Author:

Abstract:

Controlled motion of nanoparticles has attracted recently a lot of attention in biology and physics [1]. In biology, typical examples are ion channels in cell membranes [2], biological motors [3]; in physics particle [4], charge [5] and vortex [6] ratchets, optical tweezers[7]. In spite of a broad variety, here the underlying principles of these effects have many remarkable similarities which make it possible to use new findings, discovered for a given type of the devices, for controlling the motion of nanoparticles in other devices in general. The idea of applying the ratchet mechanism to the case of vortices in type-II superconductors was introduced by Lee et al. [8]. Their theoretical research was invoked by the development of recent lithographic techniques, allowing to modulate material parameters on the scale of the coherence length ξ and the penetration length λ. This modulation creates a periodic pinning landscape for the present vortices, which depends on the properties of the periodic structuring. Breaking the spatial symmetry of the pinning potential results in a so-called ratchet potential capable of rectifying the motion of vortices. The tunability of these kind of systems makes it an ideal candidate to study the ratchet effect in general. Several kinds of pinning potentials were investigated [9-11], either magnetic or nonmagnetic. A detailed investigation of the effects of temperature and magnetic field on the ratchet effect will increase our knowledge of this kind of systems and pave the road towards new devices capable of manipulating vortex motion. [1] Special issue on Ratchets and Brownian Motors: Basic, Experiments and Applications, edited by H. Linke, Appl. Phys. A: Mater. Sci. Process. 75, 167 (2002). [2] R. D. Astumian, J. Phys. Chem. 100, 19075 (1996). [3] J. Howard, Nature 89, 561 (1997). [4] S. Matthias and F. Müller, Nature 424, 53 (2003). [5] H. Linke et al., Science 286, 2314 (1999). [6] J. E. Villegas et al., Science 302, 1188 (2003). [7] D.G. Grier, Nature 424, 810-816 (2003). [8] C.-S. Lee, B. Jankó, I. Derényi, and A.-L. Barabási, Nature 400, 337 (1999). [9] J. Van de Vondel et al., Phys. Rev. Lett. 94, 057003 (2005). [10] C.C. de Souza Silva, J. Van de Vondel, M. Morelle and V.V. Moshchalkov, Nature 440, 651 (2006). [11] C. C. de Souza Silva et al., Phys. Rev. Lett.