Enhanced orbital anisotropy through the proximity to a SrTiO3 layer in the perovskite iridate superlattices

DOI number:10.1103/PhysRevB.104.075156

Journal:Physical Review B

Key Words:OXIDE；HETEROSTRUCTURES；PHYSICS

Abstract:We have used angle-dependent soft x-ray absorption spectroscopy (XAS) at the O K edge and first-principles calculations to investigate the electronic structures of iridate-based superlattices (SrIrO3)(m)/(SrTiO3) (m = 1, 2, 3, and infinity). We focus on the pre-edge Ir 5d t(2g)-O 2p orbital hybridization feature in the XAS spectra. By varying the measurement geometry relative to the incident photon polarization, we are able to extract the dichroic contrast and observe the systematic increase in the anisotropy of Ir 5d orbitals as m decreases. First-principles calculations elucidate the orbital anisotropy coming mainly from the enhanced out-of-plane compression of IrO6 octahedra in the SrIrO3 layers that are adjacent to the inserted SrTiO3 layers. As m decreases, the increased volume fraction of these interfacial SrIrO3 layers and their contact with the SrTiO3 layers within the (SrIrO3)(m)/(SrTiO3) supercell lead to enhanced orbital anisotropy. Furthermore, the tilt and rotation of IrO6 octahedra are shown to be essential to understand the subtle orbital anisotropy in these superlattices, and constraining these degrees of freedom will give an incorrect trend. Our results demonstrate that the structural constraint from the inserted SrTiO3 layers, in addition to other electronic means such as polar interface and charge transfer, can serve as a knob to control the orbital degree of freedom in these iridate-based superlattices.

Co-author:Wanling Liu,Yu-Cheng Shao, Xuefei Feng, Nian Zhang, Jiamin Fu, Jenn-Min Lee, Dawei Shen, Yi-De Chuang,Xiaosong Liu

First Author:Wencheng Huang

Correspondence Author:Wencheng Huang

Document Code:075156

Volume:104

Issue:7

ISSN No.:2469-9950

Translation or Not:no

Date of Publication:2021-08-30

Links to published journals:https://journals.aps.org/prb/abstract/10.1103/PhysRevB.104.075156