Splitting a material in two creates new surfaces with under-coordinated or vacant surface sites. Examining associated changes in the electronic band structure — the electrons and their energy levels — reveals that destructive changes are also observed here; the band structure breaks down at the surface. Investigating surface band structures could help our understanding of heterogeneous catalysis, enabling both optimization and perhaps even the design of new processes.

They studied RbV3Sb5 single crystals kept and cleaved at 65 K in an ultrahigh vacuum chamber (10–11 mbar). In this environment, contaminants do not adsorb and occupy the vacant sites of the cleaved surface. To begin their studies, they analysed a freshly prepared surface with angle-resolved photo-emission spectroscopy (ARPES) to determine the electronic band structure of the starting material as a baseline, which matched literature values. Studying the spectra, Peng and co-workers were able to determine that cleaving the crystal led to Rb vacancies on the new surfaces, exposing the valence electrons of Sb to the vacuum. Next, they leaked in Xe at 10–9 mbar, which adsorbed onto the surface, before collecting a new ARPES spectra.