Site Dilution in the Half-Filled One-Band Hubbard Model: Ring Exchange, Charge Fluctuations and Application to La2Cu_{1-x}(Mg/Zn)_xO4
| Autor: | Delannoy, J. -Y. P., Del Maestro, A. G., Gingras, M. J. P., Holdsworth, P. C. W. |
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| Rok vydání: | 2008 |
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| Zdroj: | Phys. Rev. B 79, 224414 (2009) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevB.79.224414 |
| Popis: | We study the ground state quantum spin fluctuations around the N\'eel ordered state for the one-band ($t,U$) Hubbard model on a site-diluted square lattice. An effective spin Hamiltonian, $H_{\rm s}^{(4)}$, is generated using the canonical transformation method, expanding to order $t(t/U)^3$. $H_{\rm s}^{(4)}$ contains four-spin ring exchange terms as well as second and third neighbor bilinear spin-spin interactions. Transverse spin fluctuations are calculated to order $1/S$ using a numerical real space algorithm first introduced by Walker and Walsteadt. Additional quantum charge fluctuations appear to this order in $t/U$, coming from electronic hopping and virtual excitations to doubly occupied sites. The ground state staggered magnetization on the percolating cluster decreases with site dilution $x$, vanishing very close to the percolation threshold. We compare our results in the Heisenberg limit, $t/U \to 0$, with quantum Monte Carlo (QMC) results on the same model and confirm the existence of a systematic $x$-dependent difference between $1/S$ and QMC results away from $x=0$. For finite $t/U$, we show that the effects of both the ring exchange and charge fluctuations die away rapidly with increasing $t/U$. We use our finite $t/U$ results to make a comparison with results from experiments on La$_2$Cu$_{1-x}$(Mg/Zn)$_x$O$_4$. Comment: 21 pages, 2 columns. 13 figures |
| Databáze: | arXiv |
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