Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS


MOMB Streszczenie raportu

Project ID: 320590
Źródło dofinansowania: FP7-IDEAS-ERC
Kraj: France

Mid-Term Report Summary - MOMB (Magneto-optics of layered materials: exploring many-body physics in electronic systems with unconventional bands)

The ERC MOMB project is devoted to the study of electronic properties of graphene-based, topological insulator, and transition metal dichalcogenides materials. Its ultimate focus is the investigation of the effects of interactions: electron-electron and electron-phonon. The leading experimental technique used for the studies is optical magneto-spectroscopy, in the spectral range from microwaves, via far-infrared to visible optics, supported when necessary by magneto-transport methods. On the technical side, the project consists of the development of a new experimental set-up (micro-magneto-Raman scattering facility) and the in-house competence to fabricate, by mechanical exfoliation, the structures of thin films extracted from layered materials (graphite and bulk crystals of transition metal dichalcogenides).

The main technical goals of the project have been completed. The micro-magneto-Raman scattering facility is well operational, including the experimentations at high magnetic fields (30 T) and low helium-bath temperatures. The developed free-beam probe in conjunction with the triple Raman spectrometer (funded by this grant) permits the high resolution magneto-optical experiments and/or probing the Raman scattering signal as close as 20cm-1 from the laser line. With the developed in-house methods of sample fabrications (exfoliation and transfer techniques under ambient conditions) we are now able to fabricate the high quality structures made of various materials (graphite, hexagonal boron nitride and semiconducting transition metal dichalcogenides) and master the deterministic transfer techniques.

The results of the research activity which wholly or partially resulted from the project include:
-demonstration of the magneto-phonon resonance in CVD-grown graphene and switching on and off this resonance by the electric field;
-identification of electronic excitations in the magneto-Raman scattering response of single-, bi-, tri-, tetra- and penta-layers of suspended graphene structures and exploration of these results to tackle the characteristic band structure of each Bernal stacked multilayer graphene;
-studies of electronic excitations in graphene on graphite, which uncover an entirely new class of magneto-phonon resonances which were possible to be visualized in this graphene system of the unprecedented electronic quality;
-identification of the many-body corrections to inter Landau level excitations in graphene with different dielectric environments;
-demonstration of the surprisingly strong efficiency of the Auger recombination processes between Landau levels of graphene;
- discovery of the fractal pattern (Hofstadter butterfly) of Landau levels in graphene specially oriented on hBN (lateral periodic modulation caused by the induced moiré pattern) and uncovering the effects of electron-electron interactions (quantum Hall ferromagnetism) characteristic of Landau levels of the main and replicate Dirac cones in quantized graphene;
-uncovering the many-body opening of the energy gap (insulating phase) in tetra-layer, and likely in all even but not odd N-layers of Bernal stacked graphene;
-demonstration of symmetry breaking effects in epitaxial graphene at very high magnetic fields;
-demonstration of the shape of electronic bands in the form of three-dimensional Dirac cones in zero-gapped, zinc-blende HgCdTe crystals;
-magneto-transport, NMR and magneto-optical studies of bulk Bi2Se3, and simplified modeling of the band structure of Bi2Se3 by a cartoon image of the particle-antiparticle Dirac spectrum of massive fermions in the nonrelativistic limit;
- characterization of the optical properties (Raman scattering and optical-reflectivity) of thin layers of semiconducting transition metal dichalcogenides (MoS2, WSe2) and demonstration of single photon emitters associated to WSe2 monolayers.

The publication output, wholly or partially related to this project, during its mid-term 30-months of activity, consists of 19 scientific articles, including those in Nature (1), Nature Physics (3), Nature Nanotech.(1), Phys. Rev. Lett.(2), Nature Comm.(1) and Nano Letters(4).

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