New universality class for the three-dimensional XY model with correlated impurities: Application to 4 He in aerogels
Carlos Vásquez-Romero, R. Paredes-Villegas, A. Hasmy, R. Jullien
Abstract
Encouraged by experiments on
4
He in aerogels, we confine planar spins in the pores of simulated aerogels (diffusion limited cluster-cluster aggregation) in order to study the effect of quenched disorder on the critical behavior of the three-dimensional XY model. Monte Carlo simulations and finite-size scaling are used to determine critical couplings
K
c
and exponents. In agreement with experiments, clear evidence of change in the thermal critical exponents
ν
and
α
is found at nonzero volume fractions of impurities. These changes are explained in terms of {\it hidden} long-range correlations within disorder distributions.