Study of the magnetic penetration depth in RbOs_2O_6

TL;DR

This study investigates the magnetic penetration depth in the superconductor RbOs_2O_6 using muon-spin-rotation, confirming weak-coupled s-wave BCS behavior and an isotropic energy gap at low temperatures.

Contribution

The paper provides the first muon-spin-rotation measurements of bb in RbOs_2O_6, demonstrating its isotropic superconducting gap and field-independent penetration depth.

Findings

bb saturates below 0.2T_c, consistent with BCS theory

bb at T=0 is 250-300 nm

Penetration depth is nearly field-independent at low temperatures

Abstract

Measurements of the magnetic field penetration depth \lambda in the pyrochlore superconductor RbOs_2O_6 (T_c\simeq6.3 K) were carried out by means of the muon-spin-rotation (\muSR) technique. At low temperatures \lambda^{-2}(T) saturates and becomes constant below T\simeq 0.2T_c, in agreement with what is expected for weak-coupled s-wave BCS superconductors. The value of \lambda at T=0 was found to be in the range of 250 nm to 300 nm. \muSR and equilibrium magnetization measurements both reveal that at low temperatures $\lambda$ is almost (at the level of 10%) independent of the applied magnetic field. This result suggests that the superconducting energy gap in RbOs_2O_6 is isotropic.