Browsing by Author "Kim, Y."

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    Effects of electron-electron interactions on the electronic Raman scattering of graphite in high magnetic fields
    (American Physical Society, 2014) Ma, Y.; Kim, Y.; Kalugin, N.G.; Lombardo, A.; Ferrari, A.C.; Kono, J.; Imambekov, A.; Smirnov, D.
    We report the observation of strongly temperature (T)-dependent spectral lines in electronic Raman-scattering spectra of graphite in a high magnetic field up to 45 T applied along the c axis. The magnetic field quantizes the in-plane motion, while the out-of-plane motion remains free, effectively reducing the system dimension from 3 to 1. Optically created electron-hole pairs interact with, or shake up, the one-dimensional Fermi sea in the lowest Landau subbands. Based on the Tomonaga-Luttinger liquid theory, we show that interaction effects modify the spectral line shape from (ω−Δ)−1/2 to (ω−Δ)2α−1/2 at T = 0. At finite T, we predict a thermal broadening factor that increases linearly with T. Our model reproduces the observed T-dependent line shape, determining the electron-electron interaction parameter α to be ∼0.05 at 40 T.
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    Measurement of Filling-Factor-Dependent Magnetophonon Resonances in Graphene Using Raman Spectroscopy
    (American Physical Society, 2013-05-29) Kim, Y.; Poumirol, J.M.; Lombardo, A.; Kalugin, N.G.; Georgiou, T.; Kim, Y.J.; Novoselov, K.S.; Ferrari, A.C.; Kono, J.; Kashuba, O.; Fal’ko, V.I.; Smirnov, D.
    We perform polarization-resolved Raman spectroscopy on graphene in magnetic fields up to 45 T. This reveals a filling-factor-dependent, multicomponent anticrossing structure of the Raman G peak, resulting from magnetophonon resonances between magnetoexcitons and E2g phonons. This is explained with a model of Raman scattering taking into account the effects of spatially inhomogeneous carrier densities and strain. Random fluctuations of strain-induced pseudomagnetic fields lead to increased scattering intensity inside the anticrossing gap, consistent with the experiments.