Article abstract
Nature Physics 5, 758 - 763 (2009)
Published online: 16 August 2009 | doi:10.1038/nphys1363
Subject Categories: Condensed-matter physics | Electronics, photonics and device physics
Confluence of resonant laser excitation and bidirectional quantum-dot nuclear-spin polarization
C. Latta1,6, A. Högele1,6,7, Y. Zhao2,7, A. N. Vamivakas2, P. Maletinsky1, M. Kroner1, J. Dreiser1, I. Carusotto3, A. Badolato4, D. Schuh5, W. Wegscheider5,7, M. Atature2 & A. Imamoglu1
Abstract
Resonant laser scattering along with photon correlation measurements established the atom-like character of quantum dots. Here, we show that for a wide range of experimental parameters it is impossible to isolate elementary quantum-dot excitations from a strong influence of nuclear spins; the absorption lineshapes at magnetic fields exceeding 1 T indicate that the nuclear spins get polarized by an amount that ensures locking of the quantum-dot resonance to the incident laser frequency. In stark contrast to earlier experiments, this nuclear-spin polarization is bidirectional, allowing the combined electron–nuclear-spin system to track the changes in laser frequency dynamically on both sides of the resonance. This unexpected feature stems from a competition between two spin-pumping processes that attempt to polarize nuclear spins in opposite directions. We find that the confluence of laser excitation and nuclear-spin polarization suppresses the fluctuations in resonant absorption. A master-equation analysis suggests narrowing of the nuclear-spin distribution, pointing to applications in quantum information processing.
- Institute of Quantum Electronics, ETH-Zurich, CH-8093, Zurich, Switzerland
- Cavendish Laboratory, University of Cambridge, JJ Thomson Ave, Cambridge CB3 0HE, UK
- CNR-INFM BEC Center and Dipartimento di Fisica, Università di Trento, via Sommarive 14, I-38050 Povo, Trento, Italy
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Regensburg, Germany
- These authors contributed equally to this work
- Present address: Ludwig-Maximilians-Universität München, Fakultät für Physik und CeNS, Geschwister-Scholl-Platz 1, 80539 München, Germany (A.H.). Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Philosophenweg 12, Heidelberg 69120, Germany (Y.Z.); Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland (W.W.)
Correspondence to: A. Imamoglu1 e-mail: imamoglu@phys.ethz.ch
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