On the Magnetic and Metal-Insulator Transitions in a Two-Dimensional Hubbard Model

概要

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Antiferrotaaagnetic and taaetal to instrlator tr?tnsitions in the ground state of two-dimensionalhalf'-filled and nearly half'-filled Htrbbard ttaodels with the nearest neighbor and the second nearestneighbor transfers ( -t and t', respectively) are sttrdied by tusing the Green ' s ['trnction approachwitla the self'-energy Lip to the secotad order in the cotrpling constant U. For a choice of theparautaeter valtre t' /t : 0.2 flue harlf'-filled taaodel trndergoes the first order phase transition betweenparaznagnetic tnetallic (PIlN'I) ph?xse and stntif'erroraaagnetic insulator (AFT) phase at U/t : 4.0while the first order tratnsitiota betxveen PKI and antif'erronaatgnetic taaetallic (AFIVI) phases takesplace for nearly half'-filled band. The one-electron spectral density is calctrlated f'or the PIVI,AFllxzI, and AFT pharses ne?tr the phase botrndaries, In the PIVI phase the quasi-particle dispersionindicates the band narrowing ['IOlTl the Hartree-Fock results and the flat band behavior as wasindicated by previotrs stadies and XV2lS observed in high-'Z'. ctrprates. The quasi-particle dispersionin the AFIVI phase is seen to be close to the Hsrrtree-Fock restrlts.
社団法人日本物理学会の論文
1998-01-15