Effects of trap anisotropy on the impurity scattering regime in a Fermi gas

P. CAPUZZI, P. VIGNOLO, AND M. P. TOSI

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

Año: 2005 vol. 72 p. 13618 - 136186

1050-2947

We evaluate the low-lying oscillation modes and the ballistic expansion properties of a harmonically trapped gas of fermionic 40K atoms containing thermal 87Rb impurities as functions of the anisotropy of the trap. Numerical results are obtained by solving the Vlasov-Landau equations for the one-body phase-space distri- bution functions and are used to test simple scaling Ansätzes. Starting from the gas in a weak impurity- scattering regime inside a spherical trap, the time scales associated to motions in the axial and azimuthal directions enter into competition as the trap is deformed to an elongated cigarlike shape. This competition gives rise to coexistence of collisionless and hydrodynamic behaviors in the low-lying surface modes of the gas as well as to a dependence of the aspect ratio of the expanding cloud on the collision time.