Investigation of in-plane anisotropy of c-axis magnetoresistance for BiCh 2 -based layered superconductor NdO 0.7 F 0.3 BiS 2

We investigated the in-plane anisotropy of the c -axis magnetoresistance (MR) in both superconducting and normal states of the single crystals of a BiCh 2 -based (Ch: chalcogen) superconductor NdO 0.7 F 0.3 BiS 2 . In the superconducting states of NdO 0.7 F 0.3 BiS 2 , four-fold-symmetric in-plane anisotropy of the c -axis MR was dominant below the superconducting transition temperature. Since the crystal structure of NdO 0.7 F 0.3 BiS 2 is tetragonal, the rotational symmetry in the superconducting state is preserved in the present compound. This result is clearly different from the cases in LaO 0.5 F 0.5 BiSSe 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 BiCh 2 -based system. The normal-state in-plane anisotropy was also investigated for NdO 0.7 F 0.3 BiS 2 .