Photoinduced melting of charge order in a quarter-filled electron system coupled with different types of phonons

TL;DR

This study investigates how photoexcitation can melt charge order in a one-dimensional quarter-filled Hubbard model with electron-phonon interactions, revealing the roles of different phonons and excitation energies in the process.

Contribution

It provides a detailed analysis of photoinduced charge dynamics considering both bond- and charge-coupled phonons, using exact many-electron wave functions and adiabatic potentials.

Findings

Different photoexcitation pathways lead to distinct charge dynamics.

Adiabatic potentials help explain the efficiency of charge order melting.

Relative phonon frequencies influence the photoinduced melting process.

Abstract

Photoinduced melting of charge order is calculated by using the exact many-electron wave function coupled with classically treated phonons in the one-dimensional quarter-filled Hubbard model with Peierls and Holstein types of electron-phonon couplings. The model parameters are taken from recent experiments on (EDO-TTF)_2PF_6 (EDO-TTF=ethylenedioxy-tetrathiafulvalene) with (0110) charge order, where transfer integrals are modulated by molecular displacements (bond-coupled phonons) and site energies by molecular deformations (charge-coupled phonons). The charge-transfer photoexcitation from (0110) to (0200) configurations and that from (0110) to (1010) configurations have different energies. The corresponding excited states have different shapes of adiabatic potentials as a function of these two phonon amplitudes. The adiabatic potentials are shown to be useful in understanding differences in the photoinduced charge dynamics and the efficiency of melting, which depend not only on the excitation energy but also on the relative phonon frequency of the bond- and charge-coupled phonons.