Congrats to Gaurab Rimal and Tanzila Tasnim on their new paper out on the Kondo effect in SrIrO3 thin films in Physical Review Materials as a Letter! They’ve shown that epitaxial strain, in the form of different substrates, plays a key role in mediating a Kondo insulating state in SrIrO3. Tensile strain promotes the Kondo effect, while compressive strain suppresses it. This suggests that oxygen vacancies are the driver for the Kondo effect in these materials, since strain is known to correlate with vacancy formation in iridates (see https://doi.org/10.1103/PhysRevMaterials.8.055801). Thanks to Gabriel Calderon-Ortiz, Jinwoo Hwang, and George Sterbinsky for their contributions to the work using STEM and XAS to characterize the films.
The Kondo effect occurs when conduction electrons couple to magnetic impurity states in a material, which makes it most prominent in rare earth heavy fermion systems. Our result suggests that electron-doped SrIrO3 may resemble a heavy fermion system and have underlying magnetic behavior. We’ll have more to come in the future on this very interesting system!
Thanks to the U.S. Department of Energy Office of Science and the National Science Foundation (NSF) for funding this work! Also, a tip of the cap to Bharat Jalan’s group for showing us a new way to make SrIrO3 using a solid source metal-organic precursor and first showing that the Kondo effect is present in these ultra-pure films.