Photoinduced melting dynamics and collective mode in a correlated charge-ordered system

Abstract

We theoretically investigate the transient spectral function during the photoinduced melting of charge order in a correlated electron system, to unravel the dynamical processes triggered by different initial excitations. We employ a one-dimensional interacting spinless fermion model introducing a pulsed laser light, and perform a comparative study by the Hartree-Fock approximation and by the exact diagonalization method to numerically solve the time-dependent Schrödinger equation. We find characteristic behavior in the transient spectral function, whose features strongly depend on the pump light frequency $\ddot{I}{‰}_p$. When $\ddot{I}{‰}_p$ is resonant with the collective phase mode of frequency $\hat{I}{\text{c◯}}_c\simeq \hat{I}{”}_{\mathrm{CO}}/2$, where $\hat{I}{”}_{\mathrm{CO}}$ is the charge gap, the transient spectral function exhibits a photoinduced in-gap weight which triggers large responses. With increasing the laser intensity, the development of in-gap weight directly turns into the collapse of the gap. This charge-order destabilization process is in sharp contrast to the case of $\ddot{I}{‰}_p>\hat{I}{”}_{\mathrm{CO}}$, where the photoirradiation induces interband electron-hole excitations giving rise to a shrinkage of the gap. The impact of quantum fluctuations and spatial inhomogeneity on the photoinduced dynamics is also discussed.

10 pages, 12 figures, to be published in Phys. Rev. B