114 research outputs found
K-Rb Fermi-Bose mixtures: vortical states and sag
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 for 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.Comment: Submitted to Phys. Rev. A (on May 2004), 15 pages with 3 figure
Interaction-enhanced flow of a polariton persistent current in a ring
We study the quantum hydrodynamical features of exciton-polaritons flowing
circularly in a ring-shaped geometry. We consider a resonant-excitation scheme
in which the spinor polariton fluid is set into motion in both components by
spin-to-orbital angular momentum conversion. We show that this scheme allows to
control the winding number of the fluid, and to create two circulating states
differing by two units of the angular momentum. We then consider the effect of
a disorder potential, which is always present in realistic nanostructures. We
show that a smooth disorder is efficiently screened by the polariton-polariton
interactions, yielding a signature of polariton superfluidity. This effect is
reminiscent of supercurrent in a superconducting loop.Comment: 7 pages, 4 figure
Thermally assisted quantum cavitation in solutions of 3He in 4He
We have investigated the quantum-to-thermal crossover temperature T* for
cavitation in liquid helium mixtures up to 0.05 3He concentrations. With
respect to the pure 4He case, T* is sizeably reduced, to a value below 50 mK
for 3He concentrations above 0.02. As in pure 4He, the homogeneous cavitation
pressure is systematically found close to the spinodal pressure.Comment: Typeset using Revtex, 9 pages and 4 figure
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