The high temperature series for the Hubbard model

B. Sriram Shastry, Edward Perepelitsky, Andrew Galatas +3 more

W. Brauneck

D. F. B. ten Haaf, J. M. J. van Leeuwen

A method is described to obtain high-temperature series expansions for the grand potential and the nearest-neighbor correlation of the z-component of the spin in the Hubbard model. The method is applied to the square and simple cubic lattices. The series have been calculated up to eighth order in \ensuremath{\beta}t. The convergence of the series is discussed and a comparison with previous results in the literature is made. The present calculations contain an indication for the occurrence of a Nagaoka-like phase.

Marcel Franz, M. Noga

Katsunori Kubo, Masahito Tada

The high temperature series of the thermodynamic potential and the uniform susceptibility have been investigated for the single-band Hubbard model in the strong correlation limit. It is rigorously shown that the series absolutely converge both in the low density and the half-filled limit. Correct first terms have been obtained up to the ninth order in terms of the inverse temperature. Coefficients of the series are oscillating rapidly as functions of the occupation probability of electrons.

Jon Henderson, J. Oitmaa, M. C. B. Ashley

We study the single-band Hubbard model via high-temperature expansions to order (\ensuremath{\beta}t${)}^{9}$ for the standard two- and three-dimensional lattices. Series are derived for the grand potential and for the ferromagnetic susceptibility, for general values of the Coulomb repulsion parameter U and electron density n. The series are difficult to analyze with any degree of precision, but estimates are obtained for the ferromagnetic critical temperature.