Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 3: Spintronik I

HL 3.7: Talk

Friday, March 4, 2005, 12:15–12:30, TU P164

Spin Transport and Manipulation by Dynamic Quantum Dots — •James A. H. Stotz, Rudolph Hey, Paulo V. Santos, and Klaus H. Ploog — Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany

We present a spatially resolved photoluminescence (PL) study of spin transport in confined geometries via a new form of quantum dots – denoted as dynamic quantum dots (DQDs). The DQDs are produced by the superposition of piezoelectric fields from surface acoustic waves (SAWs) propagating along orthogonal directions on a GaAs/(Al,Ga)As quantum well sample. Within the DQD array, spin polarized carriers are excited by circularly polarized laser light and captured by the DQDs. The carriers are then transported at a velocity determined by the SAWs, and the spin transport is detected by the circular polarization of the resulting PL. The photogenerated electrons and holes are spatially separated by the piezoelectric potential of the DQDs resulting in a dramatic increase of the spin-polarized PL signal and, conseqently, of the electron-spin lifetime. In addition, we demonstrate that the electron spins can be transported over distances exceeding 70 µm, which corresponds to a further increase in their spin lifetimes of more than an order of magnitude. These long spin lifetimes are attributed to the reduction of the D’yakonov-Perel’ spin scattering mechanism within the confinement potential of the DQDs. Futhermore, application of an external magnetic field enables the electron spin state to be manipulated during transport.