Effect of Spin Correlations on Multi-orbital Metal-Insulator Transitions and Suppression of Orbital Selective Mott Transitions

TL;DR

This paper investigates how spin correlations influence metal-insulator transitions in two-orbital Hubbard models, revealing suppression of orbital selective Mott transitions and complex spin-driven phases.

Contribution

It demonstrates the significant impact of spin correlations on MITs and the suppression of orbital selective Mott transitions in multi-orbital systems.

Findings

Simultaneous MIT in both orbitals with Coulomb increase at half-filling.

Suppression of orbital selective Mott transition in paramagnetic state.

Crossover from spin-gapped to fully-polarized Mott insulator in strong correlations.

Abstract

We present the influence of spin correlation on the metal-insulator transitions (MIT) in two-orbital Hubbard models by the Kotliar-Ruckenstein slave-boson approach. In the asymmetric half-filling situation, the two orbits simultaneously transit from conducting to insulating states with the increase of Coulomb correlation, accompanied by a paramagnetic (PM)-antiferromagnetic (AFM) transition. The orbital selective Mott transition found in the PM condition is completely suppressed over a wide correlation range, though it may exist in the systems away from half-filling. In the insulating state, the system crosses over from a partially-polarized spin-gapped phase in the intermediate correlation regime to an almost fully-polarized Mott insulating phase in the strong correlation regime. These results demonstrate that the spin modulation to the quasiparticle spectra brings much rich and more interesting MIT scenario in multi-orbital correlated systems.