Thermodynamics of infinite U Hubbard model

A K Mishra, Rishabh Kishore

Hubbard model plays a critical role in the study of strongly correlated electron systems. The only available exact solutions of 1-D Hubbard Hamiltonian, obtained through nested Bethe ansatz, show a spin charge decoupling for infinite U when there is no possibility of double occupancy of an electron orbital state. It had been shown that these features can be directly obtained by employing orthofermion algebra. In the present communication, the thermodynamic properties, namely, specific heat and entropy are provided for a 1-D chain and 2-D square lattice using orthofermion approach. It is shown that in 1-D, our results are identical to the known exact results. We have also compared the thermodynamic properties of free fermions and orthofermions in both 1-D and 2-D. Our thermodynamic results, based on orthofermion approach, can be used to ascertain the accuracy of the approximate methods employed in the context of infinite U Hubbard model.

Minoru Takahashi

D. Grensing, Heinz Koppe

Thomas Pruschke, Daniel Lee Cox, Mark Jarrell

We present results on the thermodynamic quantities, resistivity, and optical conductivity for the Hubbard model on a simple hypercubic lattice in infinite dimensions. Our results for the paramagnetic phase display the features expected from an intuitive analysis of the one-particle spectra and substantiate the similarity of the physics of the Hubbard model to those of heavy-fermion systems. The calculations were performed using an approximate solution to the single-impurity Anderson model, which is the key quantity entering the solution of the Hubbard model in this limit. To establish the quality of this approximation we compare its results, together with those obtained from two other widely used methods, to essentially exact quantum Monte Carlo results.

J. P. F. LeBlanc, Emanuel Gull

R. M. Noack, Florian Gebhard

We calculate the zero-temperature gap and quasiparticle weight of the half-filled Hubbard model with a random dispersion relation. After extrapolation to the thermodynamic limit, we obtain reliable bounds on these quantities for the Hubbard model in infinite dimensions. Our data indicate that the Mott-Hubbard transition is continuous; i.e., the quasiparticle weight becomes zero at the same critical interaction strength at which the gap opens.