磁性绝缘体/石墨烯异质结构的输运性质研究

Graphene, a natural two-dimensional material with single atomic layer of carbon atoms, is a very promising material for the spintronics applications owing to the excellent physical, chemical and mechanical properties, especially room-temperature spin transport with long spin-diffusion lengths of several micrometres. Magnetization graphene is essential for the applications of graphene in spintronics, and also a research hotspot in graphene spintronics. Previous researches have predicted that spin-polarized electron transport and quantum anomalous hall effect could appear in graphene, through introducing the proximity effect by magnetic insulator. This project aims at the preparation of magnetic insulator/graphene functional devices by micro-nanomachining technology, to study the interfacial effect of magnetic insulator/graphene heterostructure and the modulated physical properties of graphene, especially its quantum transport properties; Through modifying nano-materials and regulating their morphology and structure, adjusting the preparation technology, to explore the influence of these parameters on the interfacial effect and physical properties of graphene, in order to make clear the relationship between structure and physical property; To explore the adjustment method of the magnetism and the quantum transport properties of graphene by external electric field, in order to observe novel quantum transport phenomena of graphene, such as quantum anomalous hall effect. These studies will contribute to further understanding spin correlation transport properties of graphene, discovering new physical effect, and providing the reference for the application of graphene in low-dissipation spintronic devices.

石墨烯是天然的单原子层结构的二维材料，具有优异的物理、化学和机械性能，其室温自旋输运相干扩散长度长达数微米，是自旋电子学应用的理想材料。磁化石墨烯对于石墨烯在自旋电子学领域的应用至关重要，也是石墨烯自旋电子学研究的一个热点。研究预测，通过磁性绝缘体材料引入邻近作用，可以使石墨烯产生自旋极化的电子输运和量子反常霍尔效应。本项目拟通过微纳加工技术制备磁性绝缘体/石墨烯功能器件，研究其异质结构的界面效应及调制后石墨烯的物理性质，特别是量子输运特性；通过改性纳米材料和调控形貌结构，调整制备工艺，探讨各参数对界面效应及石墨烯物理性质的影响，明确结构和物性的关系；探索通过外电压调节石墨烯磁性及量子输运性质的方法，以期能观测到石墨烯上新奇的量子输运现象，如量子反常霍尔效应。本项目的研究有助于进一步认识石墨烯的自旋相关输运性质，发现新的物理效应，并为石墨烯在低耗散的自旋电子器件上的应用研究提供参考。

磁化石墨烯对于石墨烯在自旋电子学领域的应用至关重要，也是石墨烯自旋电子学研究的一个热点。理论预期，引入磁性绝缘体的邻近作用可以磁化石墨烯。如果同时还引入强自旋-轨道耦合（SOC），可以打开一个拓扑非平庸的体能隙，有望实现量子反常霍尔效应。本项目采用磁性绝缘体铁酸铋(BiFeO3，简称BFO)纳米片、微机械剥离法制备的单层石墨烯，通过微纳加工技术成功制备了BFO/石墨烯的异质结构器件。通过输运测量，系统研究了在磁性绝缘体作用下石墨烯的输运性质。研究结果显示，通过磁性绝缘体BFO的磁邻近作用，成功在石墨烯上引入强交换场，实现石墨烯的自旋极化，在实验上探测到显著的自旋极化输运；通过外加垂直磁场，在此异质结构中石墨烯基态（N=0 LL）能出现量子霍尔铁磁态，在实验上观测到低耗散的螺旋型边缘态的输运。这种低耗散的边缘态输运可应用于高效的自旋电子器件。本项目的研究实现了异质界面耦合调控石墨烯的物理特性，也为实现石墨烯的量子反常霍尔效应做出一些探索工作。