Unconventional slowing down of electronic recovery in photoexcited charge-ordered La$_{1/3}$Sr$_{2/3}$FeO$_3$

TL;DR

This study reveals an unusual, long-lasting slowdown in the recovery of charge order in La$_{1/3}$Sr$_{2/3}$FeO$_3$ after photoexcitation, driven by magnetic interactions near a weakly first-order phase transition, beyond thermal relaxation times.

Contribution

It uncovers pseudo-critical electronic dynamics influenced by magnetic interactions in a charge-ordered system, extending understanding of phase recovery beyond thermal processes.

Findings

Recovery time increases by orders of magnitude near phase transition temperature.

Electronic recovery is governed by magnetic interactions, not just thermal relaxation.

Long electronic recovery times are observed beyond lattice cooling times.

Abstract

Ordered electronic phases are intimately related to emerging phenomena such as high Tc superconductivity and colossal magnetoresistance. The coupling of electronic charge with other degrees of freedom such as lattice and spin are of central interest in correlated systems. Their correlations have been intensively studied from femtosecond to picosecond time scales, while the dynamics of ordered electronic phases beyond nanoseconds are usually assumed to follow a trivia thermally driven recovery. Here, we report an unusual slowing down of the recovery of an electronic phase across a first-order phase transition, far beyond thermal relaxation time. Following optical excitation, the recovery time of both transient optical reflectivity and x-ray diffraction intensity from a charge-ordered superstructure in a La$_{1/3}$Sr$_{2/3}$FeO$_3$ thin film increases by orders of magnitude longer than the independently measured lattice cooling time when the sample temperature approaches the phase transition temperature. The combined experimental and theoretical investigations show that the slowing down of electronic recovery corresponds to the pseudo-critical dynamics that originates from magnetic interactions close to a weakly first-order phase transition. This extraordinary long electronic recovery time exemplifies an interplay of ordered electronic phases with magnetism beyond thermal processes in correlated systems.