Hubbard interaction and competing approximations
Research context
postgraduate concept · conditional · As of 2026-10-10
A single-band Hubbard model combines hopping t_ij with on-site repulsion U n_i↑n_i↓.
Key knowledge
A single-band Hubbard model combines hopping t_ij with on-site repulsion U n_i↑n_i↓. At half filling and large U/t, virtual hopping in a simple nearest-neighbour model produces antiferromagnetic exchange J≈4t²/U. The model isolates correlations; a material's orbitals, long-range interactions and lattice geometry can demand a different Hamiltonian.
Values and equations
H=−Σ_ijσt_ij c_iσ†c_jσ+UΣ_i n_i↑n_i↓; J≈4t²/U
- H,t_ij,U,J
- Hamiltonian and energy parameters J or eV consistently
- c_iσ,n_iσ
- Dimensionless lattice fermion and occupation operators
Conditions and scope
- Repulsive U>0, well-separated charge excitation scale and specified lattice/filling; the displayed exchange estimate assumes real spin-independent hopping t and is a strong-coupling expansion.
- Mean-field broken-symmetry, perturbative quasiparticle and impurity-based methods have different controllable limits; neither U alone nor a fit proves a material phase diagram.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
- Electronic structure calculations with dynamical mean-field theory (2006)Gabriel Kotliar, Sergey Y. Savrasov, Kristjan Haule and collaboratorsResearch paper
- A Common Thread: the pairing interaction for the unconventional superconductors (2012)Douglas J. Scalapino / University of California, Santa BarbaraResearch paper
Evidence and review
Inspected §§I–II: Hubbard model, self-energy/impurity mapping, local approximation and material-dependent double-counting limits; source check dated 2026-10-10. Scope is limited to the cited statements, equations and assumptions, not the whole publication. Inspected introduction, Hubbard model/exchange pp.21–23, pairing sections and conclusions: spin-fluctuation proposal and experimental phenomenology; source check dated 2026-10-10. Scope is limited to the cited statements, equations and assumptions, not the whole publication.
2026-10-10 · Author source inspection of the displayed claim, model assumptions and equations; independent exact-content and branch-inventory review is a separate gate. Contemporary status is a dated snapshot, not a promise of ongoing monitoring.
Entry details
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- research-physics-hubbard-correlations
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- Postgraduate & research reference