Abstract
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.
| Original language | English |
|---|---|
| Article number | 067403 |
| Journal | Physical Review Letters |
| Volume | 105 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - Aug 4 2010 |
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ASJC Scopus subject areas
- Physics and Astronomy(all)
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Revealing the exciton fine structure of PbSe nanocrystal quantum dots using optical spectroscopy in high magnetic fields. / Schaller, Richard D; Crooker, S. A.; Bussian, D. A.; Pietryga, J. M.; Joo, J.; Klimov, Victor I.
In: Physical Review Letters, Vol. 105, No. 6, 067403, 04.08.2010.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Revealing the exciton fine structure of PbSe nanocrystal quantum dots using optical spectroscopy in high magnetic fields
AU - Schaller, Richard D
AU - Crooker, S. A.
AU - Bussian, D. A.
AU - Pietryga, J. M.
AU - Joo, J.
AU - Klimov, Victor I
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
VL - 105
JO - Physical Review Letters
JF - Physical Review Letters
SN - 0031-9007
IS - 6
M1 - 067403
ER -