  Currently, the superconducting diode effect (SDE) is actively discussed due to large application potential in superconducting electronics. In particular, the superconducting hybrid structures based on three-dimensional (3D) topological insulators are among the best candidates due to the strongest spin-orbit coupling (SOC). Most of the theoretical studies of the SDE focus either on full numerical calculation, which is often rather complicated or on the phenomenological approach. In the present paper we perform a comparison of the linearized and nonlinear microscopic approaches in the superconductor/ ferromagnet/ 3D topological insulator (S/F/TI) hybrid structure. Employing the quasiclassical Green's function formalism we solve the problem self-consistently. We show that the results obtained by the linearized approximation are not qualitatively different from the nonlinear solution. Main distinction in the results between the two methods is quantitative, i. e. they yield different supercurrent amplitudes. However, when calculating the so-called diode quality factor the quantitative difference is eliminated and both approaches can result in a good agreement. 
Superconducting diode effect in topological hybrid structures