The electronic states of the Hubbard model are investigated by use of the composite operator method. In addition to the Hubbard operators, two other operators related with two-site composite excitations are included in the basis. Within the present formulation, higher-order composite excitations are reduced to the chosen operatorial basis by means of a procedure preserving the particle-hole symmetry. The positive comparison with numerical simulations for the double occupancy indicates that such approximation improves over the two-pole approximation. © 2003 Elsevier B.V. All rights reserved.
Effects of two-site composite excitations in the Hubbard model
AVELLA, Adolfo;MANCINI, Ferdinando;ODASHIMA, SATORU
2004-01-01
Abstract
The electronic states of the Hubbard model are investigated by use of the composite operator method. In addition to the Hubbard operators, two other operators related with two-site composite excitations are included in the basis. Within the present formulation, higher-order composite excitations are reduced to the chosen operatorial basis by means of a procedure preserving the particle-hole symmetry. The positive comparison with numerical simulations for the double occupancy indicates that such approximation improves over the two-pole approximation. © 2003 Elsevier B.V. All rights reserved.File in questo prodotto:
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