In purely repulsive, C4v-symmetric Hubbard clusters a correlation effect produces an effective two-body attraction and pairing; the key ingredient is the availability of W=0 pairs, that is, two-body solutions of appropriate symmetry. We study the tunneling of bound pairs in rings of 5-site units connected by weak intercell links; each unit has the topology of a CuO4 cluster and a repulsive interaction is included on every site. Further, we test the superconducting nature of the response of this model to a threading magnetic field. We present a detailed numerical study of the two-unit ring filled with 6 particles and the three-unit ring with 8 particles; in both cases a lower filling yields normal behavior. In previous studies on 1d Hubbard chains, level crossings were reported (half-integer or fractional Aharonov-Bohm effect) which however cannot be due to superconducting pairs. In contrast, the nontrivial basis of clusters carrying W=0 pairs leads to genuine Superconducting Flux Quantization (SFQ). The data are understood in terms of a cell-perturbation theory scheme which is very accurate for weak links. This low-energy approach leads to an effective hard core boson Hamiltonian which naturally describes itinerant pairs and SFQ in mesoscopic rings. For the numerical calculations, we take advantage of a recently proposed exact diagonalization technique which can be generally applied to many-fermion problems and drastically reduces the size of the matrices to be handled.

Callegari, A., Cini, M., Perfetto, E., Stefanucci, G. (2003). Symmetric Hubbard systems with superconducting magnetic response. THE EUROPEAN PHYSICAL JOURNAL. B, CONDENSED MATTER PHYSICS, 34(4), 455-466 [10.1140/epjb/e2003-00244-x].

Symmetric Hubbard systems with superconducting magnetic response

CINI, MICHELE;Perfetto, E;STEFANUCCI, GIANLUCA
2003-01-01

Abstract

In purely repulsive, C4v-symmetric Hubbard clusters a correlation effect produces an effective two-body attraction and pairing; the key ingredient is the availability of W=0 pairs, that is, two-body solutions of appropriate symmetry. We study the tunneling of bound pairs in rings of 5-site units connected by weak intercell links; each unit has the topology of a CuO4 cluster and a repulsive interaction is included on every site. Further, we test the superconducting nature of the response of this model to a threading magnetic field. We present a detailed numerical study of the two-unit ring filled with 6 particles and the three-unit ring with 8 particles; in both cases a lower filling yields normal behavior. In previous studies on 1d Hubbard chains, level crossings were reported (half-integer or fractional Aharonov-Bohm effect) which however cannot be due to superconducting pairs. In contrast, the nontrivial basis of clusters carrying W=0 pairs leads to genuine Superconducting Flux Quantization (SFQ). The data are understood in terms of a cell-perturbation theory scheme which is very accurate for weak links. This low-energy approach leads to an effective hard core boson Hamiltonian which naturally describes itinerant pairs and SFQ in mesoscopic rings. For the numerical calculations, we take advantage of a recently proposed exact diagonalization technique which can be generally applied to many-fermion problems and drastically reduces the size of the matrices to be handled.
2003
Pubblicato
Rilevanza internazionale
Articolo
Sì, ma tipo non specificato
Settore FIS/03 - FISICA DELLA MATERIA
English
Con Impact Factor ISI
Callegari, A., Cini, M., Perfetto, E., Stefanucci, G. (2003). Symmetric Hubbard systems with superconducting magnetic response. THE EUROPEAN PHYSICAL JOURNAL. B, CONDENSED MATTER PHYSICS, 34(4), 455-466 [10.1140/epjb/e2003-00244-x].
Callegari, A; Cini, M; Perfetto, E; Stefanucci, G
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/97086
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