The nanocrystal-carbon cage- interface effect on surface superconductivity in YC2 encapsulated in the multiwall carbon nanocages

The upper critical magnetic field for the vortex state, Hc2, for the bulk crystals YC2 and the critical field for the state of surface superconductivity, Hc3, for the single-crystals YC2 encapsulated in the multiwall carbon nanocages as a function of t (T/Tc, Tc = 3.838 K) are reported. The ratio Hc3/Hc2 increases with increasing t from 1.6 ± 0.2 at t = 0.6 to 2.0 ± 0.3 at t = 0.99. The present data accord with the reported experimental results for the type-II superconductors surrounded by the insulators. The role of the interface between the single-crystal YC2 and the multiwall carbon nanocage in surface superconductivity is discussed in terms of the boundary effects.