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

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Cited by in corpus (14)

• Auxiliary Field quantum Monte Carlo for Strongly Paired Fermions
• Ground state energy of dilute neutron matter at next-to-leading order in lattice chiral effective field theory
• Lattice calculations for A=3,4,6,12 nuclei using chiral effective field theory
• Lattice chiral effective field theory with three-body interactions at next-to-next-to-leading order
• Quantum Monte Carlo approaches to nuclear and atomic physics
• 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
• Precision benchmark calculations for four particles at unitarity
• The symmetric heavy-light ansatz
• Temperature-dependent errors in nuclear lattice simulations
• Universal dimer-dimer scattering in lattice effective field theory
• Superfluid Condensate Fraction and Pairing Wave Function of the Unitary Fermi Gas
• Working Group Summary: Chiral Dynamics in Few-Nucleon Systems