Temperature dependence of upper critical fields and coherence lengths for optimally-doped YBa2Cu3O7–δ thin films
E. V. Petrenko, L. V. Omelchenko, A. V. Terekhov, Yu. A. Kolesnichenko, K. Rogacki, Daulet Sergeyev, A. L. Solovjov
Abstract
We report the comprehensive comparative analysis of the upper critical magnetic fields μHc2(0) obtained within Ginzburg–Landau (GL) and Werthamer–Helfand–Hohenberg (WHH) theories for optimally-doped YBa2Cu3O7–δ thin films. For different orientations of the magnetic field, our calculations give 638 and 153 T for μHc2(0), H || ab and μHc2(0), H || c, respectively, when using Hc2(0). For the first time, the temperature dependences of coherence lengths ξab(T) and ξc(T) within proposed theories were determined using 50 and 90% criteria of the normal state resistivity value ρN. The GL (0.9ρN) approach gives ξab(0) = 11.8 Å and ξc(0) = 3.0 Å which are in a good agreement with literature data. The implications of very short coherence lengths in HTSCs are discussed.