We performed angle-resolved photoemission spectroscopy (ARPES) experiments on an electron-doped ${\mathrm{Sr}}_2{\mathrm{RhO}}_4$ system ${\mathrm{Sr}}_{2-x}{\mathrm{Ce}}_x{\mathrm{RhO}}_4$ in order to investigate the electron doping-induced metal-insulator transition (MIT). We establish the universality of MIT in electron-doped ${\mathrm{Sr}}_2{\mathrm{RhO}}_4$ by comparing results from ${\mathrm{Sr}}_{2-x}{\mathrm{La}}_x{\mathrm{RhO}}_4$ and ${\mathrm{Sr}}_{2-x}{\mathrm{Ce}}_x{\mathrm{RhO}}_4$. Via a systematic analysis of doping-dependent transport and ARPES data, we show that the correlation driven MIT with a noninteger electron number in electron-doped ${\mathrm{Sr}}_2{\mathrm{RhO}}_4$ is universal and thus independent of the dopant. Within the universality, the ARPES analysis shows that the band topology determined by the spin-orbit coupling (SOC) is likely a control parameter of the insulating gap size and critical electron number of the MIT. We present a phase diagram of the insulating phase as a function of the effective SOC and electron number.

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• Electrical conductivity
• Luttinger's theorem
• Metal-insulator transition
• Phase diagrams
• Spin-orbit coupling
• Layered crystals
• Mott insulators
• Single crystal materials
• Angle-resolved photoemission spectroscopy
• Resistivity measurements
• Tight-binding model