Anomaly in YBa2Cu4O8 charge distribution below Tc: a zero-field muSR study

TL;DR

This study uses zero-field muon spin relaxation to detect changes in charge distribution in YBa2Cu4O8 below its critical temperature, indicating an anomaly associated with superconductivity.

Contribution

It provides evidence of a charge distribution change in YBa2Cu4O8 below T_c using muSR, suggesting a link between charge dynamics and superconductivity.

Findings

Enhanced muSR relaxation rate below T_c

Relaxation driven by nuclear dipole interaction at all temperatures

Charge distribution modification possibly causes relaxation increase

Abstract

Zero-field $\mu$SR measurements in $^{63}$Cu isotope enriched and natural YBa$_2$Cu$_4$O$_8$ powders are presented. The temperature dependence of the $\mu^+$ relaxation rate is characterized by a sizeable enhancement below T$_c$. The comparison of the asymmetry decay in the two samples reveals that the $\mu^+$ relaxation is driven by nuclear dipole interaction from 300 K down to 4.2 K. It is argued that the increase in the relaxation below T$_c$ originates from a change in $\mu^+$ site, possibly due to a modification in the charge distribution within CuO chains.