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TT: Fachverband Tiefe Temperaturen

TT 37: Transport: Nanoelectronics II - Spintronics and Magnetotransport

TT 37.8: Hauptvortrag

Donnerstag, 26. März 2009, 11:30–12:00, HSZ 105

Quantum dissipative spin ratchets — •Milena Grifoni — University of Regensburg, Regensburg, Germany

Rather than fighting it, so-called quantum Brownian motors take advantage of thermal noise and quantum tunneling to move efficiently microscopic entities, as e.g. electrons, along predetermined directions. Here we focus on a particular class of quantum Brownian motors, i.e., quantum ratchets which, due to broken spatial symmetry, produce movement in one direction from a force that may be acting at random. We shall discuss, in particular, how the ratchet effect can be used to produce pure spin currents, i.e., a finite spin current and the absence of charge transport. To this extent we consider electrons moving in a quasi-one-dimensional asymmetric periodic structure with Rashba spin-orbit interaction, strong dissipation and subject to ac-driving. We show that under a finite coupling strength between the orbital degrees of freedom the electron dynamics at low temperatures exhibits a pure spin ratchet behaviour with in-plane polarization. Moreover, the equilibrium spin currents are not destroyed by the presence of strong dissipation.