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Quantum Transport

AG von Oppen

Deterministic ratchets in asymmetric nanostructures

Location: Fachbereich Physik, SR E3Time: Thursday 12.07.2007, 14h c.t. |

A board of rigid disks on a triangular lattice
has been invented by Galton in 1889
to demonstrate the appearance of statistical laws
from dynamical motion. This system, also called
periodic Lorentz gas, has been proved to be completely
chaotic by Sinai in 60th. The dynamics remains chaotic also for
semidisks scatterers oriented in one direction.
In this case the inversion symmetry is broken but
the directed transport remains forbidden by the detailed balance principle.
This remains true also in presence of polarized monochromatic force
produced by microwave radiation. However, when dissipation is present,
a new stationary state is born from chaos as shown in [1].
It is characterized by a directed transport which can be
efficiently controlled by the microwave polarization even
if mean force is zero. Being universal this effect exists for
Maxwell or Fermi-Dirac thermostatted gas moving between semi-disks
in presence of a microwave field [2-5]. Nowadays technology allows
to realize the semidisk Galton board with a two-dimensional electron gas
in a superlattice of micron size antidots. In this case
the theory predicts appearance of strong currents induced
by microwave fields. This opens new possibilities
for creation of room temperature detectors of terahertz radiation.
Combined effects of magnetic and microwave fields will be also discussed.
(*) http://www.quantware.ups-tlse.fr/dima/

[1] A.D.Chepelianskii and D.L.Shepelyansky, Phys. Rev. B, 71, 052508 (2005).

[2] G.Cristadoro and D.L.Shepelyansky, Phys. Rev. E 71, 036111 (2005).

[3] A.D.Chepelianskii, Eur. Phys. J. B, 52, 389 (2006).

[4] M.V.Entin and L.I.Magarill, Phys. Rev. B 72, 205206 (2006).

[5] A.D.Chepelianskii, M.V.Entin, L.I.Magarill and D.L.Shepelyansky,
Eur. Phys. J. B v.56, p.323-333 (2007).

**More information:** F. von Oppen (vonoppenphysik.fu-berlin.de)

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