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Condensed Matter > Strongly Correlated Electrons
Title: Nonstandard Hubbard model and electron pairing
(Submitted on 31 Jul 2023 (v1), last revised 30 Apr 2024 (this version, v3))
Abstract: We present a non-standard Hubbard model applicable to arbitrary single-particle potential profiles and inter-particle interactions. Our approach involves a novel treatment of Wannier functions, free from the ambiguities of conventional methods and applicable to finite systems without periodicity constraints. To ensure the consistent evaluation of Wannier functions, we develop a perturbative approach, utilizing the barrier penetration coefficient as a perturbation parameter. With the newly defined Wannier functions as a basis, we derive the Hubbard Hamiltonian, revealing the emergence of density-induced and pair tunneling terms alongside standard contributions. Our investigation demonstrates that long-range inter-particle interactions can induce a novel mechanism for repulsive particle pairing. This mechanism relies on the effective suppression of single-particle tunneling due to density-induced tunneling. Contrary to expectations based on the standard Hubbard model, an increase in inter-particle interaction does not lead to an insulating state. Instead, our proposed mechanism implies the coherent motion of correlated electron pairs, similar to bound states within a multi-well system, resistant to decay from single-electron tunneling transitions. These findings carry significant implications for various phenomena, including the formation of flat bands, the emergence of superconductivity in twisted bilayer graphene, and the possibility of a novel metal-insulator transition.
Submission history
From: Matteo Zendra [view email][v1] Mon, 31 Jul 2023 15:01:16 GMT (860kb,D)
[v2] Thu, 28 Mar 2024 11:01:12 GMT (2230kb,D)
[v3] Tue, 30 Apr 2024 09:37:56 GMT (2232kb,D)
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