Ultrafast Photoinduced Formation of Metallic State in a Perovskite-type Manganite with Short Range Charge and Orbital Order

TL;DR

This study demonstrates that femtosecond photoirradiation induces an ultrafast transition from a charge-ordered insulating state to a metallic ferromagnetic state in a perovskite manganite, revealing rapid electronic and magnetic dynamics.

Contribution

The paper provides direct evidence of a sub-200 femtosecond transition from charge/orbital order to a metallic ferromagnetic state induced by ultrafast photoirradiation in a manganite.

Findings

Immediate increase in mid-infrared reflectivity after photoirradiation.

Optical conductivity indicates formation of a metallic state.

Ferromagnetic spin arrangements form within 200 fs via double exchange.

Abstract

Femtosecond reflection spectroscopy was performed on a perovskite-type manganite, Gd0.55Sr0.45MnO3, with the short-range charge and orbital order (CO/OO). Immediately after the photoirradiation, a large increase of the reflectivity was detected in the mid-infrared region. The optical conductivity spectrum under photoirradiation obtained from the Kramers-Kronig analyses of the reflectivity changes demonstrates a formation of a metallic state. This suggests that ferromagnetic spin arrangements occur within the time resolution (ca. 200 fs) through the double exchange interaction, resulting in an ultrafast CO/OO to FM switching.