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Charge gap in the one-dimensional extended Hubbard model at quarter filling Charge gap in the one-dimensional extended Hubbard model at quarter filling Sano, K. Ono, Y. Copyright (C) 2007 The American Physical Society We propose a different combined approach, which consists of the exact diagonalization, renormalization group, and Bethe ansatz methods, for precise estimates of the charge gap Δ in the one-dimensional extended Hubbard model, with on-site and nearest-neighbor interactions U and V at quarter filling. This approach enables us to obtain the absolute value of Δ, including the prefactor, without ambiguity even in the critical regime of the metal-insulator transition (MIT) where Δ is exponentially small, beyond usual renormalization group methods and/or finite-size scaling approaches. The detailed results of Δ, down to the order of 10−10 near the MIT, are shown as contour lines on the U-V plane. American Physical Society 2007-03 eng journal article http://hdl.handle.net/10191/26869 https://niigata-u.repo.nii.ac.jp/records/2503 info:doi/10.1103/PhysRevB.75.113103 http://journals.aps.org/prb/pdf/10.1103/PhysRevB.75.113103 AA11187113 10980121 Physical review. Third series. B, Condensed matter and materials physics Physical review. Third series. B, Condensed matter and materials physics 75 113103-1 113103-4 https://niigata-u.repo.nii.ac.jp/record/2503/files/75_113103.pdf application/pdf 89.0 kB 2019-07-29