Phase Transition in a One-Dimensional Extended Peierls-Hubbard Model with a Pulse of Oscillating Electric Field: II. Linear Behavior in Neutral-to-Ionic Transition

TL;DR

This study investigates the neutral-to-ionic phase transition in a one-dimensional extended Peierls-Hubbard model under an oscillating electric field, revealing linear energy dependence and uncooperative transition dynamics consistent with experimental observations.

Contribution

It demonstrates that the neutral-to-ionic transition proceeds linearly with energy input and remains uncooperative, contrasting with previous ionic-to-neutral studies, and explores the role of electron-lattice coupling.

Findings

Final ionicity is linearly related to energy increment.

Electric field at the absorption peak most effectively induces transition.

Transition remains uncooperative with limited domain proliferation.

Abstract

Dynamics of charge density and lattice displacements after the neutral phase is photoexcited is studied by solving the time-dependent Schr\"odinger equation for a one-dimensional extended Peierls-Hubbard model with alternating potentials. In contrast to the ionic-to-neutral transition studied previously, the neutral-to-ionic transition proceeds in an uncooperative manner as far as the one-dimensional system is concerned. The final ionicity is a linear function of the increment of the total energy. After the electric field is turned off, the electronic state does not significantly change, roughly keeping the ionicity, even if the transition is not completed, because the ionic domains never proliferate. As a consequence, an electric field with frequency just at the linear absorption peak causes the neutral-to-ionic transition the most efficiently. These findings are consistent with the recent experiments on the mixed-stack organic charge-transfer complex, TTF-CA. We artificially modify or remove the electron-lattice coupling to discuss the origin of such differences between the two transitions.