Ferroelectric field effect in ultrathin Sr₂IrO₄ films

Sr₂IrO₄ (SIO) is a J_eff = 1/2 Mott insulator with large spin-orbit coupling and strong correlation effect. The correlated behavior depends sensitively on the charge density. In this study, we investigate the effect of ferroelectric field effect doping in ultrathin SIO films. We deposit epitaxial PbZr_0.2Ti_0.8O₃ (PZT)/SIO heterostructures on LaAlO₃ (001) substrates via off-axis RF magnetron sputtering, with atomically smooth surface and high crystallinity achieved. By switching the polarization of PZT, we demonstrate nonvolatile resistance switching in 2-3 nm SIO channels. The field effect modulation increases with decreasing channel thickness and temperature. In PZT/2.6 nm SIO, the resistance switching ratio between the polarization up and down states of PZT is ~5% at room temperature, which increases to ~10% at 10 K. We compare the results with the field effect obtained on SrIrO₃ channels with similar thickness and discuss the critical material parameters that control the magnitude of the modulation.