Alkali-metal induced electronic structure evolution in Sn4Sb3 studied by angle-resolved photoemission spectroscopy

Abstract

We report on an angle-resolved photoemission spectroscopy study of the effect of in-situ cesium (Cs) dosing on the surface electronic structure of Sn4Sb3, a newly emerging candidate of topological semimetallic superconductor. As the chemical potential of the system increases upon Cs dosing, we observed an electronic structure evolution that features an increasing sharpness of band features as well as a momentum- and band-dependent energy shift of the bands at low binding energies. These observations go beyond a simple rigid band shift model and are manifestations of quantum confinement of electronic states near the surface due to Cs decoration. By studying the evolution of Cs 5p core level as functions of Cs dosage and photoelectron emission angle, we found Cs atoms deposit on the sample surface at low dosages and tend to intercalate underneath the surface at high dosages. This process is accompanied by a gradual suppression of a surface band splitting, an observation that can be captured by simplified first-principles calculations in both cases with the deposition/intercalation occurring on top of/underneath the first Sn–Sb bilayer. Our finding highlights an intriguing possibility of an unexpected dimensionality reduction in Sn4Sb3 caused by Cs intercalation at interstitial sites that promises its novel surface properties different from the bulk.