Yin-Yang vortex on UTe2 (011) surface

UTe2 is a candidate spin-triplet superconductor, yet its superconducting state remains debated. Using scanning tunneling microscopy/spectroscopy, we observe a novel magnetic vortex with distinct dark-bright contrast in local density of states on UTe2 (011) surface under perpendicular magnetic fields, resembling the Yin-Yang diagram in Taoism. Each vortex carries a quantized magnetic flux, and the boundary between the two parts aligns with crystallographic a-axis. The vortex states exhibit intriguing behaviors –– the Yang part exhibits a sharp zero-energy conductance peak, whereas the Yin part shows a superconducting gap with pronounced coherence peaks, sharper than those without fields. Theoretical analysis attributes this pattern to vortex-induced asymmetric suppression of topological surface states caused by the tilted Fermi surface, constraining possible d-vector orientations. Our findings constitute distinctive evidence for spin-triplet pairing in UTe2, and provide new avenues for exploring the interplay between surface states and vortex-bound states in topological superconductors. The authors discover a “Yin-Yang” vortex on the (011) surface of UTe2 under a perpendicular magnetic field by scanning tunneling microscopy/spectroscopy. Via theoretical modeling, they conclude that the observation of this vortex confirms the spin-triplet pairing of UTe2 and imposes constraints on the d-vector.