Vortex lattice disorder in YBCO probed using Beta-NMR

TL;DR

This study uses Beta-NMR to investigate vortex lattice disorder near the surface of YBCO superconductors, revealing non-ideal vortex arrangements likely caused by pinning effects, with implications for understanding high-Tc superconductor behavior.

Contribution

It demonstrates the application of Beta-NMR to probe vortex lattice disorder in YBCO, highlighting the effects of pinning and surface inhomogeneities on vortex arrangements.

Findings

Vortex lattice disorder causes symmetric lineshape broadening.

Disorder effects are weakly dependent on applied magnetic field.

Vortex density varies across the sample face due to pinning.

Abstract

Beta-NMR has been used to study vortex lattice disorder near the surface of the high-Tc superconductor YBCO. The magnetic field distribution from the vortex lattice was detected by implanting a low energy beam of highly polarized 8Li into a thin overlayer of silver on optimally doped, twinned and detwinned YBCO samples. The resonance in Ag broadens significantly below the transition temperature Tc as expected from the emerging field lines of the vortex lattice in YBCO. However, the lineshape is more symmetric and the dependence on the applied magnetic field is much weaker than expected from an ideal vortex lattice, indicating that the vortex density varies across the face of the sample, likely due to pinning at twin boundaries. At low temperatures the broadening from such disorder does not scale with the superfluid density.