'Giant' strengthening of superconducting pairing in metallic nanoclusters: large enhancement of \it{T}_{c} and potential for room-temperature superconductivity

In relation to the recently intensified search for new superconducting systems, it is interesting to study the properties of metal nanoclusters containing $\sim 10^2$–$10^3$ free carriers. It is essential that the spectra of delocalized electrons in many clusters form energy shells similar to those in atoms and nuclei. The superconducting pairing can be very strong if the cluster parameters satisfy certain conditions. Such clusters constitute a new family of high-temperature superconductors (with $T_c\ge 150$ K). Transition into the superconducting state is manifested in an essential rearrangement of the energy spectrum. Pair correlation affects the optical, magnetic, and thermodynamic properties of clusters; corresponding changes can be detected in specific experiments. Clusters can form high-temperature superconducting tunneling networks, and this leads to macroscopic high-temperature superconductivity. In principle, higher values of $T_c$, up to room temperature, may be achieved.