%0 Journal Article
%T Invariants for J-unitaries on Real Krein spaces and the classification of transfer operators
%A Hermann Schulz-Baldes
%A Carlos Villegas-Blas
%J Physics
%D 2013
%I arXiv
%X Essentially S^1-gapped J-unitaries on a Krein space (K,J) conserving, moreover, a Real structure, are shown to possess Z or Z_2-valued homotopy invariants which can be expressed in terms of Krein inertia of the eigenvalues on the unit circle and are rooted in a detailed analysis of their collisions. When applied to the transfer operators associated with periodic two-dimensional tight-binding Hamiltonians, these new invariants determine the existence and nature of the surface modes (Majorana or conventional fermions, chirality) and allow to distinguish different phases of various topological insulators.
%U http://arxiv.org/abs/1306.1816v1