Electrical control of phase transitions through ion transfer in oxide superlattices

Electrical control of phase transitions through ion transfer has been of great interest recently. Ion transfer can have a dramatic influence on a material’s electronic, magnetic and optical properties, and thereby provides a powerful tool for fundamental research and enables many practical applications. However only a few materials have been found to exhibit significant tunability and good reversibility of electrically controlled ion transfer. In this talk, we show that superlattices comprised of the 5d oxide SrIrO₃ and 3d oxide La_1-xSr_xMnO₃ exhibit a reversible phase change under ionic liquid gating. Ionic liquid gating modulates the lattice constant by seven percent and modifies the valence of both Mn and Ir cations. The gate voltage induces a reversible transition between a ferromagnetic metallic state and a nonmagnetic insulating state, along with a large modulation of optical transmittance. Secondary ion mass spectrometry indicates that these reversible transitions are mediated by the transfer of hydrogen and oxygen ions in the superlattices. Single layer films of the constituent materials do not exhibit such significant changes in properties. Our study shows that the electrically controlled ion transfer can be engineered by designing materials at the atomic scale.