# Photoexcitation of a polarization-inverted domain from the charge-ordered ferroelectric ground state of (TMTTF)$_{2}$PF$_{6}$

## TL;DR

This paper theoretically demonstrates that weak photoexcitation can invert electric polarization in a charge-ordered ferroelectric material, achieving a significant polarization change of about 36%, with implications for optical control of ferroelectric states.

## Contribution

It introduces a theoretical model showing how light can induce polarization inversion in (TMTTF)$_{2}$PF$_{6}$, revealing a large polarization change and connecting optical conductivity to photoinduced phase transitions.

## Key findings

- Weak photoexcitation achieves 18% charge transfer and polarization inversion.
- Photoexcitation results in a 36% change in electric polarization, larger than in typical organic materials.
- Single peak in optical conductivity correlates with polarization inversion at low temperature.

## Abstract

We theoretically revealed that a weak photoexcitation achieves the electric polarization-inversion with approximately $18\%$ of all the charges, which was interpreted as a superimposition of multi-exciton states, from the charge-ordered ferroelectric ground state of (TMTTF)$_{2}$PF$_{6}$ at absolute zero temperature. Regarding a relative change of electric polarization ($\Delta P/P$), the photoexcitation corresponds to $36\%$, which is much larger than $\Delta P/P$ of other typical organic materials. The value of $\Delta P/P\sim 36\%$ can be enlarged by a strong photoexcitation. This fact is useful not only for applications of this material and other analogous materials in optical devices but also for researches toward controlling electric polarizations by light, which is one of the recent attracting issues on photoinduced phase transition phenomena. The photoexcitation of $\Delta P/P\sim 36\%$ corresponds to the single peak of the optical conductivity in the low-energy region, which was also observed at 10 K. Theoretical calculations are based on a quarter-filled one-dimensional effective model with appropriate parameters and 50 unit cells.