Identification of intrinsic and extrinsic in-plane twofold symmetry in CsV3Sb5 via transport measurements

The identification of in-plane twofold symmetry in layered superconductors has sparked considerable interest. While transport measurements often reveal pronounced anisotropy, interpretation of their origin remains challenging due to the difficulty in disentangling competing contributions. Here, we systematically investigate the challenges of resolving intrinsic twofold symmetry in CsV3Sb5 through angular-dependent in-plane magnetoresistance measurements on exfoliated micron-scale devices. The sub-10−µm devices, with well-defined current directions, minimize contributions from structural domain walls and facilitate current-direction switching. Our experiments reveal a persistent twofold anisotropy in the upper critical field (Hc2), whose principal axis rotates with the applied current, indicating an extrinsic origin. The anisotropy also grows with increasing current, consistent with vortex motion driven by the Lorentz force. Two-axis rotational mapping combined with theoretical calculations further reveals how field misalignment can mimic or amplify apparent in-plane anisotropy. These results suggest that if intrinsic twofold symmetry does exist, its anisotropy is likely weak and highly susceptible to extrinsic influences. Our findings highlight the necessity of multiaxis and current-swapping methodologies for probing rotational symmetry in layered superconductors, and provide a refined framework for such investigations.