Driven vortices in type-II superconductors: A muon spin rotation study

Abstract

We present a detailed study of vortex motion in a type-II superconductor using the muon spin rotation $(\ensuremath{\mu}\mathrm{SR})$ technique. The vortices were set in motion by an alternating transport current. By adjusting the frequency and amplitude of the driving force so that vortices ``visible'' to the implanted muons did not cross the sample boundaries, a $\ensuremath{\mu}\mathrm{SR}$ line shape was obtained corresponding to almost perfectly ordered vortex motion. We also observed sidebands to the $\ensuremath{\mu}\mathrm{SR}$ line shape which correspond to the frequency at which vortices pass the implanted muon, and allow a direct measurement of the vortex velocity. Both these features of the line shape confirm numerical predictions reported in a previous study [see Charalambous et al., Phys. Rev. B 66, 054506 (2002)].