17 research outputs found
Superradiant Laser: First-Order Phase Transition and Non-stationary Regime
We solve the superradiant laser model in two limiting cases. First the
stationary low-pumping regime is considered where a first-order phase
transition in the semiclassical solution occurs. This discontinuity is smeared
out in the quantum regime. Second, we solve the model in the non-stationary
regime where we find a temporally periodic solution. For a certain parameter
range well separated pulses may occur.Comment: RevTeX, 10 pages, 4 figure
Coherence properties of spinor condensates at finite temperatures
We consider a spinor condensate of 87Rb atoms in its F=1 hyperfine state at
finite temperatures. Putting initially all atoms in m_F=0 component we find
that the system evolves into the state of thermal equilibrium. This state is
approached in a step-like process and when established it manifests itself in
distinguishable ways. The atoms in states m_F=+1 and m_F=-1 start to rotate in
opposite directions breaking the chiral symmetry and showing highly regular
spin textures. Also the coherence properties of the system changes
dramatically. Depending on the strength of spin-changing collisions the system
first enters the stage where the m_F=+1 and m_F=-1 spinor condensate components
periodically loose and recover their mutual coherence whereas their thermal
counterparts get completely dephased. For stronger spin changing collisions the
system enters the regime where also the strong coherence between other
components is built up.Comment: 5 pages, 4 figure
Solitons and vortices in ultracold fermionic gases
We investigate the possibilities of generation of solitons and vortices in a
degenerate gas of neutral fermionic atoms. In analogy with, already
experimentally demonstrated, technique applied to gaseous Bose-Einstein
condensate we propose the phase engineering of a Fermi gas as a practical route
to excited states with solitons and vortices. We stress that solitons and
vortices appear even in a noninteracting fermionic gas. For solitons, in a
system with sufficiently large number of fermions and appropriate trap
configuration, the Pauli blocking acts as the interaction between particles.Comment: 4 pages, 5 figures many new result