AIP conference proceedings
First Order Phase Transition in a 3D disordered system
L. A. Fernández, A. Gordillo-Guerrero, Víctor Martín-Mayor, Juan Jesus Ruiz-Lorenzo, Jesús Clemente-Gallardo, Pierpaolo Bruscolini, Francisco M. Castejón, Pablo Echenique, José Félix Sáenz-Lorenzo
Abstract
We present a detailed numerical study on the effects of adding quenched impurities to a three dimensional system which in the pure case undergoes a strong first order phase transition (specifically, the ferromagnetic/paramagnetic transition of the site‐diluted four states Potts model). We can state that the transition remains first‐order in the presence of quenched disorder (a small amount of it) but it turns out to be second order as more impurities are added. A tricritical point, which is studied by means of Finite‐Size Scaling, separates the first‐order and second‐order parts of the critical line. The results were made possible by a new definition of the disorder average that avoids the diverging‐variance probability distributions that arise using the standard methodology. We also made use of a recently proposed microcanonical Monte Carlo method in which entropy, instead of free energy, is the basic quantity.