15 research outputs found
Dynamics of the modified Kibble-\.Zurek mechanism in antiferromagnetic spin-1 condensates
We investigate the dynamics and outcome of a quantum phase transition from an
antiferromagnetic to phase separated ground state in a spin-1 Bose-Einstein
condensate of ultracold atoms. We explicitly demonstrate double universality in
dynamics within experiments with various quench time. Furthermore, we show that
spin domains created in the nonequilibrium transition constitute a set of
mutually incoherent quasicondensates. The quasicondensates appear to be
positioned in a semi-regular fashion, which is a result of the conservation of
local magnetization during the post-selection dynamics
Double universality of a quantum phase transition in spinor condensates: the Kibble-\.Zurek mechanism and a conservation law
We consider a phase transition from antiferromagnetic to phase separated
ground state in a spin-1 Bose-Einstein condensate of ultracold atoms. We
demonstrate the occurrence of two scaling laws, for the number of spin
fluctuations just after the phase transition, and for the number of spin
domains in the final, stable configuration. Only the first scaling can be
explained by the standard Kibble-\.Zurek mechanism. We explain the occurrence
of two scaling laws by a model including post-selection of spin domains due to
the conservation of condensate magnetization
Spinor condensate of Rb as a dipolar gas
We consider a spinor condensate of Rb atoms in F=1 hyperfine state
confined in an optical dipole trap. Putting initially all atoms in
component we find that the system evolves towards a state of thermal
equilibrium with kinetic energy equally distributed among all magnetic
components. We show that this process is dominated by the dipolar interaction
of magnetic spins rather than spin mixing contact potential. Our results show
that because of a dynamical separation of magnetic components the spin mixing
dynamics in Rb condensate is governed by dipolar interaction which plays
no role in a single component rubidium system in a magnetic trap
Nonadiabatic quantum phase transition in a trapped spinor condensate
We study the effect of an external harmonic trapping potential on an outcome of the nonadiabatic quantum phase transition from an antiferromagnetic to a phase-separated state in a spin-1 atomic condensate. Previously, we demonstrated that the dynamics of an untrapped system exhibits double universality with two different scaling laws appearing due to the conservation of magnetization. We show that in the presence of a trap, double universality persists. However, the corresponding scaling exponents are strongly modified by the transfer of local magnetization across the system. The values of these exponents cannot be explained by the effect of causality alone, as in the spinless case. We derive the appropriate scaling laws based on a slow diffusive-drift relaxation process in the local density approximation