Vortex observation by MOKE microscopy has been previously reported in Nb (see http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-17-18-16160). Cuprates would have comparable to Nb magnetic penetration depth, so I wonder why there is no reports in literature with this regards.
Is it question of resolution, or some other fundamental obstacle?
And in the case I've missed such report, please send me a link. Thanks.
Dear Behnam, the paper you are referring to reports observation of vortices by STS, and I know a number of reports of this kind of measurements, as well as Hall or Lorentz microscopy.
However the question was about particular technique Magneto Optical Kerr Effect (MOKE). The technique implies sputtering of magneto-optical material (e.g. EuSe) on the surface of the superconductor.There are only couple of reports on conventional type II superconductors to the best of my knowledge only Nb and NbSe (see for instance http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-17-18-16160).
I wonder why is it so, and why there are no reports on cuprates?
Dear Behnam, I think, because we are talking about magnetically induced changes in optical constants, that relevant length scale for MOKE would be magnetic penetration depth which is of the order of 100s of nm. The intervortex distance would be defined by external field (in ideal Abrikosov lattice) - roughly number of vortices is the number of flux quanta in the total magnetic flux passing through the sample. So at low fields where density of vortices is low and close to Tc where magnetic penetration depth is large vortices should be observed.
Dear Behnam, the way I see one can deal with average effect is to use small fields so one will have low vortex density and consequently will be able to resolve them. I would believe apart from weak interplane coupling and high-Tc, cuprates would be quite the same as niobium from the point of view of this experiment.