Photo-induced spin-state change in itinerant correlated-electron system

TL;DR

This paper investigates how light can induce a transition from low-spin to high-spin states in a correlated-electron system, explaining experimental optical spectra through a theoretical model.

Contribution

It develops a theoretical framework based on the two-orbital Hubbard model to describe photo-induced spin-state changes in itinerant correlated-electron systems.

Findings

Photo-induced high-spin state forms a bound state with a photoexcited hole.

Characteristic peaks appear in optical absorption spectra after photo-excitation.

The model explains recent ultrafast optical spectroscopy experiments in cobaltites.

Abstract

Photo-induced spin-state change in itinerant correlated-electron system is studied. The model Hamiltonians before and after photon-pumping are derived from the two-orbital Hubbard model with crystalline field splitting. A photon introduced in the low-spin band insulator induces a bound state of the high-spin state and a photoexcited hole. This bound state brings a characteristic peak in the optical absorption spectra in the photo-excited state. The resent results well explain the recent experimental results of the ultrafast optical spectroscopy in perovskite cobaltites.