3 ms·
As far as I understand it (not an expert on these things), flux pinning is caused by microscopic defects that allow the magnetic field to penetrate at certain p
by zarzavat 3y ago
As far as I understand it (not an expert on these things), flux pinning is caused by microscopic defects that allow the magnetic field to penetrate at certain points. An idealized superconductor that is perfectly uniform expels the magnetic field at all points and so would not display the effect, it would simply be diamagnetic. So it’s mistaken and somewhat perverse to view the absence of flux pinning as proof that something is not a superconductor.
In the case of LK99, the claim is that it does not show flux pinning because the sample is impure and not uniformly superconductive, i.e. it is not expelling the magnetic field enough.
- jamesmaniscalco 3y agoNo defects needed for flux penetration in a type-II superconductor. When the conference length is smaller than the penetration depth (up to a factor of sqrt(2)), flux vortices can nucleate as soon as the surface magnetic field gets above the lower critical field Bc1.
- jamesmaniscalco 3y agoSorry, that should say “coherence length”.
- jacquesm 3y agoThat also explains - assuming it is all true - the lack of current through the sample.