Influence of thermal fluctuations on single-vortex pinning in Rb3C60 fullerene superconductors.

From the experimentally obtained H(T) dependence of the transition boundary between short-range and long-range vortex order for ${\mathrm{Rb}}_{3}$${\mathrm{C}}_{60}$ superconductors, the temperature dependences of the effective potential barrier for pinning of a single vortex on a pinning center and the effective pinning force are calculated. It is shown that the effective barrier falls almost linearly with the increase of temperature and that the harmonic thermal fluctuations strongly decrease the effective pinning force as ${\mathit{T}}^{3/2}$.