Photoinduced Enhancement of Anisotropic Charge Correlations on Triangular Lattices with Trimers

TL;DR

This study uses theoretical models to show that photoexcitation can enhance anisotropic charge correlations in triangular lattice systems with trimers, potentially explaining experimental optical freezing phenomena.

Contribution

It reveals how photoinduced dynamics can selectively enhance anisotropic charge correlations in trimer-based triangular lattices, a novel insight into charge modulation mechanisms.

Findings

Photoexcitation enhances anisotropic charge correlations.

Effective on-site repulsion increases near certain trimer arrangements.

Results relate to optical freezing observed in experiments.

Abstract

To explore nontrivial photoinduced modulations of charge correlations, we theoretically study photoinduced dynamics in quarter-filled extended Hubbard models with competing intersite repulsive interactions on triangular lattices with trimers, where the end points are crystallographically equivalent. The exact diagonalization method is used and the time-dependent Schr\"odinger equation is numerically solved during and after photoexcitation. Time-averaged double occupancy and intersite density-density correlations can be interpreted as due to effective on-site and intersite repulsive interactions, respectively, relative to transfer energies. In the case where the intersite repulsive interactions compete with each other, the anisotropy of their effective interactions can be enhanced with the help of the trimers, irrespective of whether the trimers are linear or bent. In particular, in the case where the arrangement of the trimers is close to that in $\alpha$-(bis[ethylenedithio]-tetrathiafulvalene)$_2$I$_3$ [$\alpha$-(BEDT-TTF)$_2$I$_3$] in the metallic phase, the effective on-site repulsion is enhanced relative to the transfer energies. The relevance of this theoretical finding to the experimentally observed optical freezing of charge motion is discussed.