Effects of collisions against thermal impurities in the dynamics of a trapped fermion gas
- INFM-NEST and Classe di Scienze, Scuola Normale Superiore, I-56126 Pisa (Italy)
- Istituto per le Applicazioni del Calcolo, CNR, Viale del Policlinico 137, I-00161 Rome (Italy)
We present a theoretical study of the dynamical behavior of a gas made of ultracold fermionic atoms, which during their motions can collide with a much smaller number of thermal bosonic impurities. The atoms are confined inside harmonic traps and the interactions between the two species are treated as due to s-wave scattering with a negative scattering length modeling the {sup 40}K-{sup 87}Rb fermion-boson system. We set the fermions into motion by giving a small shift to their trap center and examine two alternative types of initial conditions, referring to (i) a close-to-equilibrium situation in which the two species are at the same temperature (well below the Fermi temperature and well above the Bose-Einstein condensation temperature); and (ii) a far-from-equilibrium case in which the impurities are given a Boltzmann distribution of momenta while the fermions are at very low temperatures. The dynamics of the gas is evaluated by the numerical solution of the Vlasov-Landau equations for the one-body distribution functions, supported by some analytical results on the collisional properties of a fermion gas. We find that the trapped gaseous mixture is close to the collisionless regime for values of the parameters corresponding to current experiments, but can be driven towards a collisional regime even without increasing the strength of the interactions, either by going over to heavier impurity masses or by matching the width of the momentum distribution of the impurities to the Fermi momentum of the fermion gas.
- OSTI ID:
- 20646417
- Journal Information:
- Physical Review. A, Vol. 70, Issue 4; Other Information: DOI: 10.1103/PhysRevA.70.043623; (c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ATOM-ATOM COLLISIONS
ATOMS
BOLTZMANN-VLASOV EQUATION
BOSE-EINSTEIN CONDENSATION
BOSONS
DISTRIBUTION
DISTRIBUTION FUNCTIONS
EQUILIBRIUM
FERMIONS
IMPURITIES
MIXTURES
NUMERICAL ANALYSIS
NUMERICAL SOLUTION
POTASSIUM 40
RUBIDIUM 87
S WAVES
SCATTERING
SCATTERING LENGTHS
SIMULATION
TRAPPING
TRAPS