Löwen H
Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany.
J Phys Condens Matter. 2009 Nov 25;21(47):474203. doi: 10.1088/0953-8984/21/47/474203. Epub 2009 Nov 5.
The physics of colloidal suspensions confined in slits and cavities has significantly advanced during the last twenty years. In particular, freezing transitions in confinement have been addressed by theory and simulations and experimental realizations were proposed to confine colloidal particles to two dimensions. After reviewing this progress, we discuss the generalization to time-dependent confinement which leads to nonequilibrium situations. This is elaborated further for unstable situations where the particles can leave the confinement. In particular, the completely overdamped Brownian motion of a colloidal particle in a time-dependent harmonic trap is considered. The analytically soluble model of a time-dependent quadratic potential is used to extract the dynamical properties of the potential if the potential undergoes periodic switching from a confining harmonic potential to an unstable one. The amplitudes of the oscillating particle response can strongly grow in time, which we refer to as 'giant breathing'. This giant breathing process occurs also in anharmonic potentials and is verifiable in real-space experiments of colloids in laser-optical fields.
在过去二十年中，限制在狭缝和腔体中的胶体悬浮液物理学取得了显著进展。特别是，理论和模拟已经研究了受限条件下的冻结转变，并提出了将胶体颗粒限制在二维空间的实验方法。在回顾这一进展之后，我们讨论了向随时间变化的限制条件的推广，这会导致非平衡情况。对于粒子可以离开限制区域的不稳定情况，我们将进一步阐述这一点。特别地，我们考虑了胶体粒子在随时间变化的简谐势阱中的完全过阻尼布朗运动。如果势从限制简谐势周期性切换到不稳定势，我们使用随时间变化的二次势的解析可解模型来提取势的动力学性质。振荡粒子响应的振幅会随时间强烈增长，我们将其称为“巨呼吸”。这种巨呼吸过程也会出现在非简谐势中，并且可以在激光光学场中胶体的实空间实验中得到验证。
