Wednesday, July 10, 2013

1307.2256 (Matthew S. Foster et al.)

Far from equilibrium topological p-wave superfluids    [PDF]

Matthew S. Foster, Victor Gurarie, Maxim Dzero, Emil A. Yuzbashyan
Recent years have witnessed an explosion in the study of topological superconductors, which carry energy currents along their boundaries in a topologically protected way, while these currents are suppressed in the bulk. Topological superconductors can host Majorana fermions, actively sought-after fractional particles. The simplest superconductor of this kind is a two-dimensional p-wave fermionic superfluid, with order parameter symmetry of the px+ipy type. It was expected that systems of ultracold atoms close to a p-wave Feshbach resonance would form such a superfluid, but these were found to be unstable in experiments. Here we show that if weakly interacting atoms are brought suddenly close ("quenched") to such a Feshbach resonance, in the available time before the instability kicks in, they can form a new type of out-of-equilibrium p-wave superfluid which may retain the topological properties of its equilibrium counterpart. We describe the phase diagram of this superfluid and the conditions under which it can be termed topological. The superfluid produced by this quench turns out to be either time-independent and non-topological or of a topological Floquet type.
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