arXiv subjects

N. G. Kalugin

Publications and source records attributed to N. G. Kalugin.

3 recordsLinked to original sources

arXiv2013

Measurement of Filling-Factor-Dependent Magnetophonon Resonances in Graphene Using Raman Spectroscopy

We perform polarization-resolved Raman spectroscopy on graphene in magnetic fields up to 45T. This reveals a filling-factor-dependent, multi-component anticrossing structure of the Raman G peak, resulting from magnetophonon resonances between magnetoexcitons and E$_{2g}$ 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 pseudo-magnetic fields lead to increased scattering intensity inside the anti-crossing gap, consistent with the experiment.

cond-mat.mes-hall↗

arXiv2013

Effects of Electron-Electron Interactions on Electronic Raman Scattering of Graphite in High Magnetic Fields

We report the observation of strongly temperature-dependent, asymmetric 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 three to one. 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 van Hove singularity to the form $(ω-Δ)^{2α-1/2}$ at zero temperature. At finite temperature, we predict a thermal broadening factor that increases linearly with the temperature. Our model reproduces the observed temperature-dependent line-shape, determining $α$ to be $\sim$0.05 at 40 T.

cond-mat.mes-hall↗

arXiv2012

Magnetophonon resonance in graphite: High-field Raman measurements and electron-phonon coupling contributions

We perform Raman scattering experiments on natural graphite in magnetic fields up to 45 T, observing a series of peaks due to interband electronic excitations over a much broader magnetic field range than previously reported. We also explore electron-phonon coupling in graphite via magnetophonon resonances. The Raman G peak shifts and splits as a function of magnetic field, due to the magnetically tuned coupling of the E2g optical phonons with the K- and H-point inter-Landau-level excitations. The analysis of the observed anticrossing behavior allows us to determine the electron-phonon coupling for both K- and H-point carriers. In the highest field range (>35 T) the G peak narrows due to suppression of electron-phonon interaction.

cond-mat.mes-hall↗