TY - JOUR
T1 - Revealing the exciton fine structure of PbSe nanocrystal quantum dots using optical spectroscopy in high magnetic fields
AU - Schaller, R. D.
AU - Crooker, S. A.
AU - Bussian, D. A.
AU - Pietryga, J. M.
AU - Joo, J.
AU - Klimov, V. I.
N1 - Copyright:
Copyright 2010 Elsevier B.V., All rights reserved.
PY - 2010/8/4
Y1 - 2010/8/4
N2 - We measure the photoluminescence lifetime τ of excitons in colloidal PbSe nanocrystals (NCs) at low temperatures to 270 mK and in high magnetic fields to 15 T. For all NCs, τ increases sharply below 10 K but saturates by 500 mK. In contrast to the usual picture of well-separated "bright" and "dark" exciton states (found, e.g., in CdSe NCs), these dynamics fit remarkably well to a system having two exciton states with comparable-but small-oscillator strengths that are separated by only 300-900μeV depending on NC size. Importantly, magnetic fields reduce τ below 10 K, consistent with field-induced mixing between the two states. Magnetic-circular dichroism studies reveal exciton g factors from 2-5, and magnetophotoluminescence shows >10% circularly polarized emission.
AB - We measure the photoluminescence lifetime τ of excitons in colloidal PbSe nanocrystals (NCs) at low temperatures to 270 mK and in high magnetic fields to 15 T. For all NCs, τ increases sharply below 10 K but saturates by 500 mK. In contrast to the usual picture of well-separated "bright" and "dark" exciton states (found, e.g., in CdSe NCs), these dynamics fit remarkably well to a system having two exciton states with comparable-but small-oscillator strengths that are separated by only 300-900μeV depending on NC size. Importantly, magnetic fields reduce τ below 10 K, consistent with field-induced mixing between the two states. Magnetic-circular dichroism studies reveal exciton g factors from 2-5, and magnetophotoluminescence shows >10% circularly polarized emission.
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U2 - 10.1103/PhysRevLett.105.067403
DO - 10.1103/PhysRevLett.105.067403
M3 - Article
AN - SCOPUS:77955336528
VL - 105
JO - Physical Review Letters
JF - Physical Review Letters
SN - 0031-9007
IS - 6
M1 - 067403
ER -