QUANTUMPHANOGRAPHENE · Quantum Interference and electro-PHonon ANOmalies in graphenes
FP7 — People (Marie Curie Actions)
- Duration
- 2011-02-15 → 2013-02-14
- EU contribution
- €205,678
- Participants
- 1
- Scheme
- MC-IEF
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Results in brief
Quantum Interference and electro-PHonon ANOmalies in graphenes
Graphenic systems represent nowadays one of the most important research topics in physics, because of their potential applications in new designed electronic devices. Fundamental in this regards is the study of their electronic an transport properties. On the other hand, such properties are themselves determined at a large extend by the strength and nature of the electron-lattice interaction and by the lattice dynamics. Understanding and controlling this issue is thus of highest importance. The project has addressed an important argument in this field concerning the identification of the microscopic mechanisms controlling the infrared activity of the optical phonons in these materials and their interaction with the electronic excitations. The objectives of this work have been twofold: on one hand to proof at a quantitative level how the analysis of the spectral properties of the optical phonon can represent a powerful tool to characterize the multilayer graphene materials, for instance the number of layers, the stacking order, the presence of a bandgap, the intrinsic doping level by the substrate and the controlled doping induced by field effects. At the same time, the analysis of the phonon anomalies reveals in a direct way the mechanisms ruling the properties of the electron-lattice interaction, giving rise to characteristic Fano asymmetry of the phonon lineshapes. The project has successfully address this investigation providing a fundamental progress in the field. Moreover, in the course of the developing of the project, the continuous progresses in the field have triggered on the stage additional topics regarding the physical properties of other two-dimensional materials, like MoS2 and other dichalcogenides, that present similar properties as graphene but with the advantage of being insulating. Due to the high-impact relevance of these new issues in the scientific field, the developing of the project has also included, with a proper timeliness, a careful investigation of the physical properties of these materials in regards to their electronic, screening, superconducting and electro-elastic properties.
Data: CORDIS, © European Union
Project objective
Graphenic systems represent nowadays one of the most important research topics, because of their potential applications in new designed electronic devices. Most promising are the bilayer and multi-layered compounds where a controlled gap can be induced by field effect. Besides their peculiar transport properties, graphenes present also interesting phonon anomalies, usually probed by means of Raman spectroscopy. The theoretical and experimental investigation of such features has been shown to provide a useful tool to determine in a non destructive way the fundamental characteristics of the samples, as the number of layers, the induced charge density and the magnitude of the gap itself. Very recently, first observations of phonon anomalies in bilayer graphenes have been reported also in the optical conductivity, where the phonon peaks were shown to have a marked asymmetric Fano-like shape, characteristic of a strong quantum interference with the particle-hole excitations. Such asymmetry, as well the intensity of the phonon peak itself, results moreover to have a strong dependence on the external gate voltage. Aim of the present project is to provide a theoretical model to explain on a microscopic ground the nature of these phonon anomalies in the optical conductivity. Within this context, the presence itself of a finite phonon intensity in homoatomic systems as graphenes is by no means trivial and it needs to be specifically addressed. Particular relevance acquires also the investigation of the origin of the Fano shape whose presence provides a direct probe of the particle-hole excitations coupled with the electron-phonon interaction. The comparison with the Raman measurements will also shed light on the different interband excitations involved in the different probes. Within this context the role of the substrate and of external gate voltages will be also included in order to provide a compelling comparison with the experimental measurements in a realistic setup.
Original text from CORDIS.
Participants
- AGENCIA ESTATAL CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS · MadridCoordinatorSpain
Links
Data: CORDIS, © European Union