Possible Anisotropic Order Parameter in Pyrochlore Superconductor KOs$_2$O$_6$ Probed by Muon Spin Rotation

TL;DR

This study investigates the magnetic penetration depth in the pyrochlore superconductor KOs$_2$O$_6$ using muon spin rotation, revealing anisotropic superconducting order parameter characteristics through deviations from expected models.

Contribution

The paper provides experimental evidence of anisotropic order parameter in KOs$_2$O$_6$ via muon spin rotation measurements, highlighting deviations from conventional models.

Findings

Temperature dependence of penetration depth deviates from two-fluid model

Penetration depth increases with applied magnetic field

Evidence suggests anisotropic superconducting order parameter

Abstract

Magnetic penetration depth ($\lambda$) in a pyrochlore superconductor KOs$_2$O$_6$ was studied by means of muon spin rotation (\msr). The temperature dependence of transverse spin relaxation rate, which is proportional to $\lambda ^{-2}$, exhibits a considerable deviation from that expected for the empirical two-fluid model ($\propto T^4$), rather obeying a $T^2$-tendency. Furthermore, $\lambda$ apparently increases with increasing applied field, suggesting the presence of nonlinear and nonlocal effects. These findings strongly suggest that the superconducting order parameter in KOs$_2$O$_6$ is anisotropic.