SUPPRESSION OF SUPERCONDUCTIVITY IN HYBRID STRUCTURES

Materials that possess strong spin-orbit interaction have provoked great interest over the past few years, in particular, in the actively developing field of quantum calculations. A topological insulator is a good example of such a material. The topological insulator has high surface conductivity, whereas in the body it shows the properties of an insulator, this being a purely phenomenological definition of a substance. Superconducting hybrid structures also present a promising elemental basis for quantum calculations and spintronics. This paper considers hybrid nanostructures like superconductor/ ferromagnet/ superconductor (S/F/S) and superconductor/ topological insulator/ superconductor (S/TI/S), where a uniform magnetic field is imposed onto the surface of the topological insulator. The paper investigates the behaviour of critical temperature in the superconducting layer Тс depending on different parameters of the systems, in particular, the dependence of Тс on the thickness of the layer dn in the topological insulator TI (or the ferromagnetic layer F). To solve the problem, we use the formalism of the quasiclassical Green's functions . The model assumes a diffusion mode, which holds true when the electron free path length is much less than the characteristic scale of the system. As a rule, such a limit is easier to be performed, since the commonly made structures have admixtures. To solve the problem on self-consistency of the superconducting energetic slot D we use a unimode approximation. As the results of our calculations, we give curves of the critical temperature behaviour in the systems under consideration. It is demonstrated that while the critical temperature exhibits a nonmonotonic behaviour and can make oscillations because of phase 0 -p transitions in the S/F/S structures, in the S/TI/S structures the temperature of the superconducting transition exhibits a trivial behaviour characterized by the monotonic attenuation.