Open Quantum Systems

Participating group members: Peter Reimann
Main external cooperation partners: Peter Hänggi, Michael Thorwart

quantum ratchet 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.