DOI: https://doi.org/10.30970/jps.03.474
THERMODYNAMICS OF THE 2D HUBBARD MODEL
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Journal of Physical Studies 3(4), 474–491 (1999)
DOI: https://doi.org/10.30970/jps.03.474 THERMODYNAMICS OF THE 2D HUBBARD MODEL |
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F. Mancini1,
H. Matsumoto2,
D. Villani3
1Dipartimento di Scienze Fisiche "E. R. Caianiello",
Unità INFM di Salerno - Università di Salerno
84081 Baronissi, Salerno, Italy
2Department of Applied Physics,
Seikei University
Tokyo 180, Japan
3Serin Physics Laboratory, Rutgers University
Piscataway, New Jersey 08855-0849, USA
A theoretical analysis of the thermodynamic response functions of the 2D single–band Hubbard model is carried out by means of the composite operator method. It is shown that all the features of these quantities can be explained by looking at the dependence of the thermodynamic variables on their conjugate ones. In this way, the electronic specific heat and the entropy per site are determined in the paramagnetic phase. Also, for the electronic specific heat and internal energy we present two different schemes of calculation. It is found that the numerical data from quantum Monte Carlo techniques for the internal energy and electronic specific heat are well reproduced by determining them through the first and second temperature derivatives of the chemical potential. The anomalous normal state properties in hole–doped cuprate high $T_c$ superconductors are also well described. Finally, we obtain several characteristic crossing points for the response functions when plotted versus some thermodynamic variables. These peculiar features indicate the existence of more than one energy scale competing with thermal excitations and indicate, as already noted by Vollhardt, a crossover from a non–interacting to a highly correlated behaviour.