Browsing by Author "Haroz, E.H."

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    Circular polarization dependent cyclotron resonance in large-area graphene in ultrahigh magnetic fields
    (American Physical Society, 2012) Booshehri, L.G.; Mielke, C.H.; Rickel, D.G.; Crooker, S.A.; Zhang, Q.; Ren, L.; Haroz, E.H.; Rustagi, A.; Stanton, C.J.; Jin, Z.; Sun, Z.; Yan, Z.; Tour, J.M.; Kono, J.
    Using ultrahigh magnetic fields up to 170 T and polarized midinfrared radiation with tunable wavelengths from 9.22 to 10.67 μm, we studied cyclotron resonance in large-area graphene grown by chemical vapor deposition. Circular polarization dependent studies reveal strong p-type doping for as-grown graphene, and the dependence of the cyclotron resonance on radiation wavelength allows for a determination of the Fermi energy. Thermal annealing shifts the Fermi energy to near the Dirac point, resulting in the simultaneous appearance of hole and electron cyclotron resonance in the magnetic quantum limit, even though the sample is still p-type, due to graphene's linear dispersion and unique Landau level structure. These high-field studies therefore allow for a clear identification of cyclotron resonance features in large-area, low-mobility graphene samples.
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    Dephasing of G-band phonons in single-wall carbon nanotubes probed via impulsive stimulated Raman scattering
    (American Physical Society, 2012) Kim, J.-H.; Yee, K.-J.; Lim, Y.-S.; Booshehri, L.G.; Haroz, E.H.; Kono, J.
    We study the coherent dynamics of G-band phonons in single-wall carbon nanotubes through impulsive stimulated Stokes and anti-Stokes Raman scattering. The probe energy dependence of the phonon amplitude as well as the preferential occurrence between Stokes and anti-Stokes components in response to chirpedpulse excitation are well explained within our model. The temperature dependence of the observed dephasing rate clearly exhibits a thermally activated component, with an activation energy that coincides with the frequency of the radial breathing mode (RBM). This fact provides a clear picture for the dephasing of G-band phonons by random frequency modulation via interaction with the RBM through anharmonicity.