K-Rb Fermi-Bose mixtures: Vortex states and sag

D. M. JEZEK, M. BARRANCO, M. GUILLEUMAS, R, MAYOL, AND M. PI

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

The American Physical Society

Lugar: Nueva York; Año: 2004 vol. 70 p. 436301 - 436307

1050-2947

We study a confined mixture of bosons and fermions in the quantal degeneracy regime with attractive boson-fermion interaction. We discuss the effect that the presence of vortical states and the displacement of the trapping potentials may have on mixtures near collapse, and investigate the phase stability diagram of the K-Rb mixture in the mean-field approximation supposing in one case that the trapping potentials felt by bosons and fermions are shifted from each other, as it happens  in the presence of a gravitational sag, and in another case, assuming that the  Bose condensate sustains a vortex state. In both cases, we have obtained an analytical expression fo the fermion effective potential when the Bose condensate is in the Thomas-Fermi regime, that can be used to determine the maxima of the Fermionic density. We have numerically checked that the values one obtains for the location of  these maxima using the analytical formulas remain valid up to the critical boson and fermion numbers, above which the mixture collapses.