Can superconductivity persist in arbitrarily small particles?

The study of superconductivity in nanostructured systems is particularly fascinating due to the existence of a multitude of length scales, such as the coherence length (ξ) and the penetration depth (λL), each of which could have a role to play in finite size effects. However, in quasi-zero dimensional superconductors, such as isolated nanoparticles or nanocrystalline solids, superconductivity usually persists down to length scales much smaller than ξ and λL. Ultimately, the lower size limit (d_C) for superconducting order to exist is set by the Anderson criterion, which arises from quantum confinement and is believed to be remarkably accurate and universal. Though the actual nature of the size dependence of T_C and H_C2 are quite different in superconductors with weak, intermediate and strong coupling strengths, it has still been observed that T_C → 0 as the particle size d → d_C. Reported herewith is a recent result that questions the validity of the Anderson criterion