# Fluctuation induced forces in critical films with disorder at their surfaces

## TL;DR

This paper studies how quenched surface disorder influences the critical Casimir forces between two surfaces in fluids near criticality, revealing an attractive disorder-induced contribution through analytical and simulation methods.

## Contribution

It provides an analytical field-theoretic analysis of disorder effects on critical Casimir forces, supported by Monte Carlo simulations, in the context of the Ising universality class.

## Key findings

- Disorder induces an attractive contribution to Casimir forces.
- Analytical results agree with Monte Carlo simulations.
- Surface disorder affects critical interactions in fluid films.

## Abstract

We investigate the effect of quenched surface disorder on effective interactions between two planar surfaces immersed in fluids which are near criticality and belong to the Ising bulk universality class. We consider the case that, in the absence of random surface fields, the surfaces of the film belong to the surface universality class of the so-called ordinary transition. We find analytically that in the linear weak-coupling regime, i.e., upon including the mean-field contribution and Gaussian fluctuations, the presence of random surface fields with zero mean leads to an attractive, disorder-induced contribution to the critical Casimir interactions between the two confining surfaces. Our analytical, field-theoretic results are compared with corresponding Monte Carlo simulation data.