关联半金属SrIrO3薄膜和超晶格的有序磁结构的产生、演化和调控

The modulation of novel quantum behaviors induced by the competition among multiple degrees of energy is the central topic of the recent national research strategy . SrIrO3 is a typical paramagnetic correlated semimetal caused by multiple degrees competition of energy, and is predicted showing novel quantum states including topological phase. This project focuses on creating magnetic order in SrIrO3 through quantum size effect and strain engineering, and reveals its creation mechanism by researching its dependence on the band structure so on the spin orbit coupling, the electron correlation and the crystal field. Concretely, the obstacles in magnetism measurement will be overcome through supperlattic construction; the effect of quantum size effect on the magnetic order would be realized by tuning the thickness of SrIrO3 layer in the superlattice (SrIrO3/SrTiO3)n and (SrIrO3/LaAlO3)n. Furtherly, the stain effect will be introduced by different interlayer (SrTiO3, LaAlO3), the thickness of the interlayer also will be tuned to research the possible exchange coupling coming from the magnetic ordering layer SrIrO3 in the superlattice. The bans structure and evolution of the multiple degrees of energy will be explored through such as the electron transport detection under varying temperature and magnetic fields, as well as the optical conduction measurement. This project will shed new light on quantum propeties origination and modulation of 5d iridates family.

多相互作用竞争及其诱导量子效应调控是我国近阶段科研规划的关键任务。SrIrO3是典型的多相互作用竞争导致顺磁关联半金属，被预期存在拓扑相等新奇物态。项目欲通过制备(SrIrO3/SrTiO3)n和(SrIrO3/LaAlO3)n超晶格引入量子限制效应和应变在SrIrO3薄膜中诱生出有序磁结构，并通过调节SrIrO3层厚度研究诱生磁结构与量子限制效应的关联，比较(SrIrO3/SrTiO3)n和(SrIrO3/LaAlO3)n超晶格的磁学性质以研究应变对诱生磁结构的调控，调节SrTiO3中间层厚度探索(SrIrO3/SrTiO3)n超晶格可能存在的SrIrO3磁性层间的耦合行为。此外，通过对不同条件下SrIrO3超晶格的电输运、磁输运、光电导等物性的研究阐明相应能带结构和各相互作用强度的演化规律, 探究它们与磁结构演化间关系。可为深入认识5d铱氧化物量子物性起源和调控奠定基础。

强旋轨耦合材料及其奇异物性已成为当前材料科学及凝聚态物理研究的前沿。SrIrO3为典型的强旋轨耦合钙钛矿5d轨道氧化物。理论预言SrIrO3为半金属，且在费米面附近具有拓扑狄拉克锥，因而对于开辟新的氧化物拓扑相材料具有重要意义， 然而当前相关实验工作尚不充分；另一方面，理论上SrIrO3的强旋轨耦合作用应能调控与其接触的磁性材料的自旋序结构，相关的实验研究正处于起步阶段。该项目细致研究了SrIrO3薄膜的电子输运特性和电子结构，观测到非线性霍尔效应，给出了SrirO3 为半金属的电输运证据。进一步探测了衬底应变限制对SrIrO3薄膜电子输运特性和电子结构的调控行为，实验结果表明SrIrO3电子结构对应变敏感，压应变可使空穴价带偏离费米面，明显抑制SrIrO3薄膜电输运中的空穴载流子贡献，为人工调控SrIrO3电/磁性能奠定了实验基础。在SrRuO3/SrIrO3 超晶格中观测到低温自旋玻璃行为和拓扑霍尔效应，表明SrIrO3层的强旋轨耦合作用通过增强了异质界面处Dzyaloshinskii-Moriya效应，使界面处SrRuO3中自旋形成了非共线有序结构，预示可能形成了特殊的Skyrmion准粒子。这一研究成果证明了SrIrO3层旋轨耦合作用可有效调控与其接触磁性材料的磁序结构和磁学特性，是引领SrIrO3/磁体异质结构这一研究方向的基础性工作。项目取得成果为本课题组及国内外相关研究小组进一步深入研究基于SrIrO3的异质体系、氧化物拓扑物态和自旋电子学奠定了实验基础，具有重要的科学意义和影响力。