Amplitude of the bulk superfluid gap Δ_bulk as a function of the tunnel coupling J and the chemical potential μ calculated for a system of 30 lattice sites with periodic boundary conditions

Figure 2. Amplitude of the bulk superfluid gap Δ_bulk as a function of the tunnel coupling J and the chemical potential μ calculated for a system of 30 lattice sites with periodic boundary conditions. The topological transition corresponds to the lines for which the gap cancels; their location agrees well with the prediction of Kitaev's model μ = ±2J (dashed white lines).

Abstract

We propose an experimental implementation of a topological superfluid with ultracold fermionic atoms. An optical superlattice is used to juxtapose a 1D gas of fermionic atoms and a 2D conventional superfluid of condensed Feshbach molecules. The latter acts as a Cooper pair reservoir and effectively induces a superfluid gap in the 1D system. Combined with a spin-dependent optical lattice along the 1D tube and laser-induced atom tunnelling, we obtain a topological superfluid phase. In the regime of weak couplings to the molecular field and for a uniform gas, the atomic system is equivalent to Kitaev's model of a p-wave superfluid. Using a numerical calculation, we show that the topological superfluidity is robust beyond the perturbative limit and in the presence of a harmonic trap. Finally, we describe how to investigate some physical properties of the Majorana fermions located at the topological superfluid boundaries. In particular, we discuss how to prepare and detect a given Majorana edge state.