Universal lower limit on vortex creep in superconductors
Eley at al. propose the existence of a universal minimum realizable S ~ Gi1/2(T/Tc) (Tc is the superconducting transition temperature, and Gi = (γ2/2)[(μ0kBTc)/(4πBc2(0)ξab3(0))]2 ∝ γ2Tc2λ4/ξ2, The Ginzburg number, parameterizes the scale of thermal fluctuations in a superconductor) that has been achieved in our films and few other materials, and is violated by none.
Eley, S., M. Miura, B. Maiorov, and L. Civale, Universal lower limit on vortex creep in superconductors. Nat Mater, 2017. 16(4): p. 409-413.