Superfluidity and excitations at unitarity

Abstract

We present lattice results for spin-1/2 fermions at unitarity, where the effective range of the interaction is zero and the scattering length is infinite. We measure the spatial coherence of difermion pairs for a system of 6, 10, 14, 18, 22, 26 particles with equal numbers of up and down spins in a periodic cube. Using Euclidean time projection, we analyze ground state properties and transient behavior due to low-energy excitations. At asymptotically large values of t we see long-range order consistent with spontaneously broken U(1) fermion-number symmetry and a superfluid ground state. At intermediate times we see exponential decay in the t-dependent signal due to an unknown low-energy excitation. We probe this low-energy excitation further by calculating two-particle correlation functions. We find that the excitation has the properties of a chain of particles extending across the periodic lattice.

40 pages, 19 figures, revised version includes new data on two-particle density correlations

References in corpus (5)

• Vortices and Superfluidity in a Strongly Interacting Fermi Gas
• Observation of the Pairing Gap in a Strongly Interacting Fermi Gas
• Crossover from a molecular Bose-Einstein condensate to a degenerate Fermi gas
• General coordinate invariance and conformal invariance in nonrelativistic physics: Unitary Fermi gas
• Critical Temperature and Thermodynamics of Attractive Fermions at Unitarity

Cited by in corpus (5)

• Lattice chiral effective field theory with three-body interactions at next-to-next-to-leading order
• The ground state energy at unitarity
• Two-particle scattering on the lattice: Phase shifts, spin-orbit coupling, and mixing angles
• Dilute neutron matter on the lattice at next-to-leading order in chiral effective field theory
• Temperature-dependent errors in nuclear lattice simulations