Hierarchy of Lifshitz Transitions in the Surface Electronic Structure of Sr₂RuO₄ under Uniaxial Compression

We report the evolution of the electronic structure at the surface of the layered perovskite Sr₂RuO₄ under large in-plane uniaxial compression, leading to anisotropic B_1g strains of ε_xx − ε_yy = −0.9±0.1%. From angle-resolved photoemission, we show how this drives a sequence of Lifshitz transitions, reshaping the low-energy electronic structure and the rich spectrum of van Hove singularities that the surface layer of Sr₂RuO₄ hosts. From comparison to tight-binding modeling, we find that the strain is accommodated predominantly by bond-length changes rather than modifications of octahedral tilt and rotation angles. Our study sheds new light on the nature of structural distortions at oxide surfaces, and how targeted control of these can be used to tune density of state singularities to the Fermi level, in turn paving the way to the possible realization of rich collective states at the Sr₂RuO₄ surface.