title: Selective Excitation of Atomic-Scale Dynamics by Coherent Exciton Motion in the Non-Born-Oppenheimer Regime.
abstract: 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, phase-coherent excitation of the two lowest electronic transitions in semiconducting single-walled 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.
authors: †Division of Chemistry and Biological Chemistry, and Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 631371, Singapore.
authors: Zhaogang
authors: Z
authors: Nie
authors: ‡Department of Chemistry, University of Rochester, RC Box 270216, Rochester, New York 14627, United States.|§School of Physics, Complex Adaptive Systems Laboratory, University College Dublin, Belfield, Dublin 4, Ireland.
authors: Run
authors: R
authors: Long
authors: †Division of Chemistry and Biological Chemistry, and Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 631371, Singapore.
authors: Jialin
authors: J
authors: Li
authors: †Division of Chemistry and Biological Chemistry, and Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 631371, Singapore.
authors: Yi Ying
authors: YY
authors: Zheng
authors: ‡Department of Chemistry, University of Rochester, RC Box 270216, Rochester, New York 14627, United States.
authors: Oleg V
authors: OV
authors: Prezhdo
authors: †Division of Chemistry and Biological Chemistry, and Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 631371, Singapore.
authors: Zhi-Heng
authors: ZH
authors: Loh
keywords: coherent phonon; femtosecond spectroscopy; nonadiabatic dynamics; single-walled carbon nanotubes; valence electron motion