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

• Applicant: Professor Dr. Konstantin Efetov (†)
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 173138112

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.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1459: Graphen