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Electron-phonon interaction in uniaxial strained graphene : Fingerprints of the electronic dispersion in Raman and magneto-Raman spectra

Vendredi 13 novembre 2015 09:30 - Duree : 1 heure
Lieu : LNCMI, salle de conférences "René Pauthenet" (bâtiment J, 2ème étage) - 25 rue des martyrs - 38000 Grenoble

Orateur : Sonia HADDAD (Laboratoire de Physique de la Matière Condensée, Département de Physique, Faculté des Sciences de Tunis, Université Tunis El Manar, Campus Universitaire 1060 Tunis, Tunisia)

In this talk, I discuss the effect of the characteristics of the electronic band structure of the uniaxial strained graphene on the electron phonon interaction and how to bring out this effect in Raman spectra. I focus on the Raman G band corresponding to the center zone optical phonons.

I will present the model we proposed to derive the frequency shifts and the broadening of the longitudinal optical (LO) and the transverse optical (TO) phonon modes, due to electronphonon interaction. I will show that, in the absence of a shear strain component, such interaction gives rise to a lifting of the degeneracy of the LO and the TO modes which contributes to the splitting of the G Raman band. Moreover, the anisotropy of the electronic spectrum induced by the strain, is found to result in a polarization dependence of the LO and TO modes. This dependence is in agreement with the experimental results showing a periodic modulation of the Raman intensity of the split G peak.

I will then discuss the possibility to induce a double-peak structure in the magneto-phonon resonance (MPR) spectrum of uniaxial strained graphene, under crossed electric and magnetic fields. We focus on the Γ point optical phonon modes coupled to the inter-Landau level transitions 0 ±1 where MPR is expected to be more pronounced at high magnetic field. We show that the MPR lines acquire a double resonance structure originating from the two-fold valley degeneracy lifting. The latter is due to the different Landau level spacings in the two Dirac valleys resulting from the simultaneous action of the inplane electric field and the strain induced Dirac cone tilt. I will discuss the role of some key parameters such as disorder, strain, doping and electric field amplitude on the emergence of the double resonance structure.

Contact : Marek.Potemski@lncmi.cnrs.fr

Discipline évènement : (Physique)
Entité organisatrice : (LNCMI)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire LNCMI)
Site de l'évènement : Polygone scientifique

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