Exploration of the bond angle and charge carrier density by rare-earth doping in Sr2IrO4

Doping at the Sr site in ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$ is predicted to be a possible route to high-temperature superconductivity, which has not yet been experimentally achieved. We have made a comprehensive investigation on the interplay among the Ir-O-Ir bond angle, carrier density, and magnetic and transport properties of rare-earth-doped ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$ by choosing Pr and Ce as the dopants. We find that compared with Pr doping, Ce doping introduces more effective charge carriers into the ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$ matrix, leading to a more rapid suppression of its magnetic ordering. A metallic-like behavior has been observed in heavily Ce-doped samples. The evolutions of magnetic and transport behaviors are found to be less relevant to the distorted Ir-O-Ir bond angle. The present results suggest that the charge carrier density could be a crucial factor in determining the physical properties of rare-earth-doped ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$ compounds.