Substrate-tuning of correlated spin-orbit oxides revealed by optical conductivity calculations.

Bongjae Kim,Kyoo Kim,Beom Hyun Kim,B I Min

doi:10.1038/srep27095

Abstract

We have systematically investigated substrate-strain effects on the electronic structures of two representative Sr-iridates, a correlated-insulator Sr2IrO4 and a metal SrIrO3. Optical conductivities obtained by the ab initio electronic structure calculations reveal that the tensile strain shifts the optical peak positions to higher energy side with altered intensities, suggesting the enhancement of the electronic correlation and spin-orbit coupling (SOC) strength in Sr-iridates. The response of the electronic structure upon tensile strain is found to be highly correlated with the direction of magnetic moment, the octahedral connectivity, and the SOC strength, which cooperatively determine the robustness of Jeff = 1/2 ground states. Optical responses are analyzed also with microscopic model calculation and compared with corresponding experiments. In the case of SrIrO3, the evolution of the electronic structure near the Fermi level shows high tunability of hole bands, as suggested by previous experiments.

Highlights

We have systematically investigated substrate-strain effects on the electronic structures of two representative Sr-iridates, a correlated-insulator Sr2IrO4 and a metal SrIrO3
Due to the prominent role of large spin-orbit coupling (SOC) of Ir 5d electrons, which is comparable to the strengths of Coulomb correlation (U) and bandwidth (W), intensive attention has been focused on the Sr-iridates of Ruddlesden-Popper type, Srn+1IrnO3n+1
This feature was explained by the enhancements of both U and W, which increase the separation of upper Hubbard band (UHB) and lower Hubbard band (LHB) and makes both bands more dispersive, respectively

Summary

Introduction

We have systematically investigated substrate-strain effects on the electronic structures of two representative Sr-iridates, a correlated-insulator Sr2IrO4 and a metal SrIrO3. Sr2IrO4 (214) with n = 1 and SrIrO3 (113) with n =∞are representative systems, which correspond to the insulating and metallic limits, respectively Both systems have been described based on the Jeff = 1/2 ground states, where the former has a well-separated Mott-gap, while the latter is thought to be a correlated metal[3,4,5]. Optical experiments for aforementioned Sr-iridates, which act as a direct probe of electronic structures, show two-peak structure near the Mott gap region (see Fig. 1(a,c)) Cluster-based microscopic model calculations are employed to do parameter-wise analysis of optical www.nature.com/scientificreports/

Methods

Results

Conclusion