A Variational Improvement of the Hartree-Fock Approach to the 2D Hubbard Model
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arXiv
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| Autores principales: | , |
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| Formato: | Preprint |
| Publicado: |
2024
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| _version_ | 1866909243911700480 |
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| author | Matsuyama, Kazue Greensite, Jeff |
| author_facet | Matsuyama, Kazue Greensite, Jeff |
| contents | We consider a refinement of the usual Hartree-Fock method applied to the 2D Hubbard model, in Nambu spinor formulation. The new element is the addition of a "condensate inducing" term proportional to a variational parameter h to the Hartree-Fock Hamiltonian, which generates an s- or d-wave condensate at zero temperature. This modified Hartree-Fock Hamiltonian is used only to generate variational trial states; energy expectation values are computed in the full two-dimensional Hubbard Hamiltonian with no modification. It is found that there exist trial states with non-vanishing condensates which are lower in energy than the standard Hartree-Fock ground states. However, these lower energy condensate states exist only in a spatially inhomogeneous (stripe) phase. No lowering of energy, relative to the Hartree-Fock ground state, is found in the spatially homogenous region of the U-density phase plane. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2404_04777 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | A Variational Improvement of the Hartree-Fock Approach to the 2D Hubbard Model Matsuyama, Kazue Greensite, Jeff Strongly Correlated Electrons Superconductivity We consider a refinement of the usual Hartree-Fock method applied to the 2D Hubbard model, in Nambu spinor formulation. The new element is the addition of a "condensate inducing" term proportional to a variational parameter h to the Hartree-Fock Hamiltonian, which generates an s- or d-wave condensate at zero temperature. This modified Hartree-Fock Hamiltonian is used only to generate variational trial states; energy expectation values are computed in the full two-dimensional Hubbard Hamiltonian with no modification. It is found that there exist trial states with non-vanishing condensates which are lower in energy than the standard Hartree-Fock ground states. However, these lower energy condensate states exist only in a spatially inhomogeneous (stripe) phase. No lowering of energy, relative to the Hartree-Fock ground state, is found in the spatially homogenous region of the U-density phase plane. |
| title | A Variational Improvement of the Hartree-Fock Approach to the 2D Hubbard Model |
| topic | Strongly Correlated Electrons Superconductivity |
| url | https://arxiv.org/abs/2404.04777 |