Vortex Pump for Dilute Bose-Einstein Condensates

The formation of vortices by topological phase engineering has been realized experimentally to create the first two- and four-quantum vortices in dilute atomic Bose-Einstein condensates. We consider a similar system, but in addition to the Ioffe-Pritchard magnetic trap we employ an additional hexapole field. By controlling cyclically the strengths of these magnetic fields, we show that a fixed amount of vorticity can be added to the condensate in each cycle. In an adiabatic operation of this vortex pump, the appearance of vortices into the condensate is interpreted as the accumulation of a local Berry phase. Our design can be used as an experimentally realizable vortex source for possible vortex-based applications of dilute Bose-Einstein condensates.

Figure 1

Possible control cycle in the magnetic field parameter space for pumping vortices into a spinor Bose-Einstein condensate (a). Panel (b) displays an example of the temporal changes of the control fields such that the spin at a certain distance from the $z$ axis is reversed with a constant speed. The different parts of the control loop in panel (a) are marked in the top of panel (b).

Figure 2

Particle density and the complex phase of the $|F=1,m_z=-1⟩$ (left columns) and $|F=1,m_z=1⟩$ (right columns) components of the order parameter at half integer multiples of the pumping period $T=360/{\omega }_r$. The field of view is $12a_r\times 12a_r$.

Figure 3

Accumulation of axial angular momentum to the system during (a) adiabatic vortex pumping ($T=360/{\omega }_r$) and (b) pumping without any optical potentials ($T=10/{\omega }_r$), for which the fraction of atoms in the magnetic trap decreases in time as shown. The inset shows the particle density after five full cycles of nonadiabatic pumping with the field of view $12a_r\times 12a_r$.