Multiband effects on the Fulde-Ferrell-Larkin-Ovchinnikov state in superconducting metallic nanofilms

TL;DR

This paper investigates how multiband effects and quantum confinement influence the stability and phase diagram of the FFLO state in superconducting nanofilms, revealing oscillatory behavior and phase segmentation.

Contribution

It provides a detailed analysis of the interplay between multiband effects, shape resonances, and FFLO phase stability in superconducting nanofilms, highlighting new oscillatory phenomena.

Findings

FFLO phase stability oscillates with film thickness.

Multiband effects divide the FFLO stability region into subregions.

Phase shift of FFLO oscillations is half the period of critical field oscillations.

Abstract

In superconducting nanofilms the energy quantization induced by the confinement in the direction perpendicular to the film leads to a multiband character of the system which results in the thickness-dependent oscillations of the in-plane critical field (shape resonances). In this paper, we study the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) phase in nanofilms and examine its interplay with the shape resonances as well as the influence of the multiband effects on its stability. We demonstrate that the range of the magnetic field for which the FFLO state is stable oscillates as a function of the film thickness with the phase shift equal to one half of the period corresponding to the critical magnetic field oscillations. Moreover, the multiband effects lead to a division of the FFLO phase stability region into subregions number of which depends on the number of bands participating in the formation of the paired state.