Physical review. B, Condensed matter
Interface energy in random systems
Bernard Derrida, J. Vannimenus
Abstract
We study the interface energy $\ensuremath{\sigma}$ as a function of disorder in two-dimensional Ising-type systems at $T=0$ for the percolation and frustration models. Our approach consists in calculating this energy for long strips of varying widths by a random sampling method, then extrapolating the results. In the weak-disorder limit, very wide strips may be studied and accurate values are obtained for the first-order correction to the interface energy in both models. Only moderate widths (up to $N=9\ensuremath{-}10$) can be studied in the general situation and we use finite-size scaling to analyze the data in the region of the threshold, where $\ensuremath{\sigma}$ vanishes with a critical exponent $v$. For percolation, we obtain $\frac{v}{\ensuremath{\nu}}=0.98\ifmmode\pm\else\textpm\fi{}0.05$, where $\ensuremath{\nu}$ is the correlation-length exponent, in agreement with Deutscher and Rappaport's proposal that $v=\ensuremath{\nu}$ exactly. The analysis of the results is more difficult in the case of frustration, because size effects are important and the scaling region is not reached for $N=9$. Our data show that Monte Carlo results for $\ensuremath{\sigma}$ are unreliable and that much care is necessary to reach firm conclusions on the frustration threshold ${x}_{c}$ or the exponents $\ensuremath{\nu}$ and $v$.