Interface fluctuations in disordered systems: Universality and non-Gaussian statistics

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We employ a functional renormalization group to study interfaces in the presence of a pinning potential in d=4-ε dimensions. In contrast to a previous approach [D.S. Fisher, Phys. Rev. Lett. 56, 1964 (1986)] we use a soft-cutoff scheme. With the method developed here we confirm the value of the roughness exponent ζ≈ 0.2083 ε in order ε. Going beyond previous work, we demonstrate that this exponent is universal. In addition, we analyze the generation of higher cumulants in the disorder distribution and the role of temperature as a dangerously irrelevant variable.