Mott metal-insulator transition in the doped Hubbard-Holstein model

Article

关键词: T-J MODEL;    FUNCTIONAL INTEGRAL APPROACH;    PHASE-SEPARATION;    ELECTRONIC-STRUCTURES;    GROUND-STATE;    MANGANITES;    ANTIFERROMAGNETISM;    SUPERCONDUCTIVITY;    MAGNETORESISTANCE;    THERMODYNAMICS;   

DOI  :  10.1103/PhysRevB.96.085132

来源: SCIE

【 摘 要 】

Motivated by the current interest in the understanding of the Mott insulators away from half-filling, observed in many perovskite oxides, we study the Mott metal-insulator transition in the doped Hubbard-Holstein model using the Hartree-Fock mean field theory. The Hubbard-Holstein model is the simplest model containing both the Coulomb and the electron-lattice interactions, which are important ingredients in the physics of the perovskite oxides. In contrast to the half-filled Hubbard model, which always results in a single phase (either metallic or insulating), our results show that away from half-filling, a mixed phase of metallic and insulating regions occurs. As the dopant concentration is increased, the metallic part progressively grows in volume, until it exceeds the percolation threshold, leading to percolative conduction. This happens above a critical dopant concentration delta(c), which, depending on the strength of the electron-lattice interaction, can be a significant fraction of unity. This means that the material could be insulating even for a substantial amount of doping, in contrast to the expectation that doped holes would destroy the insulating behavior of the half-filled Hubbard model. While effects of fluctuation beyond the mean field remain an open question, our results provide a starting point for the understanding of the density-driven metal-insulator transition observed in many complex oxides.

【 授权许可】

Free