Large Modulations in the Intensity of Raman-Scattered Light from Pristine Carbon Nanotubes

Abstract

Large modulations of up to 2 orders of magnitude are observed in the Raman intensity of pristine, suspended, quasimetallic, single-walled carbon nanotubes in response to applied gate potentials. No change in the resonance condition is observed, and all Raman bands exhibit the same changes in intensity, regardless of phonon energy or laser excitation energy. The effect is not observed in semiconducting nanotubes. The electronic energy gaps correlate with the drop in the Raman intensity, and the recently observed Mott insulating behavior is suggested as a possible explanation for this effect.

Tunable electronic correlation effects in nanotube-light interactions

“…1(b)]. These investigations complement studies of gate-dependent Raman [13,14,27,28,41] and photoluminescence [13,37] spectroscopy of air-suspended nanotubes, gate-dependent Rayleigh scattering spectroscopy of individual nanotubes on substrates [52], and chemically-carrier-doped nanotubes [38,44,[47][48][49]51,53,57,61,62] showing spectral features attributed to formation of charged excitons (trions) [38]. We present all the Rayleigh spectra corrected for the ω 3 scattering efficiency factor to reflect directly the optical susceptibility.…”

“…Excitons in nanotubes are therefore highly stable at room temperature, unlike the case for conventional semiconductor quantum wires. Additionally, one can tune the carrier density and Fermi energy in nanotubes widely by means of electrostatic gating [10][11][12][13][14]. Nanotubes thus offer an ideal platform for the fundamental studies of the many-body interactions and their impact on the optical spectra of photoexcited quasi-1D systems [2][3][4][5][6][7][8][9].…”

Pronounced electron-phonon interactions in ultraclean suspended carbon nanotubes

“…However, the inclusion of a mini bandgap (120 meV) at T=150K in the band structure of the CNT, can reduce the renormalization of phonon energy, as shown in Figure 7(b). Small bandgaps of ~100meV ( ) have been observed experimentally in metallic nanotubes 2,7 , and have been attributed to the effect of curvature 22 and electron-electron interactions 2 . These calculations indicate that the experimental data shown in Figure 6(b) can be explained if a bandgap opens up in the metallic CNT as the temperature is lowered 7 .…”

“…Recently, the ability to fabricate ultra-clean, nearly defect-free, suspended single wall carbon nanotubes (SWNTs) has been developed [1][2][3] . This has allowed scientists to study many interesting physical phenomena such as negative differential conductance (NDC) 4 , breakdown of the BornOppenheimer approximation 5 , Wigner crystallization 6 , Raman intensity modulation 7 , and Mott insulator behavior 2,7 . Because of their one-dimensional nature, pristine, defect-free SWNTs provide an excellent experimental platform to study the exotic physical phenomena of onedimensional systems.…”

“…In this work, platinum source and drain electrodes are patterned on a Si/SiO 2 /Si 3 N 4 wafer, along with a platinum gate electrode in an 800nm deep, 2μm wide trench, as described previously 7,18 . A ferric nitrate catalyst for carbon nanotube growth is dispersed in de-ionized water and deposited in lithographically-defined windows patterned on the source and drain electrodes.…”