2009/10/31 by W. R. Schneider, William Schneider, Mohit Randeria · 81 citations
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Fermi Gamma-ray Space Telescope #Fermi gas #Ground state #Momentum (technical analysis) #Observable #Omega #Pairing #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Quantum, superfluid, helium dynamics #Superconductivity #Superfluidity #Unitarity #cond-mat.quant-gas
paper · pdf · doi:10.1103/physreva.81.021601
published in Physical Review A 81(2) (American Physical Society) · 4 pages, 4 figures
openalex publication_date 2010/02/03 · arxiv created 2010/02/05 · arxiv updated 2010/02/08 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We show that the universal 1/k4 tail in the momentum distribution of dilute Fermi gases implies that the spectral function A(k,\ensuremathω) must have weight below the chemical potential for large momentum k\ensuremath≫kF, with observable consequences in radio-frequency spectroscopy experiments. We find that this incoherent spectral weight is centered around \ensuremathω\ensuremath≃\ensuremath-\ensuremathε(k) in a range of energies of order vFk. This ``bending back'' in the dispersion, while natural for superfluids, is quite surprising for normal gases. This universal structure is present in the hard-sphere gas as well as in the Fermi-liquid ground state of the highly imbalanced, attractive gas near unitarity. We argue that, even in the BCS superfluid, this bending back at large k is dominated by interaction effects which do not reflect the pairing gap.