We have shown how the superconducting energy gap can be enhanced by ~60% from its bulk value in superconducting nanoparticles of Sn which are at the limit of superconductivity for a zero dimensional system. Though the occurrence of these ‘shell effects’ which originates from quantum confinement had been predicted theoretically, our experiments on single, isolated Sn nanoparticles by a scanning tunneling microscope show for the first time in a real system that the superconducting energy gap is very sensitive on the particle size and shape and very small changes can cause large oscillations in its value, leading to huge enhancements.
Nature Materials 9, 550 (2010) Article highlighted in
We reported direct experimental evidence of thermal fluctuations and the gradual breakdown of superconductivity in Pb nanoparticles as the size is reduced. The experimental data was well described by a theoretical model. Thermal fluctuations give rise to a finite energy gap or “fluctuation dominated regime” around Tc. Our results are a first step to understand quantitatively the evolution of superconductivity with particle size and the role of thermal fluctuations for single small superconductors.
Phys. Rev. B. 84, 104525 (2011) Article