Charge Transfer in Iridate-Manganite Superlattices

Abstract

Charge transfer in superlattices consisting of SrIrO3 and SrMnO3 is investigated using density functional theory. Despite the nearly identical work function and non-polar interfaces between SrIrO3 and SrMnO3, rather large charge transfer was experimentally reported at the interface between them. Here, we report a microscopic model that captures the mechanism behind this phenomenon, providing a qualitative understanding of the experimental observation. This leads to unique strain dependence of such charge transfer in iridate-manganite superlattices. The predicted behavior is consistently verified by experiment with soft x-ray and optical spectroscopy. Our work thus demonstrates a new route to control electronic states in non-polar oxide heterostructures.Electron density is one of the most important parameters controlling electronic phases in strongly correlated electron systems. As a milestone in condensed matter physics, high critical temperature superconductivity was discovered in Cu-based oxides by doping carriers into Mott insulating states [1]. This triggered an improvement in crystal synthesis techniques, leading to the discovery of a number of novel spin, charge and orbital states in complex oxide materials [2]. Thin film growth techniques have also improved dramatically [3,4]. In Ref.[4], Ohtomo et al. demonstrated atomically sharp interfaces between two insulating titanates with a metallic behavior. Such metallic interfaces led to the concept of electronic reconstruction originally proposed for K-doped C 60 systems [5,6]. One of the important aspects of the electronic reconstruction is that the valence state of constituent ions in such heterostructures can significantly differ from the corresponding valence state in bulk systems as a result of the electron transfer within the heterostructures. Such electron transfer can be manipulated by the polar discontinuity [7] or by the difference in the work functions [8]. The polar discontinuity was previously discussed in the context of III-V semiconductor heterostructures [9]. In this case, the discontinuity often leads to the atomic reconstruction because it is significantly more challenging to change the valence state than for transition-metal elements.Thus, hetero-structuring is expected to become a fascinating route to explore novel electronic states in complex * Copyright notice: This manuscript has been authored by UTBattelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan) † okapon@ornl.gov systems ...

Novel spin-orbit coupling driven emergent states in iridate-based heterostructures

“…A major target of such work is the realization of an appreciably sized magnetic skyrmion. The wide variety of opportunities offered by interfacial charge transfer to modulate the electron-filling and obtain a desired quantum state without explicit dopants are only just being explored [61,132]. Developments in theoretical calculations are also likely to play a key role in targeting the ideal heterostructures for the experimental realization of functional spin-orbit coupled interfaces.…”

Topological Hall effect and emergent skyrmion crystal at manganite-iridate oxide interfaces

“…The DM interaction, in bilayers of SIO and SrRuO 3 , also has been found to appear primarily near the interface [9]. The presence of an interface DM interaction is supported by the small lattice mismatch at the interface (lattice constants of SIO and LSMO are 0.394 nm [27] and 0.388 nm [28], respectively) and a strain-dependent charge transfer [29]. Because of two approximate in-plane mirror symmetries, one mirror plane involves two Mn sites and another reflects two Mn sites, it is reasonable to expect that this DM vector lies in the plane of the interface [30,31].…”

Tailoring magnetic order via atomically stacking 3d/5d electrons to achieve high-performance spintronic devices

“…The heterostructure of Mn (3d)/Ir (5d) oxides is particularly attractive because the entanglement of 3d and 5d electrons exhibit rich magnetic behaviors [4][5][6] and strong SOC [7][8][9] . For instance, emergent ferromagnetism and topological Hall effect have been reported in the SrMn 4+ O3/SrIr 4+ O3 [10][11][12] (SMO/SIO) and La0.7Sr0.3MnO3 (LSMO)/SIO 13,14 heterostructure, respectively. Moreover, through atomically control of the coupling between the iridate and manganite, a tunable in-plane ferromagnetic anisotropy characterized by both magnetization and anisotropic magnetoresistance (AMR) was reported at the La1-xSrxMnO3/SIO 15,16 heterostructures.…”