Phase diagrams of the Bose-Hubbard model at finite temperature

Abstract

The phase transitions in the Bose-Hubbard model are investigated. A single-particle Green's function is calcu- lated in the random phase approximation and the formalism of the Hubbard operators is used. The regions of existence of the superfluid and Mott insulator phases are established and the (μ, t) (the chemical potential - transfer parameter) phase diagrams are built. The effect of temperature change on this transition is analyzed and the phase diagram in the (T, μ) plane is constructed. The role of thermal activation of the ion hopping is investigated by taking into account the temperature dependence of the transfer parameter. The reconstruction of the Mott-insulator lobes due to this effect is analyzed. © I.V. Stasyuk, T.S. Mysakovych.