``Giant'' strengthening of superconducting pairing in small metallic nanoparticles: high T$_{c}$ state

The study focuses on metallic nanoclusters containing N$\sim $10$^{2}$-10$^{3}$ free carriers (e.g., Ga$_{56}$, Al$_{45}^{-})$. The delocalized cluster electrons form energy shells similar to those in atoms or nuclei. Under special conditions, superconducting pairing in such nanoclusters can become very strong, and they form a new family of high temperature superconductors. For realistic sets of parameters one can expect a high value of T$_{c}$ (150 K) as well as strong modification of the energy spectrum. In principle, it is possible to raise T$_{c}$ up to room temperature. Specific experiments aimed at detecting the phenomenon of pair correlation in nanoclusters can be proposed: spectroscopy, magnetic, and thermodynamic properties.Transition to the superconducting state of the cluster is accompanied by the peak in its heat capacity. The phenomenon is promising for the creation of high T$_{c}$ superconducting tunneling networks, and hence macroscopic superconductivity.