Destruction of chain-superconductivity in YBa_2Cu_4O_8 in a weak magnetic field

TL;DR

This study investigates how a weak magnetic field affects chain-superconductivity in YBa_2Cu_4O_8 by measuring magnetic penetration depth anisotropy and its suppression, revealing insights into the superconducting mechanisms in this material.

Contribution

The paper provides new experimental data on the anisotropic magnetic penetration depth in YBa_2Cu_4O_8 and discusses the effects of weak magnetic fields on chain-superconductivity.

Findings

Downturn in penetration depth along b and c axes at low temperatures

Suppression of the downturn in the b-axis by ~0.25 T magnetic field

Evidence suggesting proximity-induced superconductivity in CuO chains

Abstract

We report measurements of the temperature dependent components of the magnetic penetration depth {\lambda}(T) in single crystal samples of YBa_2Cu_4O_8 using a radio frequency tunnel diode oscillator technique. We observe a downturn in {\lambda}(T) at low temperatures for currents flowing along the b and c axes but not along the a axis. The downturn in {\lambda}_b is suppressed by a small dc field of ~0.25 T. This and the zero field anisotropy of {\lambda}(T) likely result from proximity induced superconducting on the CuO chains, however we also discuss the possibility that a significant part of the anisotropy might originate from the CuO2 planes.