Comment on "Orbital Paramagnetism of Electrons in Proximity to a Superconductor"

TL;DR

This paper critically examines previous claims of a significant paramagnetic reentrance effect in proximity-coupled superconducting cylinders, showing that the calculated effect is much smaller than observed experimentally.

Contribution

It provides a detailed critique demonstrating that the theoretical calculations significantly underestimate the experimentally observed paramagnetic reentrance.

Findings

Calculated paramagnetic susceptibility is several orders of magnitude smaller than experimental values.

Challenges the interpretation of the reentrance effect as a simple proximity-induced paramagnetism.

Highlights the need for alternative explanations for the observed phenomena.

Abstract

In a recent letter [Phys. Rev. Lett. 80, 5782 (1998)], Bruder and Imry address the reentrance effect in proximity coupled normal-metal coated superconducting cylinders discovered by Mota et al. and challenging theoretical understanding to date. At stake is the explanation of a low-temperature paramagnetic reentrance of order unity. The authors claim to find a `significant paramagnetic effect' which they strongly relate to the layout and findings of the experiment. Here, we show that the straightforward calculation of the paramagnetic change in the susceptibility along the lines of their analysis is by several orders of magnitude smaller than experimentally observed.