Физика Низких Температур: Том 47, Выпуск 12 (Декабрь 2021), c. 1148-1156 ( к оглавлению , назад )
Study of fluctuation conductivity in YBa2Cu3O7–δ films in strong magnetic fields
E. V. Petrenko1, L. V. Omelchenko1, Yu. A. Kolesnichenko1, N. V. Shytov1, K. Rogacki2, D. M. Sergeyev3, and A. L. Solovjov1,4
1B. Verkin Institute for Low Temperature Physics and Engineering of NAS of Ukraine, Kharkiv 61103, Ukraine
2Institute for Low Temperatures and Structure Research, Polish Academy of Sciences, Wroclaw 50-950, Poland
3K. Zhubanov Aktobe Regional State University, Aktobe 030000, Kazakhstan
4The Faculty of Physics, V. N. Karazin Kharkiv National University, Kharkiv 61022, Ukraine
Received July 20, 2021, published online October 25, 2021
We report the effect of the ab-plane magnetic field B up to 8 T on the resistivity ρ(T) and fluctuation conductivity σʹ(T) in YBa2Cu3O7–δ thin films. As expected, up to ~ 2.5 T the magnetic field monotonously increases ρ, the width of the resistive transition, ΔTc, and coherence length along the c axis, ξс(0), but decreases both Tc and the range of superconducting (SC) fluctuations ΔТfl. The fluctuation conductivity exhibits a crossover at characteristic temperature T0 from the 3D Aslamasov–Larkin (AL) theory near Tc to the 2D fluctuation theory of Maki–Thompson (MT). However, at B = 3 T, the MT term is completely suppressed, and above T0 σʹ(T) is unexpectedly described by the fluctuation contribution of 2D AL, suggesting the formation of a 2D vortex lattice in the film under the action of a magnetic field. At the same time, ΔТfl sharply increases by a factor of about 7, and ξс(0) demonstrates a very unusual dependence on Tc when B increases above 3 T. Our results demonstrate the possibility of the formation of a vortex state in YBCO and its evolution with increasing B.
Key words: high-temperature superconductors, YBCO films, excess conductivity, fluctuation conductivity, magnetic field, coherence length.