Energy of K-momentum dark excitons in carbon nanotubes by optical spectroscopy.

Phonon sideband optical spectroscopy determines the energy of the dark K-momentum exciton for (6,5) carbon nanotubes. One-phonon sidebands appear in absorption and emission, split by two zone-boundary (K-point) phonons. Their average energy locates the E11 K-momentum exciton 36 meV above the E11 bright level, higher than available theoretical estimates. A model for exciton-phonon coupling shows the absorbance sideband depends sensitively on the K-momentum exciton effective mass and has minimal contributions from zone-center phonons, which dominate the Raman spectra of carbon nanotubes.

Photoluminescence from intertube carrier migration in single-walled carbon nanotube bundles.

Photoluminescence (PL) identifies spectroscopic signatures of intertube transfer of optically pumped carriers in single-walled carbon nanotube (SWNT) ensembles. Resonant photoexcitation of large band gap SWNTs produces strong PL from smaller band gap SWNTs. Magnetic alignment measurements associate the energy-transfer PL peaks with the formation of SWNT bundles, suggesting that efficient coupling results from physical contact.

Dynamic Kerr effect and the spectral weight transfer of the manganites.

Pump-probe Kerr spectroscopy uncovers surface magnetic dynamics in Pr0.67Ca0.33MnO3 that are undetected by established methods based on optical spectral weight transfer. The connection between spin and charge dynamics in the colossally magnetoresistive manganites may thus be weaker than previously thought. Important differences from conventional ferromagnetic metals manifest as long-lived, magneto-optical coupling transients, which may be generic to all manganites.