Eur. Phys. J. B 72, 59-66 (2009)
https://doi.org/10.1140/epjb/e2009-00314-1

Two-orbital systems with crystal field splitting and interorbital hopping

¹ Department of Physics, Beijing Normal University, 100875, Beijing, P.R. China
² Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P.O. Box 1129, Hefei, 230031, P.R. China

Corresponding author: ^a yunsong@bnu.edu.cn

Received: 25 January 2009
Revised: 20 July 2009
Published online: 26 September 2009

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-xSr_xRuO₄. 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-xSr_xRuO₄, we demonstrate that in the doping region from x=0.2 to 2.0, the negative level splitting is unfavorable to the OSMT phase.