A Z$_2$ index of Dirac operator with time reversal symmetry

T. Fukui, T. Fujiwara

Published 2009-05-22Version 1

With time reversal symmetry a Dirac operator has vanishing index and Chern number. We show that we can nevertheless define a nontrivial Z$_2$ index as well as a corresponding topological invariant given by gauge field, which implies that such a Dirac operator is topologically nontrivial.