Symmetry-induced formation of antivortices in mesoscopic superconductors
Recent progress in nanotechnology has stimulated interest in mesoscopic superconductors as components for quantum computing and cryoelectronics. The critical parameters for superconductivity (current and field) of a mesoscopic sample are determined by the pattern of vortices in it, which in turn is...
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Veröffentlicht in: | Nature (London) 2000-12, Vol.408 (6814), p.833-835 |
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Zusammenfassung: | Recent progress in nanotechnology has stimulated interest in mesoscopic
superconductors as components for quantum computing and cryoelectronics. The
critical parameters for superconductivity (current and field) of a mesoscopic
sample are determined by the pattern of vortices in it, which in turn is controlled
by the symmetry imposed by the shape of the sample (see ref.
1 and references therein). Hitherto it has been unclear what happens
when the number of vortices is not consistent with the natural symmetry. Here
we show that additional vortex-antivortex pairs nucleate spontaneously
so as to preserve the symmetry of the sample. For example, in a square with
three vortices, the spontaneously generated pair, along with the original
three vortices, distribute themselves so that the four vortices sit in the
four corners, with the antivortex in the centre. The measured superconducting
phase boundary (of superconducting transition temperature Tc
versus magnetic field strength) is in very good agreement with the calculations,
giving direct experimental evidence for these symmetry-induced vortex-antivortex
pairs. Vortex entry into the sample is also changed: vortices enter a square
in fours, with antivortices generated to preserve the imposed vorticity. The
symmetry-induced nucleation of antivortices is not restricted to superconductors,
but should also apply to symmetrically confined superfluids and Bose-Einstein
condensates. |
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ISSN: | 0028-0836 1476-4687 |
DOI: | 10.1038/35048521 |