Excitation of a breather mode of bound soliton pairs in trans-polyacetylene by sub-five-femtosecond optical pulses -: art. no. 027401

Trans-polyacetylene with a degenerate ground state has a nonlinear excitation of soliton after photoexcitation, due to the electron-phonon coupling. The excess energy of an excited electron-hole pair over a soliton pair creation induces a breather oscillation characterized by collective stretching vibration of the carbon-carbon bonds. A time-frequency analysis of pump probe signal shows that instantaneous frequencies of stretching modes are modulated for similar to50 fs after excitation and the modulation period is 44 +/- 3 fs consistent with the theoretical expectation, clearly verifying the breather.