基于超晶格能隙的门电压定义的石墨烯量子点接触

项目名称： 基于超晶格能隙的门电压定义的石墨烯量子点接触

项目编号： No.11504385

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 数理科学和化学

项目作者： 韩拯

作者单位： 中国科学院金属研究所

项目金额： 24万元

中文摘要： 在二维电子气中，门电压是常用的定义纳米结构的手段。然而，对于单层石墨烯而言，由于不存在能隙，门电压并不能将所覆盖样品区域调制成绝缘态，从而无法实现门电压定义的约束结构。在宏观体系中引入带隙的方法通常可以是霍尔效应下朗道能隙。近年来发展起来的石墨烯－氮化硼超晶格被报道在零场下将在石墨烯狄拉克点附近引入带隙，低温下呈绝缘态。这个特殊效应给我们提供了用此设计门电压来定义新型纳米结构的可能性。例如，在石墨烯－氮化硼异质结中引入两组电门，一组保持门电压覆盖的样品区域保持在狄拉克点附近的绝缘态，另一组用来调控其它区域的载流子浓度，从而达到调制量子点接触的电子输运的目的。零场下量子化的电导台阶是我们实验上将要寻找的特征信号。我们还将研究在较高磁场下体系进入量子霍尔态之后，边缘态在量子点接触附近的散射和耦合机制。此外，门电压定义的量子点接触还可以拓展至一维势阱等纳米结构，并用于MoS2等其它二维材料。

中文关键词： 低维纳米结构；石墨烯－氮化硼异质结；超晶格

英文摘要： In conventional 2D electron gases (2DEG), gate-confinement is one of the most common ways to realize various nano-structures. However, due to the lack of a band-gap, monolayer graphene can not be gate-defined into an insulating state, thus is not able to be gate-defined into quantum confinement. The ways to induce a gap in such a system include quantum Hall cyclotron gap. The recently emerging graphene-bonron nitride super lattice causes the so-called Hofstadter butterfly energy spectrum, which basically induces a gap at the charge neutrality point at zero magnetic field. This remarkable effect provides us an unique opportunity to engineer nanosturctures by a electrical gate, since maintaining at Dirac point is now equal to maintaining a insulating state, thus allows one to have any nanostructure as the case for GaAs 2DEG. Based on this motivation, we here propose a research project of fabricating new type of quantum point contact (QPC) which utilizes the gap formed in the well-known BN-graphene super-lattice. The super-lattice gap based QPC will be formed with two sets of gates, one control the insulating area near the Dirac peak, the other tuning the conduction channel. Quantized conductivity is expected at zero magnetic field. We will also study the electron trasnport at high enough magnetic field where the the quantum Hall edge states interact at the crossing point of QPC confinement defined by the top gtae. Systems such as MoS2 and other nano-structures are possible using our technique.

英文关键词： low dimensional nanostricture;graphene/BN heterostructure;super-lattice