Control of photons, electrons and spins in GaAs quantum wells using acoustic fields

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• Dr. Paulo Santos, Paul Drude Institute, Berlin
• Monday 05 December 2005, 14:15-15:15
• Mott Seminar Room, Cavendish Laboratory, Department of Physics.

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The dynamic modulation of the electronic and optical properties of GaAs low-dimensional structures by surface acoustic waves (SAWs) provides a convenient way of controlling photons, carriers, and spins. Efficient photon control takes place through the modulation of the dimensions and optical properties of GaAs-based photonic resonators by the acoustic field. The modulation creates a dynamic optical superlattice, which acts as an efficient optical switch. Carrier control employs the piezoelectric field induced by the SAW . The latter forms three-dimensionally confined and mobile potentials (dynamic quantum dots, DQDs) in an undoped quantum well (QW) structure, which transport photogenerated electron-hole pairs over hundreds of micrometers with the acoustic velocity. More important, photogenerated electron spins can be coherently transported in that way over distances approaching 100 micrometer, which corresponds to an increase in the electron spin lifetime of approximately two orders of magnitude. The long electron spin lifetimes are attributed to the reduction of the spin scattering mechanisms due to the DQD confinement. Finally, application of an external magnetic field enables the spin state to be modulated during transport, thus opening the way for application in spintronics.

This talk is part of the Semiconductor Physics series.

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