S-wave pairing in the optimally doped LaO_0.5F _0.5BiS₂ superconductor

We report on the magnetic and superconducting properties of LaO _0.5F_0.5BiS₂ by means of zero- and transverse-field (ZF/TF) muon-spin spectroscopy measurements (μSR). Contrary to previous results on iron-based superconductors, measurements in zero field demonstrate the absence of magnetically ordered phases. TF-μSR 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.