Lifshitz-transition-driven metal-insulator transition in moderately spin-orbit-coupled Sr2-xLaxRhO4

Abstract

© 2019 American Physical Society.Motivated by the novel insulating state of Sr2IrO4 from strong spin-orbit coupling (SOC), we investigate, by means of angle resolved photoemission, the metal-insulator transition (MIT) mechanism in Sr2-xLaxRhO4 whose mother compound is isovalent and isostructural but has smaller SOC strength compared to Sr2IrO4. Transport and angle resolved photoemission results from single crystalline Sr2-xLaxRhO4 revealed that the MIT occurs coincidentally with a multi-to single-band transition (Lifshitz transition) at x=0.4. Starting from x=0.4, there is a gradual but anomalous enhancement in the band gap size with additional electron doping, suggesting that the insulating phase in Sr2-xLaxRhO4 is a new type which has been rarely investigated. These results suggest that the insulating phase in Sr2-xLaxRhO4 is likely induced by the moderate SOC strength and electron doping effect from the La. Our findings not only elucidate the MIT mechanism in Sr2-xLaxRhO4, but may also open new avenues for novel MIT research in moderate SOC regimes