Synthesis and characterization of epitaxial Sr₂RhO₄ thin films

A 4d layered oxide, Sr2RhO4, has unquenched spin-orbit coupling resulting in intriguing collective modes such as spin-orbit excitons [1] despite its moderate spin-orbit coupling compared to 5d transition metal oxides. Recent studies on single crystals have shown that the metallic ground state of Sr2RhO4 is a confluence of the spin-orbit coupling, electron correlation, and structural distortion. In this presentation, we will discuss the synthesis and characterization of epitaxial Sr2RhO4 thin films. We have successfully deposited high-quality thin films on various oxide substrates using pulsed laser deposition. We have observed that Sr2RhO4 thin films are coherently strained and their optical spectra are overall consistent with that of single crystals. However, its resistivity has increased when they are under relatively large strain (> 1%), presumably due to weak localization. These epitaxial Sr2RhO4 thin films provide a tunable model system to explore the physics of moderate spin-orbit interaction and its competition with electron correlation in 4d transition metal oxides.