Cole David, Bending Simon, Savel'ev Sergey, Grigorenko Alexander, Tamegai Tsuyoshi, Nori Franco
Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY, UK.
Nat Mater. 2006 Apr;5(4):305-11. doi: 10.1038/nmat1608. Epub 2006 Mar 12.
Initially inspired by biological motors, new types of nanodevice have been proposed for controlling the motion of nanoparticles. Structures incorporating spatially asymmetric potential profiles (ratchet substrates) have been realized experimentally to manipulate vortices in superconductors, particles in asymmetric silicon pores, as well as charged particles through artificial pores and arrays of optical tweezers. Using theoretical ideas, we demonstrate experimentally how to guide flux quanta in layered superconductors using a drive that is asymmetric in time instead of being asymmetric in space. By varying the time-asymmetry of the drive, we are able experimentally to increase or decrease the density of magnetic flux at the centre of superconducting samples that have no spatial ratchet substrate. This is the first ratchet without a ratchet potential. The experimental results can be well described by numerical simulations considering the dragging effect of two types of vortices penetrating layered superconductors in tilted magnetic fields.
最初受生物马达的启发，人们提出了新型纳米器件来控制纳米粒子的运动。包含空间不对称势分布（棘轮衬底）的结构已通过实验实现，用于操纵超导体中的涡旋、非对称硅孔中的粒子，以及通过人工孔和光镊阵列操纵带电粒子。利用理论思想，我们通过实验证明了如何使用时间不对称而非空间不对称的驱动来引导层状超导体中的磁通量子。通过改变驱动的时间不对称性，我们能够通过实验增加或减少没有空间棘轮衬底的超导样品中心处的磁通量密度。这是首个没有棘轮势的棘轮。考虑到两种类型的涡旋在倾斜磁场中穿透层状超导体的拖曳效应，数值模拟能够很好地描述实验结果。
