Spin-orbit coupling (SOC) is a key ingredient of nontrivial band topology in weakly interacting materials. On the other hand, the impact of SOC in strongly correlated systems often manifests in magnetic anisotropy. 5d transition metal oxides offers unique opportunities to explore the SOC-correlation interplay since they have a similar energy scale. A prominent example is the square-lattice iridates which are surprisingly similar to weakly spin-orbit-coupled high-Tc cuprates. To understand this intriguing SOC-correlation interplay, it is necessary to obtain toy-model systems where the interactions can be experimentally tuned by structural engineering of dimensionality, strain, lattice distortion, etc. In this talk, I will discuss our recent work on pseudospin-half square lattices realized in artificial perovskite superlattices as well as the Ruddlesden-Popper phases. Our goal is to enforce various symmetry configurations to controllably enable different emergent behaviors. This allows us to demonstrate control of the antiferromagnetic fluctuations in virtual of the hidden SU(2) symmetry of artificial perovskite superlattices and archive giant magnetic responses probed by resonant x-ray scattering. Signatures of the Slater-Mott crossover regime was also identified. Anisotropic strains of orthogonal symmetry channels were applied to the Ruddlesden-Popper phase to realize metamagnetic switching and induce a rare quartic anisotropy for spatial spin modulation. The results showcase the rich emergent behaviors and functional properties beyond the analogy with cuprates.
Jian Liu obtained his Ph.D. in 2012 from the University of Arkansas and was a doctoral fellow of the Advanced Light Source. After that, he became a postdoctoral fellow at the University of California – Berkeley from 2012 to 2015, and became an Assistant Professor in 2015 and an Associate Professor in 2021 at the University of Tennessee. He is a recipient of the CAREER award by the National Science foundation, the Young Investigator Program award by the Office of Naval Research, and the Visiting Scientist Award by the Advanced Photon Source.