Topological Quantum Well States in Pb/Sb Thin-Film Heterostructures

Topological quantum well states in Pb/Sb thin-film heterostructures are investigated by angle-resolved photoemission spectroscopy and first-principles theoretical calculations. Emergent band dispersions are observed and explained in terms of propagation via coherent coupling between Sb topological surface states and Pb quantum well states. A superlattice approach is employed to accurately calculate the electronic band structures of Pb/Sb to account for sizeable lattice mismatch between Sb and Pb. The propagated Sb states are shown to possess highly delocalized wavefunctions and long coherence lengths, while retaining features corresponding to nontrivial band topology such as Dirac cone-like band dispersions and large in-plane spin polarization. Our results are relevant to the engineering of advanced spintronic devices and realization of exotic physical phenomena, including topological superconductivity, in composite thin‑film systems.