Photon-assisted quantum coherent phenomena in graphene n-p and n-p-n junctions. Quantum transport in graphene based arrays of nanocrystals

本项目旨在对基于石墨烯的不同纳米结构的电荷输运中的量子力学效应进行详细的理论研究。我们的提议的一个关键点是探索在暴露于外部外加电磁场（EF）的单层和双层石墨烯中形成的横向纳米结构中相干光子辅助量子干涉效应的可能性。这些量子干涉效应是由两种石墨烯性质的结合产生的：石墨烯中准粒子的两波段无间隙光谱和准粒子与EF的局部共振相互作用，允许粒子在波段之间重新分布。量子干涉效应表现为，例如，光电流在栅极电压上的大振荡。这些振荡呈现了原子物理学中众所周知的拉姆齐量子跳动（“拉姆齐条纹”）的一种特殊实现。我们还将关注基于石墨烯的纳米晶体阵列传输中的量子现象，即集成在石墨烯纳米带中的量子点阵列，嵌入在绝缘体矩阵中的石墨烯纳米片。这种系统中的量子效应是由于石墨烯的特定电子谱、纳米晶体之间的量子力学隧道、量子涨落、库仑相互作用和无序的相互作用。这种系统中的电子输运可以从绝缘体行为变化到良好的金属行为。我们将从理论上研究接近金属-绝缘体跃迁的电导率的温度依赖性，线性和非线性电子输运的共隧道机制，栅极电压和磁场对输运的影响。所得结果对于石墨烯基纳米结构的量子电子学和量子信息处理领域具有重要意义。

This project is aimed on a detailed theoretical study of quantum-mechanical effects in the charge transport of graphene based diverse nanostructures. A key point of our proposal is to explore a possibility of coherent photon-assisted quantum interference effects in lateral nanostructures formed in monolayer and bilayer graphene, exposed to an externally applied electromagnetic field (EF). These quantum interference effects result from the combination of two graphene properties: a gapless two bands spectrum of quasiparticles in the graphene and a local resonant interaction of quasiparticles with EF allowing to re-distribute particles between bands. The quantum interference effects manifest themselves, e.g., by large oscillations of photocurrent on the gate voltage. These oscillations present a particular realization of the Ramsey quantum beating ("Ramsey fringes") well known in atomic physics. We will focus also on the quantum phenomena in the transport of graphene based arrays of nanocrystals, i.e. the arrays of quantum dots incorporated in graphene nanoribbons, graphene nanoflakes embedded into an insulator matrix. The quantum effects in such systems are due to interplay of the specific electron spectrum of graphene, quantum-mechanical tunneling between nanocrystals, quantum fluctuations, Coulomb interactions, and disorder. The electronic transport in such systems can vary from the insulator behaviour to a good metal one. We will theoretically study the temperature dependence of the conductivity close to the metal-insulator transition and the co-tunneling regime of linear and nonlinear electronic transport, the gate voltage and magnetic field influence on the transport. The obtained results are important for the fields of Quantum electronics and Quantum information processing in graphene based nanostructures.