We report a detailed scanning tunneling microscopy study of a superconductor in a strong vortex confinement regime. This is achieved in a thin nano-island of Pb having a size d about 2-3 times the effective coherence length, and a thickness h such that h << d << λ , where λ is the effective London penetration depth. In this geometry the magnetic field evolution of local tunneling spectra reveals only two superconducting configurations to exist: zero and single vorticity. The normal state is reached at HC ≈ 0.46 T, about 6 times the critical field of bulk Pb, with no higher order vorticity observed . The comparison of the acquired Scanning Tunneling Spectroscopy data with the numerically resolved Usadel equations allowed us to reveal the fundamental role played in both configurations by the circulating supercurrents.
 T. Cren et al., Phys. Rev. Lett. 102, 127005 (2009).