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Tuning the electronic structure of layered perovskites is a powerful pathway to control their properties for future applications. The electronic structure of Sr$_2$RuO$_4$ can be controlled by small structural distortions, with in-plane rotations of the oxygen octahedra moving the van Hove singularity across the Fermi level. This Lifshitz transition is expected to result in significant consequences for the ground state and the properties of the superconductivity [1-2]. Here, we study the effect of chemical pressure by substitution with isovalent Ba atoms in Sr$_{2−𝑥}$Ba$_𝑥$RuO$_4$ for 𝑥 = 0, 0.2, and 0.4 by Scanning Tunnelling Microscopy (STM). We report a systematic study of the structural and electronic changes with substitution level. Despite the substitution being isoelectronic and away from the electronically active RuO$_2$ plane, our results show substantial inhomogeneity of the electronic structure close to the Fermi energy. Our results highlight the connection between electronic and lattice degrees of freedom and demonstrate control of the electronic structure.
[1] Marques, C. A. et al. Advanced Materials 33, 2100593 (2021).
[2] Profe, J. B. et al. Phys. Rev. Research 6, 043057 (2024).