Spin-dependent size of interband hybridization gap: The interplay of adlayer and substrate states in Pb/Cu(111)

Abstract

An interband hybridization gap with spin-dependent size was detected in a low-dimensional electron system influenced by strong spin-orbit coupling. Energy gaps between hybridizing states are distinctly influenced by strong spin-orbit coupling. If the size of these gaps depends on the spin direction of the states, this may lead to fully spin-polarized valleylike structures. As a model system to study the hybridization mechanism behind such valleys, we investigate the unoccupied electronic band structure of Pb/Cu(111) by spin- and angle-resolved inverse photoemission in combination with first-principles calculations. Here, we find a hybridization gap with a splitting of about 200 meV for the one and even larger than 500 meV for the other spin direction. We develop an effective two-band tight-binding model and demonstrate that the interplay of adlayer and substrate states is crucial to induce a sizable spin-orbit coupling and hybridization strength to the interacting states.