Thermal Ratchets in Physics

Thermal ratchets are overdamped systems that transport Brownian particles with nonzero macroscopic velocity along one-dimensional asymmetric periodic structures due to the effect of nonequilibrium fluctuations, although on average no macroscopic force is acting. It is believed that various biological motion can be explained by the function of tiny motor proteins operating at the molecular scale using the ratchet effect. The statistical description of these mechanism is often referred to thermal ratchets or Brownian ratchets. Our research group at Notre Dame, led by Professor A.-L. Barabási, focuses on the application of the ratchet effect to various systems in condensed matter physics.
Vortex Dynamics

Reducing vortex density in superconductors
[ Nature 400, 337--340 (1999).]

Scanning SQUID microscope image of a thin-film high-Tc washer SQUID,
showing vortices trapped in the bulk of the washer.(Courtesy J.R. Kirtley.)
(J.R. Kirtley et. al., Appl. Phys. Lett. 66, 1138--1140)
We propose the use of the ratchet effect to remove the vortices from the SC.

Smoothing surface in MBE

Ratchet effect in surface electromigration
[ Physical Review Letters 80, 1473--1476 (1998). ]

STM images of mound formation during the deposition of Cu on Cu(100).
(J.-K. Zuo et. al., Phys. Rev. Lett. 78, 2791--2794)
We propose the use of the ratchet effect to smooth surface,
eliminating mound formation.

since June 14, 1999