Berlin 2005 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 20: Symposium: Single Photon Sources and Spectroscopy of Individual Quantum Systems

HL 20.3: Vortrag

Samstag, 5. März 2005, 11:45–12:15, TU P270

Optically initialization of single spins in semiconductor quantum dots — •Jonathan Finley , Miro Kroutvar, Dominik Heiss, Max Bichler, and Gerhard Abstreiter — Walter Schottky Institut and Department of Physics, Technische Universität München, Am Coulombwall 3, 85748 Garching, Germany

We will demonstrate the reversible transfer from optical polarization to the spin orientation of single carriers in semiconductor quantum dots. Following resonant excitation of the ground state exciton using circularly polarized light and selective charge separation in specially designed Schottky photodiode structures, we convert photon polarization into carrier spin orientation. After a time delay Δ t (=5ns to 1ms) the spin polarization of stored charges is tested by electrically neutralizing the dots and detecting the intensity and polarization state of the resulting electroluminescence signal. For electron storage samples, the EL is >80% circularly polarized at T = 1K with a helicity that directly reflects the optical excitation and vanishes following excitation with un-polarized light. Using such techniques, we have recently measured the electron spin T1 and its dependence on lattice temperature and magnetic field. It is shown to be extremely long (>25ms at 1K), decreasing with magnetic field with a clear B⁻⁵ exponent, demonstrating that spin flip at low temperatures is mediated by SO mixing of the Zeeman levels by single piezoelectric phonons. Electron spin dynamics will be contrasted with hole storage samples and prospects for optical single dot spin readout will be given.