Microscopic properties of vortex state in YB6 probed by muon spin rotation

TL;DR

This study investigates the microscopic vortex properties of YB6 superconductor using muon spin rotation, revealing conventional s-wave pairing and emphasizing the importance of the Ginzburg-Landau model near vortex cores.

Contribution

It provides a detailed comparison of the modified London and Ginzburg-Landau models for muSR data, highlighting the latter's accuracy at higher fields in YB6.

Findings

Ginzburg-Landau model better fits muSR data at high fields

No evidence of nonlocal effects or low-lying quasiparticles in $\\lambda$

Superconductivity in YB6 is conventional s-wave with isotropic pairing

Abstract

Local magnetic field distribution B(r) in the mixed state of a boride superconductor, YB6, is studied by muon spin rotation (muSR). A comparative analysis using the modified London model and Ginzburg-Landau (GL) model indicates that the GL model exhibits better agreement with muSR data at higher fields, thereby demonstrating the importance of reproducing the field profile near the vortex cores when the intervortex distance becomes closer to the GL coherence length. The temperature and field dependence of magnetic penetration depth ($\lambda$) does not show any hint of nonlocal effect nor of low-lying quasiparticle excitation. This suggests that the strong coupling of electrons to the rattling motion of Y ions in the boron cage suggested by bulk measurements gives rise to a conventional superconductivity with isotropic s-wave pairing. Taking account of the present result, a review is provided for probing the anisotropy of superconducting order parameters by the slope of $\lambda$ against field.