c-axis penetration depth of Hg-1201 single crystals

TL;DR

This study directly measures the c-axis penetration depth in Hg-1201 single crystals, revealing it is much longer than theoretical predictions, which challenges existing models of superconductivity in layered cuprates.

Contribution

The paper provides the first direct imaging-based measurement of the c-axis penetration depth in Hg-1201, showing significant discrepancies with the interlayer tunneling model.

Findings

Measured c-axis penetration depth is about 10 microns.

The observed length is 10 times longer than theoretical predictions.

Results suggest the interlayer tunneling mechanism contributes less to superconductivity than previously thought.

Abstract

We have magnetically imaged interlayer Josephson vortices emerging from an ac face of single crystals of the single layer cuprate high-Tc superconductor (Hg,Cu)Ba2CuO4+d. These images provide a direct measurement of the c-axis penetration depth of about 10 microns. This length is a factor of 10 longer than predicted by the interlayer tunneling model for the mechanism of superconductivity in layered compounds, indicating that the condensation energy available through this mechanism is 100 times smaller than is required for superconductivity.