Selective excitation of atomic-scale dynamics by coherent exciton motion in the non-born–Oppenheimer regime.
Zheng, Yi Ying.
Prezhdo, Oleg V.
Date of Issue2013
School of Physical and Mathematical Sciences
Time-domain investigations of the nonadiabatic coupling between electronic and vibrational degrees of freedom have focused primarily on the formation of electronic superpositions induced by atomic motion. The effect of electronic nonstationary-state dynamics on atomic motion remains unexplored. Here, phasecoherent excitation of the two lowest electronic transitions in semiconducting singlewalled carbon nanotubes by broadband <5-fs pulses directly triggers coherent exciton motion along the axis of the nanotubes. Optical pump−probe spectroscopy with sub-10-fs time resolution reveals that exciton motion selectively excites the high-frequency G mode coherent phonon, in good agreement with results obtained from time-domain ab initio simulations. This observed phenomenon arises from the direct modulation of the C−C interatomic potential by coherent exciton motion on a time scale that is commensurate with atomic motion. Our results suggest the possibility of employing light-field manipulation of electron densities in the non-Born−Oppenheimer regime to initiate selective atomic motion.
The journal of physical chemistry letters
© 2013 American Chemical Society. This is the author created version of a work that has been peer reviewed and accepted for publication by The Journal of Physical Chemistry Letters, American Chemical Society. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [http://dx.doi.org/10.1021/jz401945m].