title: First-order transition in a three-dimensional disordered system.
abstract: We present the first detailed numerical study in three dimensions of a first-order phase transition that remains first order in the presence of quenched disorder (specifically, the ferromagnetic-paramagnetic transition of the site-diluted four states Potts model). A tricritical point, which lies surprisingly near the pure-system limit and is studied by means of finite-size scaling, separates the first-order and second-order parts of the critical line. This investigation has been made possible by a new definition of the disorder average that avoids the diverging-variance probability distributions that plague the standard approach. Entropy, rather than free energy, is the basic object in this approach that exploits a recently introduced microcanonical Monte Carlo method.
authors: Departamento de Física Teórica I, Universidad Complutense, 28040 Madrid, Spain.
authors: L A
authors: LA
authors: Fernández
authors: A
authors: A
authors: Gordillo-Guerrero
authors: V
authors: V
authors: Martín-Mayor
authors: J J
authors: JJ
authors: Ruiz-Lorenzo