Modulated reconstruction by epitaxial strain engineering and chemical arrangement in SrNbO₃ thin films

Correlated topological quantum materials hold great promise for next-generation quantum technologies, particularly in fault-tolerant quantum computing and energy-efficient spintronic devices, owing to the intricate interplay between strong electron correlations and topologically nontrivial band structures. To experimentally probe correlation-driven band reconstruction, perovskite oxide heterostructures provide an ideal platform, as their epitaxial films offer versatile degrees of freedom for physical modulation through strain or chemical control. In this work, we systematically fabricate high-quality SrNbO₃ thin films via pulsed laser epitaxy and investigate their electronic structures using angle-resolved photoemission spectroscopy (ARPES). Variation of the substrate oxygen stoichiometry drives a transition in the Fermi surface reconstruction from a $\sqrt{2}\times \sqrt{2}R{45}^{°}$ pattern on oxygen-deficient SrTiO₃ to a 2 × 2 pattern on stoichiometric substrates. Furthermore, by precisely controlling the epitaxial thickness, we identify the gradual disappearance of the electron-like Fermi surface at the M point with increasing thickness, which might be associated with the relaxation of the a⁰a⁰c⁺ lattice distortion induced by interfacial epitaxial strain at the SrTiO₃ substrate. Our findings demonstrate that band reconstruction in correlated oxides can be effectively modulated through chemistry and thin-film thickness, establishing SrNbO₃ as a promising material platform for multifunctional electronic band control. This work provides a prototypical route for exploring the intertwined topological and correlated phenomena in 4d transition-metal oxides under extreme quantum confinement.