Two-orbital Systems with Crystal Field Splitting and Interorbital Hopping

TL;DR

This study uses dynamical mean-field theory to explore how crystal field splitting and interorbital hopping influence the orbital selective Mott transition in a two-orbital Hubbard model, with implications for the compound Ca$_{2-x}$Sr$_{x}$RuO$_{4}$.

Contribution

It reveals how interorbital hopping and level splitting affect the OSMT regime, providing insights into the electronic behavior of related materials.

Findings

OSMT phase shows distinct optical conductivity features.

Interorbital hopping expands the OSMT regime.

Negative level splitting suppresses the OSMT phase.

Abstract

The nondegenerate two-orbital Hubbard model is studied within the dynamic mean-field theory to reveal the influence of two important factors, i.e. crystal field splitting and interorbital hopping, on orbital selective Mott transition (OSMT) and realistic compound Ca$_{2-x}$Sr$_{x}$RuO$_{4}$. A distinctive feature of the optical conductivity of the two nondegenerate bands is found in OSMT phase, where the metallic character of the wide band is indicated by a nonzero Drude peak, while the insulating narrow band has its Drude peak drop to zero in the mean time. We also find that the OSMT regime expands profoundly with the increase of interorbital hopping integrals. On the contrary, it is shown that large and negative level splitting of the two orbitals diminishes the OSMT regime completely. Applying the present findings to compound Ca$_{2-x}$Sr$_{x}$RuO$_{4}$, we demonstrate that in the doping region from $x=0.2$ to 2.0, the negative level splitting is unfavorable to the OSMT phase.