微波场作用下石墨烯二维电子气的量子输运研究

The quantum transport properties of the two-dimension electron gas in graphene are very important for the design of new quantum devices based on graphene. In this project, we will prepare high mobility graphene monolayers by micromechanical cleavage of graphite and transferring graphene to boron nitride substrates. The samples will be processed into the standard Hall bar structure using electron beam lithography and the gate electrode will also be fabricated. By means of magnetotransport measurements at low temperature under microwave illumination, we will investigate the microwave influence on the quantum transport behavior of graphene, for example, quantum Hall effect, Shubnikov-de Haas oscillations, weak localization and weak antilocalization effect. We will devote ourselves to explore new phenomena induced by microwave fields in graphene systems, for example, microwave-induced resistance oscillations (MIRO) and zero-resistance states (ZRS), magnetoplasmon resonance (MPR), electron spin resonance (ESR), microwave-induced dephasing and so on. We will not only extract some important physical parameters such as effective mass, g-factor, transport/quantum mobility, spin relaxation time, dephasing time and intra-/inter-valley scattering time, but also investigate the modulation of these parameters by microwave fields and gate voltage. Our project will probably discover new microwave-induced physical effect and modulation in graphene, and provide useful references for the development of new materials and spintronics.

研究石墨烯二维电子气的量子输运性质对设计基于石墨烯的新型量子器件具有重要意义。本项目将使用微机械剥离法从石墨上剥离石墨烯，并将其转移到硼氮衬底上，制备高迁移率单层石墨烯。通过电子束光刻制备Hall bar结构并加工栅极。通过微波辐照下的低温磁输运测试，研究微波对石墨烯量子输运行为（量子霍尔效应、Shubnikov-de Haas振荡、弱局域和反弱局域效应等）的影响。致力于在石墨烯体系中观察到微波场引起的新颖效应（微波诱发磁阻振荡（MIRO）和零电阻态（ZRS）、磁致等离激元共振（MPR）、电子自旋共振（ESR）、微波引起电子退相等）。由此获得载流子有效质量、g因子、输运迁移率和量子迁移率、自旋弛豫时间、退相干时间、谷内和谷间散射时间等重要物理量，并研究微波场和栅压对这些物理量的调控作用。本项目有希望发现石墨烯在微波场作用下的新奇物理效应和调控规律，为新型材料和自旋电子学的发展提供有用参考。

研究石墨烯二维电子气的量子输运性质对设计基于石墨烯的新型量子器件具有重要意义。在本项目资助下，我们制备了石墨烯与过渡金属氧化物异质结LaAlO3/SrTiO3、石墨烯与超导体NbSe2、石墨烯与磁性绝缘体LaMnO3及EuS、石墨烯与金纳米颗粒阵列、石墨烯与有机分子周期条带、以及石墨烯与氮化硼等功能材料的近邻复合结构器件。对这些器件进行了常规和电磁波辐照下的低温磁输运测试。观察到石墨烯光电导响应的增强，实现了石墨烯弱局域量子干涉效应的电磁波调控，观察到微波场引起石墨烯载流子的退相，实现了石墨烯周期势阱光吸收谱的调控，实现了氧化物界面自旋轨道耦合的栅压非单调调控和电磁波非易失可擦除调控，观察到石墨烯在第二类超导体近邻下的磁阻平台，观察到石墨烯在磁性绝缘体近邻下的非对称磁阻和非线性霍尔效应。实现了电磁波场和栅压对载流子浓度和迁移率、相位相干长度、谷内和谷间散射长度、自旋轨道耦合强度等重要物理量的调控。研究结果在石墨烯的光电探测领域具有应用前景，为探索石墨烯的非平凡量子态以及光控量子器件提供了线索。已发表标注资助的SCI论文5篇，其中通讯作者论文4篇；共培养3名博士研究生毕业，1名博士后出站。