Monday, June 10, 2013

1306.1816 (Hermann Schulz-Baldes et al.)

Invariants for J-unitaries on Real Krein spaces and the classification
of transfer operators

Hermann Schulz-Baldes, Carlos Villegas-Blas
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.
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