Reentrant orbital effect against superconductivity in the quasi-two-dimensional superconductor NbS₂

We derive integral equation for superconducting gap, which takes into account the quantum nature of electron motion in a

parallel magnetic field in a quasi-two-dimensional (Q2D) superconductor in the presence of a non-zero perpendicular field

component. By comparison of our theoretical results with the recent experimental data obtained on the NbS₂, we show that the

orbital effect against superconductivity  partially destroys superconductivity in the so-called Ginzburg-Landau area of this

Q2D conductor, as expected. Nevertheless, at relatively high magnetic fields, H > 15 T, the orbital effect

starts to improve the Fulde-Ferrell-Larkin-Ovchinnikov phase in the NbS₂, due to the quantum nature of electron motion in a

parallel magnetic field. In our opinion, this is the most clear demonstration that the orbital effect against superconductivity

in a parallel magnetic field has a reentrant nature.