2019/10/31 by Rongzheng He, Ning Li, Bing-Nan Lu +1
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Fermi Gamma-ray Space Telescope #Fermi gas #Fermion #Pairing #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Quantum, superfluid, helium dynamics #Scattering #Scattering length #Superconductivity #Superfluidity #Wave function #cond-mat.quant-gas #hep-lat #nucl-th
paper · pdf · doi:10.1103/physreva.101.063615
published as Phys. Rev. A 101, 063615 (2020) · 12 pages and 11 figures, final version to appear Physical Review A
openalex created_date 2019/10/10 · arxiv created 2020/06/01 · openalex publication_date 2020/06/11 · arxiv updated 2020/07/02 · openalex updated_date 2026/08/05
The unitary Fermi gas is a many-body system of two-component fermions with zero-range interactions tuned to infinite scattering length. Despite much activity and interest in unitary Fermi gas and its universal properties, there have been great difficulties in performing accurate calculations of the superfluid condensate fraction and pairing wave function. In this paper, we present auxiliary-field lattice Monte Carlo simulations using a lattice interaction which accelerates the approach to the continuum limit, thereby allowing for robust calculations of these difficult observables. As a benchmark test, we compute the ground-state energy of 33 spin-up and 33 spin-down particles. As a fraction of the free Fermi gas energy EFG, we find E0/EFG=0.369(2),0.372(2), using two different definitions of the finite-system energy ratio, in agreement with the latest theoretical and experimental results. We then determine the condensate fraction by measuring off-diagonal long-range order in the two-body density matrix. We find that the fraction of condensed pairs is \ensuremathα=0.43(2). We also extract the pairing wave function and find the pair correlation length to be \ensuremathζpkF=1.8(3)\ensuremathℏ, where kF is the Fermi momentum. Provided that the simulations can be performed without severe sign oscillations, the methods we present here can be applied to superfluid neutron matter as well as more exotic P-wave and D-wave superfluids.