  Transient quantum dynamics in an interacting fermion-phonon system are
investigated. In particular, a charge order (CO) melting after a short
optical-pulse irradiation and roles of the quantum phonons on the transient
dynamics are focused on. A spinless-fermion model in a one-dimensional chain
coupled with local phonons is analyzed numerically. The infinite time-evolving
block decimation algorithm is adopted as a reliable numerical method for
one-dimensional quantum many-body systems. Numerical results for the
photoinduced CO melting dynamics without phonons are well interpreted by the
soliton picture for the CO domains. This interpretation is confirmed by the
numerical simulation for an artificial local excitation and the classical
soliton model. In the case of the large phonon frequency corresponding to the
antiadiabatic condition, the CO melting is induced by propagations of the
polaronic solitons with the renormalized soliton velocity. On the other hand,
in the case of the small phonon frequency corresponding to the adiabatic
condition, the first stage of the CO melting dynamics occurs due to the energy
transfer from the fermionic to phononic systems, and the second stage is
brought about by the soliton motions around the bottom of the soliton band.
Present analyses provide a standard reference for the photoinduced CO melting
dynamics in low-dimensional many-body quantum systems.
