Quantum ratchets and quantum heat pumps

H Linke, TE Humphrey, PE Lindelof, Anneli Löfgren, R Newbury, Pär Omling, AO Sushkov, RP Taylor, Hongqi Xu

Research output: Contribution to journalArticlepeer-review

67 Citations (SciVal)


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.
Original languageEnglish
Pages (from-to)237-246
JournalApplied Physics A: Materials Science & Processing
Issue number2
Publication statusPublished - 2002

Subject classification (UKÄ)

  • Condensed Matter Physics


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