Two-dimensional Berezinskii–Kosterlitz–Thouless topological phase transition in three-dimensional Bi2Sr2Ca2Cu3O10+x:(La,Sr)MnO3 nanocomposites
A. I. D’yachenko
G. V. Kurdyumov Institute of Metal Physics of the National Academy of Sciences of Ukraine, Kyiv 03142, Ukraine
V. N. Krivoruchko and V. Yu. Tarenkov
O. O. Galkin Donetsk Institute for Physics and Engineering of the National Academy of Sciences of Ukraine Kyiv 03028, Ukraine
Received February 13, 2021, revised March 11, 2021, published online April 26, 2021
Electrical transport properties of random binary networks composed of high-Tc superconductor Bi2Sr2Ca2Cu3O10+x(Bi2223) microparticles and half-metal ferromagnet La2/3Sr1/3MnO3 (LSMO) nanoparticles have been investigated. The experimental current-voltage characteristics of bulk samples of nanocomposites with a volumetric content of 4:1 components are well described by the Berezinsky–Kosterlitz–Thouless (BKT) model for two-dimensional (2D) superconductors undergoing a superconducting transition. The observed 2D-like behavior of the three-dimensional transport properties of the nanocomposite is most likely associated with two different physical spatial scales involved in the formation of the properties of the nanocomposite: a significant difference between the geometric dimensions of the constituent components and the appearance of a triplet superconducting state induced by the proximity effect in semimetallic manganite LSMO contacting Bi2223. Below the Bi2223 superconducting transition temperature, bulk resistive losses in the nanostructures are determined by the current flowing through ferromagnetic LSMO nanoparticles that cover Bi2223 microgranules. As temperature decreases, proximity-induced superconducting transition in the effectively 2D surface of LSMO nanoparticles covering Bi2223 microgranules reveals itself as the topological BKT-like superconducting transition in the bulk sample.
Key words: superconductor-ferromagnet nanostructures, the Berezinskii–Kosterlitz–Thouless transition.