Abstract
By applying dynamical mean-field theory in combination with exact diagonalization at zero temperature to a half-filled Hubbard model with two orbitals having distinct noninteracting densities of states, we show that an orbital selective Mott transition (OSMT), where part of correlated itinerant electrons become localized, will take place even if the crystal field splitting, the differences in bandwidth, and orbital degeneracy are all absent. We find that not only decoupling of charge degrees of freedom between different orbitals, but also formation of local spin triplets are crucial for the appearance of such an OSMT. The relevance of our findings to the iron-based superconductors and Ca2−xSrxRuO4 is discussed, and a reasonable candidate to detect such an OSMT is proposed.
Highlights
Since unconventional superconductivity emerges in the proximity to the Mott metal-to-insulator transition[1,2], it is of great importance to understand the origin for the Mott physics
By applying dynamical mean-field theory in combination with exact diagonalization at zero temperature to a half-filled Hubbard model with two orbitals having distinct noninteracting densities of states, we show that an orbital selective Mott transition (OSMT) will take place even without crystal field splitting, differences in bandwidth and orbital degeneracy
We find that formation of local spin triplet states followed by a two-stage breakdown of the Kondo effect, rather than decoupling of charge degrees of freedom among different orbitals, is the underlying physics for the OSMT
Summary
Since unconventional superconductivity emerges in the proximity to the Mott metal-to-insulator transition[1,2], it is of great importance to understand the origin for the Mott physics. In single orbital cases, enhanced spin fluctuations by strong correlations win the competition against kinetic energy, leading to a complete localization of all electrons across the Mott transition[1] Such a simple origin can hardly be applied to various topical materials directly, such as iron-based superconductors[3,4], Ca2−xSrxRuO45, and 3He bilayer system[6], where localized and itinerant fermions coexist. 1) large difference in bandwidth is not present either in Ca2−xSrxRuO431,32 or in iron-based superconductors33; 2) crystal field splitting may lead to a single metal-toinsulator transition in Ca2−xSrxRuO434; and 3) the orbital degeneracy may be lifted if lattice distortion occurs in the iron-based superconductors[35]. IV we discuss the relevance of our findings to the materials and present a summary
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