Quantum ratchets and quantum heat pumps

Summary, in English

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.

• Author: H Linke; TE Humphrey; PE Lindelof; Anneli Löfgren; R Newbury; Pär Omling; AO Sushkov; RP Taylor; Hongqi Xu
• Department/s: Solid State Physics
• Publishing year: 2002
• Language: English
• Pages: 237-246
• Publication/Series: Applied Physics A: Materials Science & Processing
• Volume: 75
• Issue: 2
• Links: http://dx.doi.org/10.1007/s003390201335
• Document type: Journal article
• Publisher: Springer
• Topic: Condensed Matter Physics
• Status: Published
• ISBN/ISSN/Other: ISSN: 1432-0630