Magnetic breakdown in a normal-metal - superconductor proximity sandwich

TL;DR

This paper investigates the magnetic behavior of a normal-metal layer in contact with a superconductor, revealing bistability and a first-order transition at a breakdown field, with theoretical results compared to experiments.

Contribution

It provides a detailed theoretical analysis of magnetic breakdown phenomena in normal-metal superconductor proximity systems, including phase transitions and experimental validation.

Findings

Identification of two stable magnetic states in the system.

Characterization of the first-order transition and its critical parameters.

Experimental comparison confirming theoretical predictions.

Abstract

We study the magnetic response of a clean normal-metal slab of finite thickness in proximity with a bulk superconductor. We determine its free energy and identify two (meta-)stable states, a diamagnetic one where the applied field is effectively screened, and a second state, where the field penetrates the normal-metal layer. We present a complete characterization of the first order transition between the two states which occurs at the breakdown field, including its spinodals, the jump in the magnetization, and the latent heat. The bistable regime terminates at a critical temperature above which the sharp transition is replaced by a continuous cross-over. We compare the theory with experiments on normal-superconducting cylinders.