The superconducting parameters of zero-dimensional In nanoparticles were studied by measuring the magnetic susceptibility, electrical resistivity, and specific heat. Significant alternations of the superconducting parameters were found for particles with diameters smaller than $120\mathrm{nm}$. The Anderson regime, where superconductivity was sharply suppressed by the discrete nature of the electronic levels, was seen for particle smaller than $7.5\mathrm{nm}$. A regime prior to the Anderson one, in which superconductivity was found to vary in accordance with alternations of the structural parameters, due to the small size effect, was also observed and characterized. A nonignorable 5 % increase in $T_C$ and a 400 times higher $H_C$ were seen for the $39\mathrm{nm}$ particles. The appearance of this regime was closely related to the structural symmetry of the system.

• Received 14 June 2005

DOI:https://doi.org/10.1103/PhysRevB.72.214516