Experimental determination of the number of flux lines trapped by micro-holes in superconducting samples

Abstract

The influence of a periodic landscape of pinning sites on the vortex dynamics in Pb thin films is explored by ac-susceptibility measurements. For different amplitudes h of the ac-drive, the ac-susceptibility x=x'+ix'' exhibits a complex field dependence associated with different dynamic regimes. At very low ac-drives where both, multiquanta vortices trapped by the antidots and interstitial vortices oscillate inside the pinning potential (intra-valley motion), a small kink in x'(H) together with a very low dissipation is observed. At intermediate ac-excitations such that vortices in the antidots remain pinned whereas interstices are driven out of the pinning well, a more pronounced kink in the screening coinciding with the onset of dissipation (x''(H) ~ 0) indicates the entrance of interstitial vortices. Eventually, at high enough amplitudes all vortices are set in motion and the penetration of interstitial vortices appears as a sudden reduction of the shielding power. We show that these distinctive features allow us to clearly identify the maximum number of flux quanta per hole regardless the vortex dynamic regime.

6 pages, 3 figures, to be published in Phys. Rev. B

References in corpus (4)

• Guided vortex motion in superconductors with a square antidot lattice
• Anisotropic vortex pinning in superconductors with a square array of rectangular submicron holes
• Field-dependent Vortex Pinning Strength in a Periodic Array of Antidots
• Lock-in to commensurate states induced by a periodic array of nanoscale anti-dots in Nb superconductor

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