Orbital effect on the in‐plane critical field in free‐standing superconducting nanofilms

Abstract

The superconductor to normal metal phase transition induced by the in‐plane magnetic field is studied in free‐standing Pb(111) nanofilms. In the considered structures, the energy quantization induced by the confinement leads to the thickness‐dependent oscillations of the critical field (the so‐called “shape resonances”). In this paper, we examine the influence of the orbital effect on the in‐plane critical magnetic field in nanofilms. We demonstrate that the orbital term suppresses the critical field and reduces the amplitude of the thickness‐dependent critical field oscillations. Moreover, due to the orbital effect, the slope Hnormalc,false|false|−Tc at Tcfalse(0false) becomes finite and decreases with increasing film thickness in agreement with recent experiments. The temperature t* at which the superconductor to normal metal phase transition becomes of the first order is also analyzed.