Thermodynamic and Magnetic Properties of Hubbard Lattices.

Karol Makuch, Jan Skolimowski, P B Chakraborty +2 more

Motivated by the rapidly growing possibilities for experiments with ultracold atoms in optical lattices, we investigate the thermodynamic properties of correlated lattice fermions in the presence of an external spin-dependent random potential. The corresponding model, a Hubbard model with spin-dependent local random potentials, is solved within dynamical mean-field theory. This allows us to present a comprehensive picture of the thermodynamic properties of this system. In particular, we show that for a fixed total number of fermions spin-dependent disorder induces a magnetic polarization. The magnetic response of the polarized system differs from that of a system with conventional disorder.

Eleftherios N. Economou

Andressa R. Medeiros-Silva, Natanael C. Costa, Thereza Paiva

Over the past few decades, magnetic frustration has been under intense debate due to its unusual properties. For instance, frustration in the kagome lattice suppresses long-range spin correlations, and it is expected to be a candidate for a spin liquid system. Therefore, with the advent of experiments with ultracold atoms, the interest in frustrated geometries has increased. Given this, in the present work we investigate the repulsive Hubbard model on the kagome lattice using unbiased quantum Monte Carlo simulations. We examine its thermodynamic properties, as well as the magnetic and transport response of the system at finite temperatures and different values of the repulsive interaction. From these results, we discuss the possible occurrence of adiabatic cooling, a quite important feature in ultracold systems, and the presence of a metal-to-insulator transition at a finite interaction strength. Our findings may guide future experiments in ultracold fermionic atoms on the kagome lattice.

Minoru Takahashi

Barbara Capogrosso-Sansone, Nikolay V. Prokof'ev, Boris V. Svistunov

Santos Filho, Adelino dos

In this work we obtain the magnetic and thermodynamic properties of the classical Hubbard model. This one is easier to handle than the original Hubbard model, and it maintains fundamental aspects like charge and particle-hole symmetry. We find the relationship between this and the Ising model. For square and simple cubic lattices, the thermodynamic properties and phase diagrams were calculated by Monte Carlo method. We show the behavior of internal energy, specific heat, and magnetic susceptibility as a function of the temperature. For the considered lattices, the ground state is anti-ferromagnetic. The Néel temperatures were found as a function of the electronic interaction in the case of half-filled band. In the limit of vanishing of diverging interaction, our results agree with the Ising model.