An energy-dependent broadening of Rashba-like spin splitting in Au2Sb surface alloy with periodic structural defect
Here, we report a novel AuSb 2D superstructure on Au(111) that shows agreements and discrepancies to the expected electronic features of the ideal 2D surface alloys with $\sqrt{3}\times\sqrt{3}$ periodicity. Using spin- and angle-resolved photoemission spectroscopy, we find a spin splitting of the alloy bands with antiparallel spin polarization, stemming from Rashba spin-orbit coupling. However, the observed Rashba bands are significantly broadened. Taking advantage of the good agreement between the experimental results and DFT calculations, we determine that the broadening of the Rashba band is due to the perturbations from the 3-pointed-star-shaped defects acting as nonresonant impurities in the Au2Sb superstructure. These periodic defects can shift the energy position of the Rashba band without breaking the in-plane rotational symmetry and mirror symmetry, which suggests that introducing periodic defects into a Rashba SOC system possesses a great potential in engineering the spin-dependent properties of spintronic devices.