Participating group members: |
Peter Reimann |

Main external cooperation partners: |
Peter Hänggi, Michael Thorwart |

Interplay of quantum mechanical barrier tunneling and thermally activated barrier crossing in a periodically rocked ratchet potential. At high temperatures, thermal noise dominates, resulting in an average preferential direction of motion to the right. At low temperatures, tunneling to the left dominates. |

We are interested in the characteristic signatures of quantum mechanical effects on top of thermal noise and dissipation in ratchet systems and stochastic resonance. Further issues are the anomalous (non-monotonous) temperature-dependence of escape rates out of metastable states and step-like quantum-signatures in hysteresis-loops and resonance-like features of tunneling-rates as observed in Mn-acetate-crystals. The basis of our approach is the Feynman-Vernon- and Caldeira-Leggett-formalism in order to treat quantum-tunneling in the presence of dissipation and thermal fluctuations.

Main publications:

P. Reimann, M. Grifoni, and P. Hänggi

*Quantum Ratchets*

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

M. Thorwart, P. Reimann, P. Jung, and R.F. Fox

*Quantum Steps in Hysteresis Loops*

Phys. Lett. A **239**, 233 (1998)

M. Thorwart, P. Reimann, P. Jung, and R.F. Fox

*Quantum Hysteresis and Resonant Tunneling in Bistable Systems*

Chem. Phys. **235**, 61 (1998)

P. Hänggi and P. Reimann

*Quantum Ratchet Reroute Electrons*

Physics World **12**, 21 (1999)

M. Thorwart, P. Reimann, and P. Hänggi

*Iterative Algorithm versus Analytic Solutions of the
Parametrically Driven Dissipative Quantum Harmonic Oscillator*

Phys. Rev. E **62**, 5808 (2000)

*Last update on August 2, 2004.*