Dial It Down: The Effect of Strongly Interacting Adsorbates on the BiAg₂Rashba Surface State

Organic semiconductors interfaced with spin–orbit coupled materials offer a rich playground for fundamental studies of controlling spin dynamics in spintronic devices. The adsorbate–surface interactions at such interfaces play a key role in determining the valence electronic and spin structure and consequently, the device physics as well. Here we show that strong adsorbate–surface alloy interaction leads to weakening of the electronic coupling between the surface alloy atoms and quenches the spin–orbit coupled surface state, demonstrated for the case of the strong organic electron acceptor 2,7-dinitropyrene-4,5,9,10-tetrone (NO₂–PyT, C₁₆H₄N₂O₈) on the Rashba spin–orbit coupled surface alloy BiAg₂/Ag(111). Our findings demonstrate an important challenge associated with using molecular adsorbates to tailor the spin texture in BiAg₂/Ag(111), and our work provides guidelines to consider while designing interfacial systems to engineer the spin texture in Rashba surface alloys.