Department of Physics, Emory University, Atlanta, GA 30033, USA.
Soft Matter. 2017 Feb 8;13(6):1142-1155. doi: 10.1039/c6sm02072k.
The Casimir effect arises when long-ranged fluctuations are geometrically confined between two surfaces, leading to a macroscopic force. Traditionally, these forces have been observed in quantum systems and near critical points in classical systems. Here we show the existence of Casimir-like forces between two pinned particles immersed in two-dimensional systems near the jamming transition. We observe two components to the total force: a short-ranged, depletion force and a long-ranged, repulsive Casimir-like force. The Casimir-like force dominates as the jamming transition is approached, and when the pinned particles are much larger than the ambient jammed particles. We show that this repulsive force arises due to a clustering of particles with strong contact forces around the perimeter of the pinned particles. As the separation between the pinned particles decreases, a region of high-pressure develops between them, leading to a net repulsive force.
当长程涨落被几何限制在两个表面之间时，就会产生卡西米尔效应，从而导致宏观力的出现。传统上，这些力在量子系统和经典系统的临界点附近被观察到。在这里，我们展示了在二维系统中两个被钉住的粒子在临近阻塞转变时存在类似于卡西米尔的力。我们观察到总力的两个分量：短程的耗尽力和长程的、排斥的类似于卡西米尔的力。当接近阻塞转变时，类似于卡西米尔的力占据主导地位，并且当被钉住的粒子比周围的阻塞粒子大得多时。我们表明，这种排斥力是由于在被钉住的粒子周围具有强接触力的粒子的聚集而产生的。随着被钉住的粒子之间的分离减小，在它们之间形成了一个高压区域，导致净排斥力。
