Hidden topological order in 1D Bose insulators

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• Ehud Altman (Weizmann Institute)
• Monday 28 April 2008, 15:30-16:30
• HEP Seminar Room (980) Rutherford Building, Cavendish Laboratory.

If you have a question about this talk, please contact pjh65.

Ground states of integer spin chains are known since the late 80’s to sustain highly non local order described by infinite string operators of the spins. Such states defy the usual Landau theory description and can be considered simple prototypes of topological order. Recently we established the existence of an analogous phase of spinless bosons, which exhibits similar string order in terms of the boson density. Moreover, the Bose system can be tuned across quantum phase transitions between the exotic phase, which we term Haldane insulator, and the conventional Mott and density wave states. The response of the system to external perturbations near these phase transitions is revealing of the unusual character of the string order. In particular I will show how a perturbation, seemingly unrelated by symmetry to either phase, eliminates the critical point between the Mott and Haldane phases and allows adiabatic connection between them. Finally I will establish the existence of a distinct collective mode that can serve to identify the new phase in Bragg spectroscopy experiments.

This talk is part of the AMOP list series.

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