Peak effect in a superconductor/normal metal strip being in vortex-free state

TL;DR

This paper predicts a novel peak effect in the critical current and magnetization of superconductor/normal-metal strips occurring at low fields in the vortex-free phase, due to unique current-supervelocity relations.

Contribution

It introduces the theoretical prediction of a peak effect in vortex-free superconductor/normal-metal hybrids, linked to specific current-supervelocity characteristics.

Findings

Peak effect occurs at low magnetic fields in vortex-free phase.

Effect is related to the structure's current-supervelocity relation with two maxima.

Potential existence of similar effects in two-band superconductors like MgB₂.

Abstract

We theoretically predict that the critical current $I_c$ and magnetization $M$ of hybrid superconductor/normal-metal (SN) strip may have nonmonotonous dependence on perpendicular magnetic field - so called peak effect. In contrast to familiar peak effect, which is connected either with vortex entry to the superconductor or with peculiarities of vortex pinning, the found phenomenon exists at low fields, in the vortex-free (Meissner) phase. We argue that the effect appears at specific parameters of studied hybrid structure when its in-plane current-supervelocity relation has two maxima. We expect that the same peak effect may exist in two-band superconductors (like MgB$_2$) where similar current-supervelocity dependence was predicted at low temperatures.