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‘Synthetic
Magnetism’
Demonstrated
RESEARCH NEWS FROM THE PFC AT JQI
Yu-Ju Lin, Robert Compton, Karina Jimenez-Garcia, Trey Porto
and Ian Spielman
"Synthetic magnetic fields for ultracold neutral
atoms," Y.-J. Lin, R.L. Compton, K. JimenezGarcia, J.V. Porto and I.B. Spielman, Nature
462, 628 (2009).
For the first time, physicists have used laser
light to create "synthetic magnetism," an exotic
condition in which neutral atoms suddenly begin
to behave as if they were charged particles
interacting with a magnetic field -- even though
no such field is present and the atoms have no
charge. The achievement provides
unprecedented insights into fundamental
physics and the behavior of quantum objects, and opens up entirely new ways to study the nature of condensed-matter
systems that were barely imaginable before. In the experiment, a Bose-Einstein condensate (BEC) of rubidium atoms was
irradiated by two near-infrared (wavelength, λ=801.7 nm) laser beams, oriented at 90 degree angles to each other.
The scientists adjusted the beams to have very slightly different frequencies. The cumulative effect of the two beams, in
conjunction with a weak magnetic bias field, altered the properties of the atoms (in particular, their momentum along one axis)
in a way that depended on their location in the trap and their interaction with the beams. Those differences, the researchers
found, could be tuned by making slight changes in the frequencies of the laser beams, in effect conferring a “charge” on subpopulations of the neutral atoms and creating a synthetic magnetic field to which they reacted. As a result, groups of atoms
began to form vortices within the BEC.