Enhancing Van‐Hove Singularities in SrRuO ₃ Films by Vacancy Engineering

Flat bands, characterized by their localized electronic states and van‐Hove singularities, provide an ideal platform for exploring many‐body physics. Herein, the origin of the existing nearly flat bands (NFBs) in SrRuO 3 thin films is investigated, and how to increase the number of them through structural modifications is demonstrated. Using a tight‐binding model that replicates experimental band structures, the SrRuO 3 monolayer is analyzed, revealing the origin of its NFBs along the x and y directions. These NFBs arise from destructive interference stabilizing strip‐type compact localized states. By introducing periodic Ru‐site vacancies, additional NFBs are generated, classified as partial or complete, depending on their Brillouin zone coverage. The compact localized states associated with these NFBs are identified, providing insight into their physical origin. For a 4‐layer SrRuO 3 multilayer film, many partial NFBs along the ΓX and XM directions are uncovered, and the distinct origin of their development is revealed. The findings highlight the potential of engineering flat bands in SrRuO 3 films, offering new opportunities for exploring correlated electronic phases and expanding the material platform for flat‐band physics.