Inverse freezing in the cluster fermionic spin glass model with a transverse field

Abstract

The inverse freezing (IF) transition is studied with a cluster fermionicIsing spin glass model in the presence of a transverse magnetic fieldΓ. The model considers a disordered infinite-range interaction among magneticmoments of the clusters with a short-range ferromagnetic intracluster couplingJ0. The intercluster disorder is treated within a mean-field theory by using theframework of one-step replica symmetry breaking and the static approximation. Thistreatment results in an effective model that is computed by means of an exactdiagonalization method. In particular, in this fermionic problem, the chemical potentialμ andthe Γ introduce cluster charge fluctuations and quantum spin flipping,respectively. The results indicate an IF transition for a certain range ofμ. When the short-range interaction increases, the IF is still found. However, the intensity ofJ0 can affectthe charge fluctuation, introducing a second-order IF transition. On the other hand, the enhancementof Γ destroys the inverse freezing.