Angle-Resolved Photoemission Spectroscopy of Cubic Perovskite BaRuO₃ Thin Films Grown by Molecular-Beam Epitaxy

Perovskite ruthenates such as SrRuO₃ and CaRuO₃ have been studied extensively for their exciting electronic and magnetic properties and have provided great platforms to study correlated electron systems. The cubic perovskite (3C) BaRuO₃ could also provide insight into such systems, especially with its simpler electronic structure when compared to those of orthorhombic SrRuO₃ and CaRuO₃. Nonetheless, 3C BaRuO₃ has been far less explored due to the necessity of high pressure to synthesize it in bulk and competition during growth from other polymorphs (4H, 6H, and 9R). Here we use a combination of ozone-assisted molecular-beam epitaxy (MBE) and in situ angle-resolved photoemission spectroscopy (ARPES) to study the electronic and magnetic properties of 3C BaRuO₃. We demonstrate an adsorption-controlled growth regime that allows for the growth of commensurately-strained films with enhanced residual resistivity ratios compared to previously reported thin films grown by pulsed-laser deposition. First-ever ARPES measurements on these 3C BaRuO₃ thin films reveal saddle points in close proximity to the Fermi level. A detailed accounting of the fermiology, quasiparticle characteristics, and possible signatures of magnetic ordering as a function of thickness and temperature will be discussed.