Tuning the Dimensionality of Materials with Strongly Correlated Electrons between 1D and 2D*

Tuning the dimensionality of a system offers a useful tool for realizing new quantum phenomena associated with critical phase transitions and topological properties. However, only a few naturally occurring materials with tunable, intrinsic 1D and 2D structures are available for experimental studies. In this talk, I will present a new approach of synthesizing 1D – 2D quantum systems by creating dimensionally-confined stripe-superlattices from in-plane oriented layered materials. For example, we have demonstrated this method to synthesize 1D – 2D IrO₂ stripes using a-axis oriented superlattices of Sr₂IrO₄ and insulating (La,Sr)GaO₄, both are of the K₂NiF₄ symmetry [1]. The dimensional confinement of the superlattices has been confirmed by structural characterizations. Optical spectroscopy shows clear anisotropic characteristics and dimensional electronic confinement of the spin-orbit coupled J_eff = 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 tuning the dimensionality between 1D and 2D via stripe-superlattices is a viable technique for obtaining dimensionality-induced quantum phase transitions in materials with strongly correlated electrons.

[1] J. H. Gruenewald et al., Adv. Mater. 29, 163798 (2017).