Dilation of the Giant Vortex State in a Mesoscopic Superconducting Loop

We have experimentally investigated the magnetization of a mesoscopic aluminum loop at temperatures well below the superconducting transition temperature ${T}_{c}.$ The flux quantization of the superconducting loop was investigated with a $\ensuremath{\mu}$-Hall magnetometer in magnetic field intensities between $\ifmmode\pm\else\textpm\fi{}100 \mathrm{G}.$ The magnetic field intensity periodicity observed in the magnetization measurements is expected to take integer values of the superconducting flux quanta ${\ensuremath{\Phi}}_{0}=h/2e.$ A closer inspection of the periodicity, however, reveals a subflux quantum shift. This fine structure we interpret as a consequence of a so-called giant vortex state nucleating towards either the inner or the outer side of the loop. These findings are in agreement with recent theoretical reports.