The discovery of conductivity and magnetism at the polar鈥搉onpolar interfaces of insulating nonmagnetic oxides such as 鈥婰aAlO3 and 鈥婼rTiO3 has raised prospects for attaining interfacial functionalities absent in the component materials. Yet, the microscopic origin of such emergent phenomena remains unclear, posing obstacles to design of improved functionalities. Here we present first principles calculations of electronic and defect properties of 鈥婰aAlO3/鈥婼rTiO3 interfaces and reveal a unifying mechanism for the origins of both conductivity and magnetism. We demonstrate that the polar discontinuity across the interface triggers thermodynamically the spontaneous formation of certain defects that in turn cancel the polar field induced by the polar discontinuity. The ionization of the spontaneously formed surface oxygen vacancy defects leads to interface conductivity, whereas the unionized Ti-on-Al antisite defects lead to interface magnetism. The proposed mechanism suggests practical design principles for inducing and controlling both conductivity and magnetism at general polar鈥搉onpolar interfaces.
L. Yu, A. Zunger,"" Nature Communications 5, 5118 (2014).(PDF)
