4d过渡金属Rh氧化物薄膜的物性研究

The competition and coupling of multiple freedoms (i.e., spin, orbit, charge, and lattice) in correlated electron materials is one of the hot topics in condensed matter physics. The 4d transition metal oxides (TMO), such as ARhO3, which are close to the Mott-Hubbard Limitation, are important objects in this field. In general, 4d Rhodium oxides have relative larger orbital radius, larger electron band width, weaker on-site coulomb interaction, weaker Hund’s coupling energy, and larger spin-orbit coupling. Rhodium oxides have special transport and magnetization properties. However, the correlated mechanism in such system is not clear up to now. Moreover, some of them are difficult for the fabrication which prevents the systematic exploring in this system. In this proposal, we plan to do research on the 4d Rhodium oxide films from the viewpoint of strain effect systematically. The main topic of this research will be focus on the tuning of lattice by strain in the films. In detail, the Rh-based TMO films with perovskite structure will be fabricated by pulsed laser ablation technique, the high magnetic field will be used to extend our measurement range, and the strain effect will be studied carefully to explore the role of lattice in the competition and coupling of multiple freedoms. We expect to obtain much knowledge about the importance of lattice and the mechanism of multiple freedom competition and coupling in the 4d TMO system through this study. We hope our research can provide useful information for the understanding of correlated electron materials.

关联电子体系中多自由度（自旋、轨道、电荷及晶格）竞争与合作的关系一直是凝聚态物理学的研究焦点之一。其中，本征能量接近Mott-Hubbard极限的4d过渡金属Rh氧化物具有拓展的轨道半径与电子带宽，其晶场劈裂能、轨道杂化强度、电荷转移能和在位库伦相互作用能量接近，是这一研究领域不可或缺的研究对象。Rh氧化物具有独特的电磁特性，其外场调控行为及其机理尚不清晰；而且体系中很多材料的制备条件苛刻、开展系统研究具有一定难度。本项目建议以晶体场能调控为窗口，以Rh氧化物外延薄膜为对象，开展4d过渡金属氧化物的物性研究。项目通过薄膜生长方式解决材料制备中的困难，通过应力调控方式重点研究晶体场能对关联物性的影响，在研究关联物性随应力作用演变规律的基础上，阐明晶格自由度在Rh氧化物多自由度竞争中的作用，为深入理解关联电子材料的物理内涵提供实验基础。

本项目以具有钙钛矿结构的p型氧化物半导体LaRhO3薄膜与异质结为主要研究对象，采用磁场下的电、磁、光敏等特色技术手段，系统研究过渡金属复杂氧化物的关联电子物性，获得其随外场变化的规律，探索其功能应用。.项目团队不仅通过脉冲激光沉积系统，生长了系列3d、4d 过渡金属氧化物薄膜与异质界面，而且在其中：1）国际上首次发现了3d过渡金属氧化物中高温多重电子序的晶体学行为，并用20T级的强磁场下MFM观察到了电子晶体的实空间图像与其动力学行为；2）发现了新型p型氧化物半导体LaRhO3的光电导性能被异轨道界面状态有效调控效应；3）发现了钙钛矿结构的三元氧化物LaRhO3薄膜中优异的气敏性质；4）获得了金属-3d金属氧化物异质结的电疲劳特性，在疲劳的异质结中采用SHG 技术发现了疲劳导致的预铁电态，以及极化整流效应；5）采用磁场下超快泵浦-探测技术探索了3d/4d 异轨道界面的超快动力学行为等等。.本项目支持的工作共计发表SCI论文13篇，其中ACS Appl. Mater. Interfaces一篇、Adv. Optical Mater.一篇，Appl. Phys. Lett. 两篇。另外，还有准备和在投的4篇，预计2020发表。