Magneto-Raman Scattering of Graphene on Graphite: Electronic and Phonon Excitations

Abstract

Magneto-Raman-scattering experiments from the surface of graphite reveal novel features associated to purely electronic excitations which are observed in addition to phonon-mediated resonances. Graphene-like and graphite domains are identified through experiments with ∼1 μm spatial resolution performed in magnetic fields up to 32 T. Polarization resolved measurements emphasize the characteristic selection rules for electronic transitions in graphene. Graphene on graphite displays the unexpected hybridization between optical phonon and symmetric across the Dirac point inter Landau level transitions. The results open new experimental possibilities--to use light scattering methods in studies of graphene under quantum Hall effect conditions.

Plasmonic excitations in Coulomb-coupledN-layer graphene structures

“…Particularly, electron-phonon interaction phenomena have become a subject of active study in single-layer graphene structures in zero [16][17][18][19] and finite magnetic fields [20][21][22][23] . Substantial efforts have been directed towards the investigation of the linear response of doped graphene 24 and of the charge density excitations [25][26][27][28][29] and of such complex quasiparticles as plasmarons 30,31 and plasmon-phonon complexes 32 .…”

Theory of inter-Landau-level magnetoexcitons in bilayer graphene

“…11,48 Unlike for the conventional twodimensional electron gas with a quadratic dispersion, 54 the excitations in a quantizing magnetic field do acquire an interaction shift; the magnitude of such a shift is one of our experimental predictions.…”

“…[6][7][8] The gap at the integer quantum Hall effect at filling factor ν = ρhc/eB ⊥ = ±4, ±8 has been recently measured with great accuracy, 9 and the excitations of the IQHE states in the long wavelength limit have also been observed by infrared absorption 10 and Raman spectrocopy. 11 Further broken symmetry states have been observed [12][13][14][15][16] in the central Landau band at ν = 0, ±1, ±2 and ±3, and by careful tilted-field measurements it has been shown that they arise predominantly from many-body effects, i.e., from quantum Hall ferromagnetism (QHF). 17 Quantum Hall states with broken symmetry have also been found in the n = −2 Landau level 18 , and there is also some evidence for a fractional quantum Hall plateau.…”

“…In the low magnetoexciton density limit the interaction between magnetoexcitons is neglected. The mean-field (Hartree-Fock) Hamiltonian of magnetoexcitons is well known from the literature, 37-40 and so is its adaptation to spinorial orbitals: 35,50,51 (11) where N = (n, ξ, σ), etc., and δ N N ′ = δ σσ ′ δ ξξ ′ δ nn ′ . The first term of the r.h.s.…”

“…Some of these modes couple to circularly polarized light, 41 while others may be observable in inelastic light scattering experiments. 11,[42][43][44][45][46][47][48] For monolayer graphene Yang et al 49 studied the intra-Landau level excitations of quantum Hall ferromagnetic states, and Iyengar et al, 50 Bychkov and Martinez, 51 Roldán et al, 52 and Lozovik and Sokolik 53 discussed the inter-Landau level excitations in detail both for the IQHE and QHF states. In particular, the linear dispersion of electrons and holes in graphene makes Kohn's theorem 54 inapplicable.…”