CMSP Journal Club

Strange correlations in Symmetry Protected Topological phases

by Prof. Pinaki Sengupta (NTU Singapore)

Thursday, June 7, 2018 from to (Asia/Kolkata)
at A304
Due to the lack of long range entanglement and absence of any local order, identifying a Symmetry Protected Topological phase in an arbitrary Hamiltonian with competing interactions remains a challenge. Recently, a “strange correlator” has been proposed as a direct probe for the topological character of interacting Symmetry Protected Topological (SPT) phases. Using projective quantum Monte Carlo, we are able to directly access the strange correlator in a variety of phases, as well as to examine its critical behavior at the quantum phase transition between trivial and non-trivial symmetry protected topological phases. We demonstrate the underlying principles of the strange correlator within the context of the S=1 Heisenberg model with an easy-plane single ion anisotropy. We show that the evolution of the ground state from the topologically non-trivial Haldane phase to the topologically trivial quantum paramagnetic state with increasing single ion anisotropy can be accurately tracked by the strange correlator. Next we go on to verify the topological nature of two-leg and three-leg spin-1 Heisenberg antiferromagnetic ladders. This demonstrates the power of the strange correlator in distinguishing between trivial and non-trivial symmetry protected topological phases.