Spin-state transition and phase separation in multi-orbital Hubbard model

TL;DR

This paper investigates spin-state transitions and phase separation in a multi-orbital Hubbard model, revealing how orbital energy differences and Hund coupling influence electronic and magnetic phases.

Contribution

It introduces a variational Monte-Carlo approach to analyze spin-state transitions and phase separation in multi-orbital systems, highlighting the role of band width differences.

Findings

Electronic phase separation occurs between low-spin insulator and high-spin metal.

Orbital band width differences are crucial for spin-state transition.

Spin states can be controlled by orbital energy separation and Hund coupling.

Abstract

We study spin-state transition and phase separation involving this transition based on the milti-orbital Hubbard model. Multiple spin states are realized by changing the energy separation between the two orbitals and the on-site Hund coupling. By utilizing the variational Monte-Carlo simulation, we analyze the electronic and magnetic structures in hole doped and undoped states. Electronic phase separation occurs between the low-spin band insulating state and the high-spin ferromagnetic metallic one. Difference of the band widths in the two orbitals is of prime importance for the spin-state transition and the phase separation.