Charge ordered insulator without magnetic order studied by correlator projection method

• Published in: Journal of the Physical Society of Japan 2005-10, Vol.74 (10), p.2769-2782
• Main Authors: HANASAKI, Kota, IMADA, Masatoshi
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron states; Exact sciences and technology; Metal-insulator transitions and other electronic transitions; Physics; Theories and models of many electron systems
• ISSN: 0031-9015; 1347-4073
• DOI: 10.1143/jpsj.74.2769

The Hubbard model with additional intersite interaction 'V' (the extended Hubbard model) is investigated by the correlator projection method (CPM). CPM is a newly developed numerical method that combines the equation-of-motion approach and the dynamical mean-field theory. Using this method, properties of the extended Hubbard Model at quarter filling are discussed with special emphasis on the metal-insulator transition induced by electron-electron correlations. As we increase the interaction, a metal-insulator transition to a charge ordered insulator with antiferromagnetic order occurs at low temperatures, but a metal-insulator transition to a charge ordered insulator without magnetic symmetry breaking occurs at intermediate temperatures. Here, the magnetic order is found to be confined to low temperatures because of the smallness of the exchange coupling Jeff. The present results are in sharp contrast to the Hatree-Fock approximation whereas they are in agreement with the experimental results on quarter-filled materials with strong correlations such as organic BEDT-TTF conductors.