Development of single Dirac-particle devices

石墨烯由单层碳原子组成，其量子点（QD）器件具有重要的研究意义。在之前制造这种器件的大多数尝试中，结构都是通过光刻技术从石墨烯片上蚀刻出来的，并且最终的器件由量子点和连接到引线部分的小约束组成。因此，石墨烯量子点或纳米带器件的输运性质通常由边缘粗糙度和无序性决定。为了解决这种情况，我们提出了一种新的器件结构，其中石墨烯纳米结构是隔离的，金属触点直接沉积在其上而不受约束。我们证明了库仑-封锁效应在垂直于石墨烯片的均匀磁场下发生，这表明了由磁场开关的量子约束-非约束跃迁。该演示是石墨烯电子中控制单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.