Critical Behavior of Superfluid 4He in Aerogel

We report Monte Carlo studies of the critical behavior of superfluid ⁴He in the presence of quenched disorder with long-range fractal correlations. Modeling aerogel as an incipient percolating cluster in 3D and weakening the bonds at the fractal sites, XY-model simulations demonstrate an increase in the superfluid density exponent ζ from 0.67+/-0.005 for the pure case to an apparent value of 0.722+/-0.005 in the presence of the fractal disorder, provided that the helium correlation length does not exceed the fractal correlation length.