Photoinduced Nonequilibrium Dynamics in Charge Ordered Materials

TL;DR

This paper investigates the complex nonequilibrium dynamics of photoinduced phase transitions in charge ordered materials, highlighting the interplay of electrons, lattice distortions, and thermal effects through simulations.

Contribution

It introduces a detailed simulation approach combining tight-binding and Boltzmann equations to analyze charge order melting and lattice dynamics under photoexcitation.

Findings

Partially decoupled oscillations of electronic and lattice order parameters.

Energy-efficient CO melting at lower photon energies.

Cooling rate decreases significantly when the CO gap reopens.

Abstract

We study the nonequilibrium dynamics of photoinduced phase transitions in charge ordered (CO) systems with a strong electron-lattice interaction and analyze the interplay between electrons, periodic lattice distortions, and a phonon thermal reservoir. Simulations based on a tight-binding Hamiltonian and Boltzmann equations reveal partially decoupled oscillations of the electronic order parameter and the periodic lattice distortion during CO melting, which becomes more energy efficient with lower photon energy. The cooling rate of the electron system correlates with the CO gap dynamics, responsible for an order of magnitude decrease in the cooling rate upon the gap reopening. We also find that the time-dependent frequency of coherent oscillation reflects the dynamics of the energy landscape, such as transition between single-well and double-well, which sensitively depends on the photon energy and the pump fluence. The results demonstrate the intricate nonequilibrium dynamics in CO materials.