Continuous preparation of a fractional Chern insulator

Speaker: 
Chris Laumann, Department of Physics, University of Washington
Event Date and Time: 
Thu, 2015-04-16 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Marcel Franz/Armin Rahmani
Intended Audience: 
Graduate

Fractional Chern insulators (FCI) are lattice-dominated realizations of conventional fractional quantum Hall states. For example, possible microscopic realizations of FCIs have been proposed in ultracold atomic gases and polar molecules. Unlike typical condensed matter systems, such quantum optical realizations are driven, non-equilibrium implementations. Thus, one cannot simply ‘cool’ into the FCI state by decreasing the temperature of a surrounding bath. One approach to this problem is provided by quasi-adiabatic preparation, wherein the correlated ground state is reached from a simple initial state by slowly tuning the Hamiltonian parameters. This requires understanding both the phases and transitions along the quasi-adiabatic path.

In this talk, I will describe our recent proposal for a microscopic realization of a v = 1/2 FCI in ultracold polar molecules. In the vicinity of the FCI phase, we numerically observe both superfluid and density wave insulators. These neighboring states are easily prepared but whether they enable the quasi-adiabatic preparation of the FCI depends on the nature of the phase transitions. I will present evidence of a direct, inversion-protected, continuous quantum phase transition between the superfluid and the FCI. In the process I will develop a detailed field theoretic description of the entire phase diagram in terms of the low energy vortices, explicitly taking into account the lattice symmetries and associated spontaneous symmetry breaking.

Joint work with: M. Barkeshli, N. Yao.

References:
        M. Barkeshli, N. Yao, CRL, arXiv:1407.7034
        N. Yao, CRL, et al. PRL 109, 266804 (2012), PRL 110, 185302 (2013).

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