Relaxation of photoexcitations in polaron-induced magnetic microstructures

TL;DR

This study models photoexcitation dynamics in a manganite system, revealing how magnetic microstructures like Zener polarons significantly slow relaxation processes, with implications for understanding correlated electron materials.

Contribution

It introduces a combined approach using coarse-grained polaron modeling and tDMRG to analyze photoexcitation relaxation in a complex correlated system.

Findings

Magnetic microstructures extend relaxation times of photoexcitations.

Zener polarons form antiferromagnetic patterns at half-doping.

Relaxation dynamics are influenced by quasiparticle behavior and microstructure.

Abstract

We investigate the evolution of a photoexcitation in correlated materials over a wide range of time scales. The system studied is a one-dimensional model of a manganite with correlated electron, spin, orbital, and lattice degrees of freedom, which we relate to the three-dimensional material Pr$_{1-x}$Ca$_{x}$MnO$_3$. The ground-state phases for the entire composition range are determined and rationalized by a coarse-grained polaron model. At half-doping a pattern of antiferromagnetically coupled Zener polarons is realized. Using time-dependent density-matrix renormalization group (tDMRG), we treat the electronic quantum dynamics following the excitation. The emergence of quasiparticles is addressed, and the relaxation of the nonequilibrium quasiparticle distribution is investigated via a linearized quantum-Boltzmann equation. Our approach shows that the magnetic microstructure caused by the Zener polarons leads to an increase of the relaxation times of the excitation.