Detection of discretized single-shell penetration in mesoscopic vortex   matter
  We investigated configurational changes in mesoscopic vortex matter with less than thousand vortices during flux penetration in freestanding 50 $\mu$m diameter disks of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8 +\delta}$. High-resolution AC and DC local magnetometry data reveal oscillations in the transmittivity echoed in peaks in the third-harmonics magnetic signal fainting on increasing vortex density. By means of extra experimental evidence and a simple geometrical analysis we show that these features fingerprint the discretized entrance of single-shells of vortices having a shape that mimics the sample edge. 
Moira In\'es Dolz, Yanina Fasano, N\'estor Ren\'e Cejas Bolecek,   Hern\'an Pastoriza, Marcin Konczykowski and Cornelius Jac...
cond-mat.supr-con cond-mat.mes-hall