Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 4 of 4
Full-Text Articles in Physics
Flux States For The Infinite-U Limit Of The Hubbard Model, S. E. Barnes
Flux States For The Infinite-U Limit Of The Hubbard Model, S. E. Barnes
Physics Articles and Papers
For finite doping, δ, relative to half filling, it is shown, within the confines of a mean-field auxiliary-operator formulation, for the strictly infinite-U, i.e., J=0, limit of the two-dimensional Hubbard model, that the spinons generate a fictitious magnetic flux to which holons are subject and vice versa. For small doping, a flux state is the absolute ground state and has 1-δ=2p/q, where p/q is a rational fraction and the flux per plaquette is Φ=(p/q)Φ0, where Φ0 is the flux quantum. This phenomenon can be viewed upon as an all-electron Peierls instability or as broken statistical symmetry.
All-Electronic Peierls Instability In The Infinite-U Mean-Field Theory For The Hubbard Model, S. E. Barnes
All-Electronic Peierls Instability In The Infinite-U Mean-Field Theory For The Hubbard Model, S. E. Barnes
Physics Articles and Papers
It is shown, for a small hole doping relative to half filling, that the large-U limit of the Hubbard model (or J=0 limit of the t-J model) exhibits an all-electron Peierls instability towards a state with a charge-density wave. The resulting gap in the spinon spectrum renders the model an insulator.
Spin-Disordered Ground State For A Nearly Half-Filled Hubbard Model, S. E. Barnes
Spin-Disordered Ground State For A Nearly Half-Filled Hubbard Model, S. E. Barnes
Physics Articles and Papers
Following Nagaoka, the ground state of the large-U nearly half-filled Hubbard model is ‘‘ferromagnetic.’’ However, because of the anisotropic exchange energy JA, the physical Nagaoka ground state is nondegenerate and comprises a totally disordered spin state, i.e., a linear combination of all possible spin arrangements. For this ground state the susceptibility is Pauli-like but of a magnitude associated with a narrow band of width ∼JA while the holons, i.e., the charge excitations, correspond to spinless fermions with a band of width 2zt. Associated with the spinon sector are very poorly defined spin waves, i.e., bosons, with a …
Excitations In A Nearly Half-Filled Hubbard Model With U=∞, S. E. Barnes
Excitations In A Nearly Half-Filled Hubbard Model With U=∞, S. E. Barnes
Physics Articles and Papers
It is shown that, even near half filling, the elementary excitations of the large-U Hubbard model form wide bands of width ∼t, the intersite hopping integral, and that the slave-boson-based mean-field approximation is qualitatively wrong in the relevant limit. This large-U limit has no Kondo-type divergences.