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 Tc. The flux quantization of the superconducting loop was investigated with a μ-Hall magnetometer in magnetic field intensities between ±100 G. The magnetic field intensity periodicity observed in the magnetization measurements is expected to take integer values of the superconducting flux quanta Φ₀=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.