IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Electronics Thursday Sessions
       Session EL-ThM

Invited Paper EL-ThM3
Ratchets, Heat Pumps and Maxwell's Demon: Quantum Transport in the Non-linear Regime

Thursday, November 1, 2001, 9:00 am, Room 124

Session: Quantum Electronics
Presenter: H. Linke, Univ. of Oregon, Eugene
Authors: H. Linke, Univ. of Oregon, Eugene
T.E. Humphrey, Univ. of New South Wales, Australia
P.E. Lindelof, Niels-Bohr Inst., Denmark
A. Lofgren, Lund Univ., Sweden
R. Newbury, Univ. of New South Wales, Australia
P. Omling, Lund Univ., Sweden
W.D. Sheng, Lund Univ., Sweden
A.O. Sushkov, Univ. of New South Wales, Australia
A. Svensson, Lund Univ., Sweden
R.P. Taylor, Univ. of Oregon, Eugene
H.Q. Xu, Lund Univ., Sweden
Correspondent: Click to Email
Ratchets are non-equilibrium systems in which directed particle motion is generated using spatial or temporal asymmetry, in the absence of time-averaged macroscopic forces or gradients. After introducing general examples for ratchets and their application s, an overview will be given on a series of recent experiments on so-called quantum ratchets for electrons. These devices are based on GaAs/AlGaAs heterostructures containing a two-dimensional electron gas. The non-linear response of a spatially asymmetri c nanostructure (such as a triangular quantum dot) to an applied voltage is used to partially rectify a symmetric AC voltage. The required non-linear behaviour is generated using quantum effects, such as electron interference or tunneling through an asymm etric energy barrier. A particularly interesting observation is that the direction of the current generated in tunneling ratchets depends on energy, that is, the net flow of electrons at low energy is in a direction opposite to that of electrons at highe r energy. This observation implies that quantum ratchets perform an energy-sorting task similar to that assigned to Maxwell's demon - that is, they may act as heat pumps or even as heat engines. We will discuss the properties of such quantum heat pumps, focusing the discussion on the thermodynamic limits to their efficiency.