The observation of strong dynamic electron-phonon couplings due to a breather state in trans-polyacetylene

Abstract

The dynamics preceding the separation process of a charged soliton pair after photoexcitation in trans-polyacetylene was successfully time-resolved using ultrafast spectroscopy with a few-optical-cycle laser. It was directly verified that after photoexcitation, the electron-hole pair relaxes with a breather mode as theory predicts with an electron-hole pair lifetime of 33-50 fs, which is in agreement with the electronic dephasing time. By applying the spectrogram analysis to the time trace of the absorbance change, the ultrafast amplitude and frequency modulations of C-C and C=C stretching modes lasting only shorter than 100 fs induced by breather modes can be observed simultaneously for the first time. The frequency shift of C-C and C=C stretching modes caused by the breather mode are observed in good agreement with the SSH Hamiltonian. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim