A. Seo - Tuning the Dimensionality of Strongly Correlated Materials down to 1D

Speaker: A. Seo, University of Kentucky

Abstract: One-dimensional (1D) systems offer a useful platform for studying low-dimensional phenomena often associated with the onset of critical quantum phase transitions. While exactly solvable models, such as Luttinger liquid theory, are thought to describe 1D systems very well, only a few naturally occurring materials with intrinsic 1D structure are available for experimental studies. In this colloquium, I will present a new approach of synthesizing 1D quantum systems by creating dimensionally-confined stripe-superlattices from in-plane oriented 2D layered oxides. We have used this method to synthesize 1D IrO₂ stripes using a-axis oriented superlattices of Sr₂IrO₄ and insulating (La,Sr)GaO₄, both are of the K₂NiF₄ symmetry. The dimensional confinement of our 1D superlattices has been confirmed by structural characterizations. Optical spectroscopy shows clear anisotropic characteristics and one-dimensional electronic confinement of the spin-orbit split Jeff = 1/2 band. Spin and orbital excitations observed in resonant inelastic x-ray scattering spectra suggest larger exchange interactions and more confined orbital excitations in the 1D IrO₂ stripes as compared to its 2D counterpart. The observed electronic confinement and localized spin-structure are quite consistent with density functional theory calculations. This method of transforming layered materials into 1D striped structures is a viable technique for obtaining dimensional-crossover phase transitions while tuning from two- to one-dimension.