# High-Frequency Analysis of Effective Interactions and Bandwidth for Transient States after Monocycle Pulse Excitation of Extended Hubbard Model

## TL;DR

This paper investigates how high-frequency periodic driving influences effective interactions and bandwidth in extended Hubbard models, and how these effects manifest in correlation functions after monocycle pulse excitation, with implications for experimental observations.

## Contribution

It introduces a high-frequency expansion method for arbitrary density-density interactions and analyzes the resulting effects on correlation functions in a specific lattice model.

## Key findings

- Effective interactions depend on the polarization of the driving field.
- Correlation functions after excitation align with the derived effective interactions.
- Photoinduced charge correlation enhancement cannot be fully explained by effective interactions or bandwidth.

## Abstract

Using a high-frequency expansion in periodically driven extended Hubbard models, where the strengths and ranges of density-density interactions are arbitrary, we obtain the effective interactions and bandwidth, which depend sensitively on the polarization of the driving field. Then, we numerically calculate modulations of correlation functions in a quarter-filled extended Hubbard model with nearest-neighbor interactions on a triangular lattice with trimers after monocycle pulse excitation. We discuss how the resultant modulations are compatible with the effective interactions and bandwidth derived above on the basis of their dependence on the polarization of photoexcitation, which is easily accessible by experiments. Some correlation functions after monocycle pulse excitation are consistent with the effective interactions, which are weaker or stronger than the original ones. However, the photoinduced enhancement of anisotropic charge correlations previously discussed for the three-quarter-filled organic conductor $\alpha$-(bis[ethylenedithio]-tetrathiafulvalene)$_2$I$_3$ [$\alpha$-(BEDT-TTF)$_2$I$_3$] in the metallic phase is not fully explained by the effective interactions or bandwidth, which are derived independently of the filling.