s-wave pairing in the optimally doped LaO0.5F0.5BiS2 superconductor

We report on the magnetic and superconducting properties of LaO0.5F0.5BiS2 by means of zero-and transverse-field (ZF/TF) muon-spin spectroscopy measurements (mu SR). Contrary to previous results on iron-based superconductors, measurements in zero field demonstrate the absence of magnetically ordered phases. TF-mu SR data give access to the superfluid density, which shows a marked two-dimensional character with a dominant s-wave temperature behavior. The field dependence of the magnetic penetration depth confirms this finding and further suggests the presence of an anisotropic superconducting gap.