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Coherent phonons in carbon nanotubes and graphene
Kim, J.H.,Nugraha, A.R.T.,Booshehri, L.G.,Haroz, E.H.,Sato, K.,Sanders, G.D.,Yee, K.J.,Lim, Y.S.,Stanton, C.J.,Saito, R.,Kono, J. Elsevier Science Publishers [etc.] 2013 Chemical physics Vol.413 No.-
We review recent studies of coherent phonons (CPs) corresponding to the radial breathing mode (RBM) and G-mode in single-wall carbon nanotubes (SWCNTs) and graphene. Because of the bandgap-diameter relationship, RBM-CPs cause bandgap oscillations in SWCNTs, modulating interband transitions at terahertz frequencies. Interband resonances enhance CP signals, allowing for chirality determination. Using pulse shaping, one can selectively excite specific-chirality SWCNTs within an ensemble. G-mode CPs exhibit temperature-dependent dephasing via interaction with RBM phonons. Our microscopic theory derives a driven oscillator equation with a density-dependent driving term, which correctly predicts CP trends within and between (2n+m) families. We also find that the diameter can initially increase or decrease. Finally, we theoretically study the radial breathing like mode in graphene nanoribbons. For excitation near the absorption edge, the driving term is much larger for zigzag nanoribbons. We also explain how the armchair nanoribbon width changes in response to laser excitation.
Polarization anisotropy of transient carrier and phonon dynamics in carbon nanotubes
Kim, Ji-Hee,Park, Jaegyu,Lee, Bong Yeon,Lee, Donghan,Yee, Ki-Ju,Lim, Yong-Sik,Booshehri, Layla G.,Há,roz, Erik H.,Kono, Junichiro,Baik, Sung-Hoon American Institute of Physics 2009 JOURNAL OF APPLIED PHYSICS - Vol.105 No.10
Lim, Yong-Sik,Ahn, Jae-Geum,Kim, Ji-Hee,Yee, Ki-Ju,Joo, Taiha,Baik, Sung-Hoon,Há,roz, Erik H.,Booshehri, Layla G.,Kono, Junichiro American Chemical Society 2010 ACS NANO Vol.4 No.6
<P>We have observed large-amplitude coherent phonon oscillations of radial breathing modes (RBMs) in single-walled carbon nanotubes excited through the lowest-energy (<I>E</I><SUB>11</SUB>) interband transitions. In contrast to the previously studied coherent phonons excited through higher-energy (<I>E</I><SUB>22</SUB>) transitions, these RBMs show comparable intensities between (<I>n</I>−<I>m</I>) mod 3 = +1 and −1 nanotubes. We also find the novel observation of RBMs excited over an excitation range of ∼300 meV above the <I>E</I><SUB>11</SUB> transition, which we attribute to possible resonance with phonon sidebands of the lowest optical transition, arising from strong exciton−phonon coupling.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-6/nn100055e/production/images/medium/nn-2010-00055e_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn100055e'>ACS Electronic Supporting Info</A></P>