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Phys. Rev. B 63, 205309 (2001) [5 pages]

Spin spectroscopy of dark excitons in CdSe quantum dots to 60 T

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E. Johnston-Halperin and D. D. Awschalom
Department of Physics, University of California, Santa Barbara, California 93106

S. A. Crooker
National High Magnetic Field Lab, MS E536, Los Alamos, New Mexico 87545

Al. L. Efros and M. Rosen
Nanostructure Optics Section, Naval Research Laboratory, Washington, D.C. 20375

X. Peng and A. P. Alivisatos
Department of Chemistry, University of California, Berkley, California 94720

Received 8 November 2000; published 24 April 2001

Polarization-resolved magnetophotoluminescence spectroscopy is used to study exciton spin states in 40–80 Å diameter chemically synthesized CdSe quantum dots (QDs) at temperatures T=1.2–50K. The spin polarization is found not to saturate in magnetic fields to 60 T and time-resolved studies indicate a thermal population of exciton states. A simple model incorporating the angle-dependent Zeeman splitting and bright-dark level mixing in these randomly oriented quantum dots is constructed in quantitative agreement with the data. Fits using this model yield a dark exciton g factor of ∼0.9 at T=1.45K, which is independent of QD diameter and exhibits a surprising increase with increasing temperature.

© 2001 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.63.205309
DOI:
10.1103/PhysRevB.63.205309
PACS:
73.21.-b, 78.66.-w
 
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