Ferroelectric Polarization Induced Metal-Insulator Transition in Epitaxial Sr₃Ir₂O₇ Films

We report the study of the ferroelectric field effect in ultrathin 5d iridate Sr₃Ir₂O₇ (SIO327) films. We deposit epitaxial heterostructures PbZr_0.2Ti_0.8O₃ (PZT)/SIO327 (2.1- 4.2 nm) on LSAT (001) substrates via off-axis RF magnetron sputtering. The heterostructures have atomically smooth surfaces and high crystallinity. By switching the polarization of PZT, we demonstrate nonvolatile resistance modulation of the SIO327 channels. The 4.2 nm thick channel exhibits metallic behavior at high temperature followed by insulating behavior below T_MI ~220 K in the P_down state. In the P_up state, T_MI decreases to 150 K. The resistance switching ratio ΔR/R_up is ~5% at 300 K and increases to ~20% at 2 K. Larger resistance modulation has been observed in thinner channels. We extract the carrier density and mobility by combining the Hall effect measurements with the magnetoresistance at both polarization states, and discuss the effects of carrier density and spin-orbit coupling on the transport properties of SIO327.