The study examines the surface and bulk electronic states of a single-crystal thallium film, a heavy metal that has been little explored in this regime of structural order. Distinguishing between surface and bulk contributions is key to correctly interpreting the electronic properties of thin films, where broken symmetry and interface effects can dominate the measured response.

Thallium is a boron-group element with a hexagonal close-packed crystal structure and strong spin-orbit coupling, making it an interesting candidate for studying electronic states with topological character or strong spin mixing. Realizing single-crystal films makes it possible to address these questions with a structural quality that polycrystalline samples cannot offer.

The combination of surface and bulk measurements on the same single-crystal sample is the methodological centerpiece of the work, allowing contributions that usually appear mixed in conventional experiments to be separated. Such separation is necessary to compare the results with electronic structure calculations and with models of surface states.

The results provide a characterization of the electronic states of thallium in single-crystal film form that will serve as a reference for future studies of heavy metals with strong spin-orbit coupling and for the design of heterostructures exploiting surface states in chemically similar systems.