The half-filled Hubbard chain in the Composite Operator Method: A comparison with Bethe Ansatz
Dipartimento di Scienze Fisiche “E. R. Caianiello”, Università degli Studi di Salerno, Unità INFM di Salerno - 84081 Baronissi, Salerno, Italy
Accepted: 11 September 1998
The one-dimensional Hubbard model at half-filling is studied in the framework of the Composite Operator Method using a static approximation. A solution characterized by strong antiferromagnetic correlations and a gap for any non-zero on-site interaction U is found. The corresponding ground-state energy, double occupancy and specific heat are in excellent agreement with those obtained within the Bethe Ansatz. These results show that the Composite Operator Method is an appropriate framework for the half-filled Hubbard chain and can be applied to evaluate properties, like the correlation functions, which cannot be obtained by means of the Bethe Ansatz, except for some limiting cases.
PACS: 71.10.-w – Theories and models of many electron systems / 71.10.Fd – Lattice fermion models (Hubbard model, etc.) / 71.15.Th – Other methods
© EDP Sciences, 1998