Intermittence and roughening of periodic elastic media - art. no. 036126

We analyze intermittence and roughening of an elastic interface or domain w all pinned in a periodic potential, in the presence of random-bond disorder in 1+1 and 2+1 dimensions. Though the ensemble average behavior is smooth, the typical behavior of a large sample is intermittent, and does not self- average to a smooth behavior. Instead, large fluctuations occur in the mean location of the interface and the onset of interface roughening is via an extensive fluctuation which leads to a jump in the roughness of order lambd a, the period of the potential. Analytical arguments based on extreme stati stics are given for the number of the minima of the periodicity visited by the interface and for the roughening crossover, which is confirmed by exten sive exact ground stare calculations.