Vortices in Spinor Bose-Einstein Condensates
- Started
- 14th July 2009
- Research Team
- Justin Lovegrove
- Investigators
- Janne Ruostekoski
Density isosurfaces for three spin components in a vortex system. The density minima are in different places and so the total density is never zero.
A Bose-Einstein Condensate (BEC) is formed when a dilute atomic gas is cooled to near absolute zero, and is described precisely by quantum mechanics. This enables quantum-mechanical phenomena to be observed on the macroscopic scale, such as the formation of quantised vortices. A quantised vortex is an example of a topological defect - an object that can never be destroyed by local deformation. In other words, the vortex will continue swirling forever, unlike in classical fluids. In simple BECs, the density inside the vortex is zero, just as in a vortex in a rotating bucket of water. When atomic spin degrees of freedom are included, new vortex structures become possible, including some in which the core of the vortex fills with BEC atoms.
To study these systems we numerically solve coupled, nonlinear PDEs in 3+1 dimensions, usually requiring a 64^3 spatial grid and 10^6 iterations in time. With Iridis, we are able to run many such simulations in parallel, enabling us to study vortices over a wide parameter space. This enables us to identify which vortices can be found under various experimental conditions, enabling a probe of fundamentally quantum-mechanical physics in the laboratory.
As well as the intrinsic significance of quantised vortices, their existence as experimentally realisable topological defects gives them great value across a wide range of fields. Analogies with other topological defects, notably cosmological magnetic field lines, vortices in neutron stars and cosmic strings predicted in models of early universe cosmology, may enable experimental studies to shed light on physics which has until now been inaccessible in the laboratory.
Categories
Physical Systems and Engineering simulation: Superfluidity
Algorithms and computational methods: FFT
Programming languages and libraries: Fortran, Matlab, OpenMP