstract
The topological invariants of gapped time reversal invariant lattice superconductors are studied by mapping the superconducting mean field Hamiltonian to a Bloch Hamiltonian. There is a single $Z_2 $ invariant in two dimensions and four such invariants in three dimensions. We briefly discuss the properties of states with non-trivial topological invariants.
brief note on topological invariants for superconductors