Paramagnetic Intrinsic Meissner Effect in Layered Superconductors

TL;DR

This paper predicts a paramagnetic intrinsic Meissner effect in layered superconductors caused by magnetic field-induced shrinking of Cooper pairs, differing from traditional models, and suggests experimental detection methods.

Contribution

It introduces a theoretical calculation showing a paramagnetic Meissner effect in layered superconductors at high fields, contrasting with existing models.

Findings

Discovery of a paramagnetic Meissner effect in layered superconductors.

Prediction of positive magnetic moment due to Cooper pair shrinking.

Proposals for experimental detection via torque and magnetization measurements.

Abstract

Free energy of a layered superconductor with $\xi_{\perp} < d$ is calculated in a parallel magnetic field by means of the Gor'kov equations, where $\xi_{\perp}$ is a coherence length perpendicular to the layers and $d$ is an inter-layer distance. The free energy is shown to differ from that in the textbook Lawrence-Doniach model at high fields, where the Meissner currents are found to create an unexpected positive magnetic moment due to shrinking of the Cooper pairs "sizes" by a magnetic field. This paramagnetic intrinsic Meissner effect in a bulk is suggested to detect by measuring in-plane torque, the upper critical field, and magnetization in layered organic and high-T$_c$ superconductors as well as in superconducting superlattices.