Nikl: časově-reverzní symetrii zachovávající partner železa v chalkogením topologickém izolantu

We report on the quenching of single Ni adatom moments on Te-terminated Bi2 Te2Se and Bi2Te3 topological insulator surfaces. The effect is noted as a missing x-ray magnetic circular dichroism for resonant L3,2 transitions into partially filled Ni 3d states of theory-derived occupancy nd = 9.2. On the basis of a comparative study of Ni and Fe using scanning tunneling microscopy and ab initio calculations, we are able to relate the element specific moment formation to a local Stoner criterion. Our theory shows that while Fe adatoms form large spin moments of ms = 2.54μB with out-of-plane anisotropy due to a sufficiently large density of states at the Fermi energy, Ni remains well below an effective Stoner threshold for local moment formation. With the Fermi level remaining in the bulk band gap after adatom deposition, nonmagnetic Ni and preferentially out-of-plane oriented magnetic Fe with similar structural properties on Bi2 Te2 Se surfaces constitute a perfect platform to study the off-on effects of time-reversal symmetry breaking on topological surface states.