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HL: Fachverband Halbleiterphysik

HL 77: Low-dimensional systems: Topological order 1 (TT with HL)

HL 77.4: Vortrag

Donnerstag, 19. März 2015, 12:15–12:30, H 3010

Symmetry Protected Phases in Geometrically Frustrated 1D Antiferromagnets — •Alexander Nietner, Emil J. Bergholtz, and Jens Eisert — Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, 14195 Berlin, Germany

Geometrically frustrated (GF) systems admit an exotic phenomenology, such as spin liquid states, which lack any local order parameter. To reach a better understanding of such behaviour we realize the spin one Heisenberg antiferromagnetic Δ-chain (HAD) as a simple GF system in a numerically feasible regime. Inspired by a projected entangled pairs picture, we relate this system to a double layered ferromagnetically coupled s=1/2 HAD. We use the time dependent variational principle to compute the ground states of these systems and investigate their phase diagramme in the thermodynamic limit, analysing the entanglement spectra and the projective representations of the symmetry groups. Despite the simplicity of these systems, we find evidence of a topological phase transition for the latter one from the trivial phase in the weak ferromagnetic limit towards a symmetry protected non-trivial phase for a finite coupling strength. This is in good agreement with the fact that the corresponding s=1 system is found to be in the topological Haldane phase.