Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 37: MLT: Poster Session
TT 37.8: Poster
Donnerstag, 25. März 2010, 14:00–18:00, Poster A
Finite-density corrections to the Unitary Fermi gas: A lattice perspective from DMFT — •Antonio Privitera1,2, Massimo Capone1, and Claudio Castellani1 — 1CRS SMC, CNR-INFM and Dipartimento di Fisica, Universita di Roma La Sapienza, Piazzale Aldo Moro 2, I-00185 Roma, Italy — 2Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, 60438 Frankfurt am Main, Germany
We investigate the approach to the universal regime of the dilute unitary Fermi gas as the density is reduced to zero in a lattice model [1]. To this end we study chemical potential, superfluid order parameter and internal energy of the attractive Hubbard model in three different lattices: a cubic lattice, a Bethe lattice with a semicircular DOS, and a lattice gas with parabolic dispersion and a sharp energy cut-off. The model is solved using Dynamical Mean-Field Theory, that treats directly the thermodynamic limit and arbitrarily low densities, eliminating finite-size effects. The evolution to the low-density limit is smooth and it does not allow to define an unambiguous low-density regime. Such finite-density effects are significantly reduced using the lattice gas, and they are maximal for the cubic lattice. Even though DMFT is bound to reduce to the more standard static mean field in the limit of zero density due to the local nature of the self-energy and of the vertex functions, it compares well with accurate Monte Carlo simulations down to the lowest densities accessible to the latter [2].
[1]A. Privitera et al., arXiv:0909.1298
[2] A. Bulgac et al., Phys. Rev. A 78, 023625 (2008)