Observation of Dirac monopoles in a synthetic magnetic field.
Magnetic monopoles--particles that behave as isolated north or south magnetic poles--have been the subject of speculation since the first detailed observations of magnetism several hundred years ago. Numerous theoretical investigations and hitherto unsuccessful experimental searches have followed Dirac's 1931 development of a theory of monopoles consistent with both quantum mechanics and the gauge invariance of the electromagnetic field. The existence of even a single Dirac magnetic monopole would have far-reaching physical consequences, most famously explaining the quantization of electric charge. Although analogues of magnetic monopoles have been found in exotic spin ices and other systems, there has been no direct experimental observation of Dirac monopoles within a medium described by a quantum field, such as superfluid helium-3 (refs 10-13). Here we demonstrate the controlled creation of Dirac monopoles in the synthetic magnetic field produced by a spinor Bose-Einstein condensate. Monopoles are identified, in both experiments and matching numerical simulations, at the termini of vortex lines within the condensate. By directly imaging such a vortex line, the presence of a monopole may be discerned from the experimental data alone. These real-space images provide conclusive and long-awaited experimental evidence of the existence of Dirac monopoles. Our result provides an unprecedented opportunity to observe and manipulate these quantum mechanical entities in a controlled environment.
Department of Physics, Amherst College, Amherst, Massachusetts 01002-5000, USA.
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MW
Ray
QCD Labs, COMP Centre of Excellence, Department of Applied Physics, Aalto University, PO Box 13500, 00076 Aalto, Finland.
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E
Ruokokoski
1] Department of Physics, Amherst College, Amherst, Massachusetts 01002-5000, USA [2] City of Hope National Medical Center, 1500 East Duarte Road, Duarte, California 91010, USA.
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S
Kandel
1] QCD Labs, COMP Centre of Excellence, Department of Applied Physics, Aalto University, PO Box 13500, 00076 Aalto, Finland [2] Low Temperature Laboratory (OVLL), Aalto University, PO Box 13500, 00076 Aalto, Finland.
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M
Möttönen
Department of Physics, Amherst College, Amherst, Massachusetts 01002-5000, USA.
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Hall