Estructura i Constituents de la Matèria, Universitat de Barcelona, Avenida Diagonal 647, 08028 Barcelona, Spain and Institut de Nanociència i Nanotecnologia IN2UB, Universitat de Barcelona, 08028 Barcelona, Spain.
Institute of Physics, Universität Bayreuth, 95440 Bayreuth, Germany.
Phys Rev Lett. 2014 Jan 31;112(4):048302. doi: 10.1103/PhysRevLett.112.048302.
We study the collective transport of paramagnetic colloids driven above a magnetic bubble lattice by an external rotating magnetic field. We measure a direct ratchet current which rises in integer and fractional steps with the field amplitude. The stepwise increase is caused by excluded volume interactions between the particles, which form composite clusters above the bubbles with mobile and immobile occupation sites. Transient energy minima located at the interstitials between the bubbles cause the colloids to hop from one composite cluster to the next with synchronous and period doubled modes of transport. The colloidal current may be polarized to make selective use of type up or type down interstitials.
我们研究了在外加旋转磁场作用下顺磁胶体在磁泡格子上的集体输运。我们测量了一个随着磁场幅度呈整数和分数阶增加的直接棘轮电流。这种阶跃式的增加是由粒子之间的排斥体积相互作用引起的，这些粒子在气泡上方形成了具有可动和不可动占据位置的复合团簇。位于气泡之间的瞬态能量极小值导致胶体以同步和倍周期的输运模式从一个复合团簇跃迁到下一个复合团簇。胶体电流可以被极化，以便选择性地利用类型向上或类型向下的间隙。
