A discriminating string order parameter for topological phases of gapped   SU(N) spin chains
  One-dimensional gapped spin chains with symmetry PSU(N) = SU(N)/Z_N are known to possess N different topological phases. In this paper, we introduce a non-local string order parameter which characterizes each of these N phases unambiguously. Numerics confirm that our order parameter allows to extract a quantized topological invariant from a given non-degenerate gapped ground state wave function. Discontinuous jumps in the discrete topological order that arise when varying physical couplings in the Hamiltonian may be used to detect quantum phase transitions between different topological phases. 
Kasper Duivenvoorden, Thomas Quella
cond-mat.str-el cond-mat.stat-mech math-ph math.MP quant-ph