Growth Dynamics of Photoinduced Domains in Two-Dimensional Charge-Ordered Conductors Depending on Stabilization Mechanisms

TL;DR

This study theoretically investigates how photoinduced melting of charge orders varies in organic conductors, revealing stabilization mechanisms influence domain growth anisotropy and energy requirements, aligning with recent experimental observations.

Contribution

It provides a comparative analysis of stabilization effects on photoinduced domain dynamics in two different charge-ordered organic conductors using numerical simulations.

Findings

Higher energy needed to melt charge order in heta-(BEDT-TTF)2RbZn(SCN)4 due to larger stabilization energy.

Domain growth is anisotropic in heta-(BEDT-TTF)2RbZn(SCN)4, limited perpendicular to stripes.

In eta-(BEDT-TTF)2I3, domains expand more freely due to local lattice distortions stabilizing charge order.

Abstract

Photoinduced melting of horizontal-stripe charge orders in quasi-two-dimensional organic conductors \theta-(BEDT-TTF)2RbZn(SCN)4[BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene] and \alpha-(BEDT-TTF)2I3 is investigated theoretically. By numerically solving the time-dependent Schr\"odinger equation, we study the photoinduced dynamics in extended Peierls-Hubbard models on anisotropic triangular lattices within the Hartree-Fock approximation. The melting of the charge order needs more energy for \theta-(BEDT-TTF)2RbZn(SCN)4 than for \alpha-(BEDT-TTF)2I3, which is a consequence of the larger stabilization energy in \theta-(BEDT-TTF)2RbZn(SCN)4. After local photoexcitation in the charge ordered states, the growth of a photoinduced domain shows anisotropy. In \theta-(BEDT-TTF)2RbZn(SCN)4, the domain hardly expands to the direction perpendicular to the horizontal-stripes. This is because all the molecules on the hole-rich stripe are rotated in one direction and those on the hole-poor stripe in the other direction. They modulate horizontally connected transfer integrals homogeneously, stabilizing the charge order stripe by stripe. In \alpha-(BEDT-TTF)2I3, lattice distortions locally stabilize the charge order so that it is easily weakened by local photoexcitation. The photoinduced domain indeed expands in the plane. These results are consistent with recent observation by femtosecond reflection spectroscopy.