Real carbon nanotubes12/26/2023 ![]() ![]() Coherent phonon detection allows resolution in time of wavepacket dynamics that is otherwise averaged-out in standard Raman scattering. ![]() ![]() Time-domain observation of phonon dynamics has much lower sensitivity with respect to conventional Raman, but it enables direct measurement of excited-state dynamics, vibrational dephasing and mode coupling in a distinct way 15, 16. Quantum-chemical modelling 13 shows that this effect is due to a corrugation of the SWNT surface on photoexcitation, leading to a coupling between longitudinal and radial vibrations.Įlectron–phonon coupling in SWNTs is usually studied using Raman spectroscopy this technique is useful for investigating ground-state vibrations 14, whereas photoexcited-state vibrational dynamics remain largely unknown because, in the frequency domain, phonon replicas are hardly detectable in the presence of substantial inhomogeneous broadening. We observe vibrational wavepackets for the radial breathing mode (RBM) and the G mode, and in particular their anharmonic coupling, resulting in a frequency modulation of the G mode by the RBM. Here we report on the use of resonant sub-10-fs visible pulses 12 to generate and detect, in the time domain, coherent phonons in SWNT ensembles. In semiconducting SWNTs, medium-sized excitons (3–5 nm) with large binding energy and oscillator strength are the fundamental excitations 4, 5, 6, 7, 8 exciton wavefunction localization and one-dimensionality give rise to a strong electron–phonon coupling 9, 10, 11, the study of which is crucial for the understanding of their electronic and optical properties. Single-walled carbon nanotubes (SWNTs) are π-conjugated, quasi-one-dimensional structures consisting of rolled-up graphene sheets that, depending on their chirality, behave as semiconductors or metals 1 owing to their unique properties, they enable groundbreaking applications in mechanics, nanoelectronics and photonics 2, 3. ![]()
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