On the Relationship Between the Critical Temperature and the London Penetration Depth in Layered Organic Superconductors

TL;DR

This paper analyzes measurements of the London penetration depth in layered organic superconductors, revealing significant discrepancies with BCS theory predictions and challenging existing theories of superconductivity in these materials.

Contribution

It provides a critical comparison between experimental data and theoretical models, highlighting the inadequacy of BCS theory and phase fluctuation models for these superconductors.

Findings

Discrepancy of up to two orders of magnitude with BCS predictions

Phase fluctuations do not determine the critical temperature

Kosterlitz--Thouless transition predictions are inconsistent with experiments

Abstract

We present an analysis of previously published measurements of the London penetration depth of layered organic superconductors. The predictions of the BCS theory of superconductivity are shown to disagree with the measured zero temperature, in plane, London penetration depth by up to two orders of magnitude. We find that fluctuations in the phase of the superconducting order parameter do not determine the superconducting critical temperature as the critical temperature predicted for a Kosterlitz--Thouless transition is more than an order of magnitude greater than is found experimentally for some materials. This places constraints on theories of superconductivity in these materials.