Photoinduced magnetic bound state in itinerant correlated electron system with spin-state degree of freedom

TL;DR

This paper investigates how photo-excitation induces a magnetic bound state in a correlated electron system with spin-state degrees of freedom, revealing a transition from low-spin to high-spin states via photo-doping and bound state formation.

Contribution

It introduces a theoretical framework for understanding photoinduced spin-state transitions and magnetic bound states in correlated electron systems with multiple orbitals.

Findings

Photo-excitation induces a transition from low-spin to high-spin states.

Formation of a ferromagnetic bound state stabilizes the high-spin state.

Time-dependent simulations suggest observable signatures in photoemission experiments.

Abstract

Photo-excited state in correlated electron system with spin-state degree of freedom is studied. We start from the two-orbital extended Hubbard model where energy difference between the two orbitals is introduced. Photo-excited metastable state is examined based on the effective model Hamiltonian derived by the two-orbital Hubbard model. Spin-state change is induced by photo-irradiation in the low-spin band insulator near the phase boundary. High-spin state is stabilized by creating a ferromagnetic bound state with photo-doped hole carriers. An optical absorption occurs between the bonding and antibonding orbitals inside of the bound state. Time-evolution for photo-excited states is simulated in the time-dependent mean-field scheme. Pair-annihilations of the photo-doped electron and hole generate the high-spin state in a low-spin band insulator. We propose that this process is directly observed by the time-resolved photoemission experiments.