Universality of charge doping driven metal-insulator transition in Sr2RhO4 and role of spin-orbit coupling

Abstract

We performed angle-resolved photoemission spectroscopy (ARPES) experiments on an electron-doped ${\mathrm{Sr}}_{2}{\mathrm{RhO}}_{4}$ system ${\mathrm{Sr}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{RhO}}_{4}$ 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 ${\mathrm{Sr}}_{2\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{RhO}}_{4}$ and ${\mathrm{Sr}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{RhO}}_{4}$. 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.