石墨烯/LaAlO3/SrTiO3复合结构量子输运特性及库仑拖曳效应研究

Graphene and LaAlO3/SrTiO3 heterointerface are two representative two-dimensional electron gas (2DEG) systems emerging in the area of condensed matter physics and material science in recent years. Both of them possess abundant electric-field-tunable physical properties, and are highly sensitive to surface perturbations, making the study on their hybrid structure quite attractive. In this project, we will fabricate graphene/LaAlO3/SrTiO3 hybrid structure after preparing high-quality graphene and LaAlO3/SrTiO3 heterostructure separately. The effects of surface environment, proximity, and interlayer correlation on the physical properties of both graphene and LaAlO3/SrTiO3 interface will be studied, especially the modulation effects on the quantum transport properties via utilizing the abundant tunable physical properties of both layers. Besides, we will also characterize the Coulomb drag effect in this special double-layer structure, and explore the novel interlayer coupling effect between these two distinct 2DEG systems comprising of p electrons and d electrons, respectively. The fulfillment of this project will be helpful to understand the unique properties of these two representative 2DEG systems, and to discover novel quantum effects that cannot be obtained in individual system, which will shed light on the development of novel electronic devices.

石墨烯与LaAlO3/SrTiO3异质界面是近年来凝聚态物理及材料科学领域涌现出的两类代表性的二维电子气体系。二者共同具有电场可控的丰富物性，以及对表面环境较强的敏感性，使得基于二者复合结构的研究显得十分吸引人。本项目拟在分别制备高质量石墨烯以及LaAlO3/SrTiO3异质结的基础上，构筑石墨烯/LaAlO3/SrTiO3复合结构。表征这一独特体系中，表面环境、近邻效应以及层间关联作用对二者物性的影响，重点关注石墨烯与LaAlO3/SrTiO3界面可控的丰富物性对于彼此量子输运特性的调控作用。除此之外，探测这一特殊双层结构的库伦拖曳效应，理解这两类分别由p电子和d电子组成的截然不同的二维电子气体系之间新颖的层间耦合作用。我们希望通过本项目的开展，进一步加深对于这两类代表性的二维电子气体系独特物性的认识，获得在单一体系中无法实现的新颖量子效应，为新型电子学器件的发展提供有用参考。

在本项目的支持下，我们围绕二维电子体系层间相互作用，以及新型量子材料磁电特性这两个重要研究方向开展了系统的研究。取得的主要创新成果包括：1）成功构筑石墨烯与LaAlO3/SrTiO3异质界面的复合结构，实现石墨烯量子霍尔效应鲁棒性的显著提升；在LaAlO3/SrTiO3界面的超导转变附近获得了巨大的层间超流拖曳效应；2）利用石墨烯电双层结构揭示了无质量费米子和有质量费米子之间长程耦合的指纹特性；3）通过界面应力工程，在低维关联氧化物中实现电子相的摩尔调控；4）实验发现包括外尔半导体在内的若干新型拓扑材料。在该项目执行期间，共发表SCI论文9篇，包括1篇Nat. Phys.，1篇PNAS，2篇Nano Lett.和2篇Chin. Phys. Lett.。