Development of single Dirac-particle devices

石墨烯由单层碳原子组成，其量子点(QD)器件是人们研究的热点。在大多数以前制造这种器件的尝试中，这些结构是通过光刻从石墨烯薄片上刻蚀出来的，得到的器件由连接到引线部分的量子点和小收缩组成。因此，石墨烯量子点或纳米带器件的输运特性往往受到边缘粗糙度和无序性的影响。针对这种情况，我们提出了一种新的器件结构，在这种结构中，石墨烯纳米结构被隔离，金属接触直接沉积在其上而不受约束。我们证明了库仑封锁效应是在垂直于石墨烯薄层的均匀磁场下演化的，这表明在磁场的作用下发生了量子限制-解禁闭转变。这一演示是控制石墨烯电子学中单个狄拉克费米子的重要进展。

Graphene consists of a single layer of carbon atoms and its quantum-dot (QD) devices are of significant research interest. In most previous attempts to fabricate such devices, the structures were etched from a graphene sheet by lithography, and the resulting devices consisted of QDs and small constrictions connected to the lead parts. Therefore, transport properties of graphene QD or nanoribbon devices are often dominated by edge roughness and disorder.To address this situation, we propose a new device structure, in which graphene nanostructures are isolated and metallic contacts are directly deposited onto them without constrictions. We demonstrate that the Coulomb-blockade effect evolves under a uniform magnetic field perpendicular to the graphene sheet, which indicates the quantum confinement-deconfinement transition switched by a magnetic field. This demonstration constitutes important advances to control single Dirac fermions in graphene electronics.