Investigation of in-plane anisotropy of c-axis magnetoresistance for BiCh2-based layered superconductor NdO0.7F0.3BiS2

We investigated the in-plane anisotropy of the c-axis magnetoresistance (MR) in both superconducting and normal states of the single crystals of a BiCh2-based (Ch: chalcogen) superconductor NdO0.7F0.3BiS2. In the superconducting states of NdO0.7F0.3BiS2, four-fold-symmetric in-plane anisotropy of the c-axis MR was dominant below the superconducting transition temperature. Since the crystal structure of NdO0.7F0.3BiS2 is tetragonal, the rotational symmetry in the superconducting state is preserved in the present compound. This result is clearly different from the cases in LaO0.5F0.5BiSSe single crystals, where the in-plane MR in the superconducting state showed clear two-fold symmetry such as nematic superconductivity. These differences between four-fold and two-fold symmetry in superconducting states could be attributed to constituent elements in the conducting layer (with or without Se). Therefore, the present results propose that switching from nematic to non-nematic superconductivity states could be achieved in the BiCh2-based system. The normal-state in-plane anisotropy was also investigated for NdO0.7F0.3BiS2.