Participating group members: |
Peter Reimann, Mykhaylo Evstigneev |

Main cooperation partners: |
Chris Van den Broeck, Andreas Engel, Peter Hänggi, Roger Filliger |

Ratchet and pawl: The gas molecules hitting the propeller cause the gear to turn, but which way does it go? If spring and pawl work ``correctly'', the gear can only turn counterclockwise. But when thermal noise causes the spring to release and reengage, the gear tends to turn clockwise because of the asymmetry of the gear teeth. This effect dominates whenever more heat is applied to the spring than to the gas. |

We address the question, how the interplay of a nonlinear dynamics and unbiased random fluctuations may generate directed macroscopic transport in spatially periodic structures. This so-called ratchet effect arises, for instance, when the symmetry of a periodic potential is broken (ratchet potential). Besides its theoretical interest as a nonlinear stochastic process far from thermal equilibrium (see figure) this mechanism plays an important role in the context of biological transport (e.g. in motor enzymes, and ion pumps) and nano-technological applications like particle separation and particle pumps (see links to own projects below).

A comprehensive review:

P. Reimann

*Brownian Motors: Noisy Transport far from Equilibrium*

Phys. Rep. **361**, 57 (2002)

Papers covering both theory and experiments:

A. Engel, H. W. Müller, P. Reimann, and A. Jung

*Ferrofluids as thermal ratchets*

Phys. Rev. Lett **91**, 060602 (2003)

This work is summarized in a
poster
and illustrated by a
movie (1.4 MB).

D. van der Meer, P. Reimann, K. van der Weele, and D. Lohse

*Spontaneous Ratchet Effect in a Granular Gas*

Phys. Rev. Lett. **92**, 184301 (2004)

This work is illustrated by a
movie (32 MB).

P. Tierno, P. Reimann, T.H. Johansen, and F. Sagues

* Giant Transversal Particle Diffusion in a Longitudinal Magnetic Ratchet*

Phys. Rev. Lett. **105**, 230602 (2010),
Physical Review Focus

L. Bogunovic, R. Eichhorn, J. Regtmeier, D. Anselmetti, and P. Reimann

* Particle sorting by a structured microfluidic ratchet device with tunable selectivity: theory and experiment*

Soft Matter **8**, 3900 (2012)

A selection of basic theoretical studies:

R. Bartussek, P. Reimann, and P. Hänggi

*Precise Numerics versus Theory for Correlation Ratchets*

Phys. Rev. Lett. **76**, 1166 (1996)

P. Reimann, R. Bartussek, R. Häussler, and P. Hänggi

*Brownian Motors Driven by Temperature Oscillations*

Phys. Lett. A **215**, 26 (1996)

P. Reimann

*Supersymmetric Ratchets*

Phys. Rev. Lett. **86**, 4992 (2001)

P. Reimann and M. Evstigneev

*Pulsating potential ratchet*

Europhys. Lett. **78**, 50004 (2007)

R. Filliger and P. Reimann

* Brownian Gyrator: A Minimal Heat Engine on the Nanoscale*

Phys. Rev. Lett. **99**, 230602 (2007)

S. von Gehlen, M. Evstigneev, and P. Reimann

* Dynamics of a dimer in a symmetric potential: Ratchet effect generated by an internal degree of freedom*

Phys. Rev. E **77**, 031136 (2008)

S. von Gehlen, M. Evstigneev, and P. Reimann

*Ratchet effect of a dimer with broken friction symmetry in a symmetric potential *

Phys. Rev. E **79**, 031114 (2009)

Theoretical predictions which have later been verified by
experimental groups

(see
Science 286, 2314 (1999),
Science 300, 1235 (2003),
and Nature 424, 53 (2003),
respectively)

P. Reimann, M. Grifoni, and P. Hänggi

*Quantum Ratchets*

Phys. Rev. Lett. **79**, 10 (1997)

P. Reimann

*Current Reversal in a White Noise driven flashing Ratchet*

Phys. Rep. **290**, 149 (1997)

C. Kettner, P. Reimann, P. Hänggi, and F. Müller

*Drift Ratchet*

Phys. Rev. E **61**, 312 (2000)

Related links:

Our own project on new migration mechanisms in microfluidic systems

Our own project on granular gases

Our own project on noise-induced collective phenomena far from equilibrium

Our own project on decay of complex metastable states

Our own project on open quantum systems

Molecular motor animation

*Last modified on 2012-03-14*