Manipulation of electronic structure via alteration of local orbital environment in [(SrIrO3)(m),(SrTiO3)](m=1, 2, and infinity) superlattices

Abstract

We investigated the electronic structure of [(SrIrO3)(m),(SrTiO3)](m = 1, 2, and infinity) superlattice (SL) thin films with optical spectroscopy and first principles calculations. Our optical results confirmed the existence of the J(eff) = 1/2 states in SL samples, similar to the bulk Ruddlesden-Popper series Sr Ir-n+ 1(n) O3n+1 iridates. Apart from this similarity, in the SL samples, we observed red shifts of the characteristic optical excitations in the J(eff) = 1/2 state and an enhancement of the low-energy spectral weight, which implies a reduction in the effective electron correlation for bands near the Fermi energy. The density functional theory plus Coulomb interactions (DFT + U) calculations suggested that the SrTiO3 layer intervened between SrIrO3 layers in the SLs activated additional hopping channels between the Ir ions, thus increasing the bandwidth and reducing the effective strength of the correlations. This paper demonstrates that fabrication of iridium-based heterostructures can be used to finely tune electronic structures via alteration of their local orbital environments.