Modulation of the Metal-Nonmetal Crossover in SrIrO3/CaMnO3 Superlattices

Due to a combination of the interplay between electron- electron correlation (EEC) and spin-orbit coupling, 3d-5d transition-metal oxide interfaces have been an intriguing platform for the exploration of emergent quantum phenomena. In this work, we investigate the 3d-5d electron coupling by designing SrIrO3/CaMnO3 superlattices and studying their electrical transport behaviors. The [(SrIrO3)(n)/(CaMnO3)(n)](m) super-lattices show a metal-nonmetal crossover (MNC) with the critical temperature increasing monotonically with decreasing n, until n = 1, a nonmetallic behavior is observed up to room temperature. Detailed analyses reveal that the MNC is the consequence of the weak localization modified by the enhanced EEC in SrIrO3 competing with the effective field of spin- orbital relaxation, with the interfaces with CaMnO3 being introduced to the superlattices. This study provides a framework for understanding the microscopic picture of 3d-5d electron coupling.