The presence of giant diamagnetism in Au nanorods, NRs, is shown to be a possible consequence of field induced currents in the surface electrons. The distance, Delta , between quantum surface energy levels has been calculated as a function of the NRs radius. Note that those electrons occupying states for which Delta > k(B)T are steadily orbiting with constant orbital moment. The diamagnetic response induced when a field is turned on remains constant during the time the field is acting. As the NRs radius increases, Delta decreases and accordingly the electron fraction available to generate constant currents decreases, consequently the surface diamagnetic susceptibility decreases towards its bulk value. The surface electronic motion induced by the axial applied field on electrons confined into a cylindrical surface accounts with extremely good quantitative agreement for the giant diamagnetism recently measured and reported.

We gratefully acknowledge financial support from the Spanish Ministerio de Innovacion, Ciencia y Tecnologia (grant numbers MAT2012-37109-C02-01 and FIS2010-21282-C02-02), the University of the Basque Country (grant no. IT-366-07), the Basque Government through the NANOMATERIALS project (grant IE05-151) under the ETORTEK Program (iNanogune). AH acknowledges to Dr J M Rojo helpful comments on gold surfaces.