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Applied Physics A

, Volume 75, Issue 2, pp 237–246 | Cite as

Quantum ratchets and quantum heat pumps

  • H. Linke
  • T.E. Humphrey
  • P.E. Lindelof
  • A. Löfgren
  • R. Newbury
  • P. Omling
  • A.O. Sushkov
  • R.P. Taylor
  • H. Xu
Article

Abstract.

Quantum ratchets are Brownian motors in which the quantum dynamics of particles induces qualitatively new behavior. We review a series of experiments in which asymmetric semiconductor devices of sub-micron dimensions are used to study quantum ratchets for electrons. In rocked quantum-dot ratchets electron-wave interference is used to create a non-linear voltage response, leading to a ratchet effect. The direction of the net ratchet current in this type of device can be sensitively controlled by changing one of the following experimental variables: a small external magnetic field, the amplitude of the rocking force, or the Fermi energy. We also describe a tunneling ratchet in which the current direction depends on temperature. In our discussion of the tunneling ratchet we distinguish between three contributions to the non-linear current–voltage characteristics that lead to the ratchet effect: thermal excitation over energy barriers, tunneling through barriers, and wave reflection from barriers. Finally, we discuss the operation of adiabatically rocked tunneling ratchets as heat pumps.

PACS: 73.40.Ei; 73.23.Ad; 73.50.Fq; 7.20.Pe 

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Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  • H. Linke
    • 1
  • T.E. Humphrey
    • 2
  • P.E. Lindelof
    • 3
  • A. Löfgren
    • 4
  • R. Newbury
    • 2
  • P. Omling
    • 4
  • A.O. Sushkov
    • 2
  • R.P. Taylor
    • 1
  • H. Xu
    • 4
  1. 1.Department of Physics, University of Oregon, Eugene, OR 97403-1274, USAUS
  2. 2.School of Physics, University of New South Wales, Sydney 2052, AustraliaAU
  3. 3.Niels-Bohr-Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, DenmarkDK
  4. 4.Solid State Physics, Lund University, Box 118, 22100 Lund, SwedenSE

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