Anneli Löfgren
Forskningsadministrativ chef, avdelningen för fasta tillståndets fysik
Quantum ratchets and quantum heat pumps
Författare
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.
Avdelning/ar
- Fasta tillståndets fysik
Publiceringsår
2002
Språk
Engelska
Sidor
237-246
Publikation/Tidskrift/Serie
Applied Physics A: Materials Science & Processing
Volym
75
Issue
2
Dokumenttyp
Artikel i tidskrift
Förlag
Springer
Ämne
- Condensed Matter Physics
Status
Published
ISBN/ISSN/Övrigt
- ISSN: 1432-0630