Revealing the Exciton Fine Structure of PbSe Nanocrystal Quantum Dots Using Optical Spectroscopy in High Magnetic Fields

Journal Article · Wed Aug 04 04:00:00 EDT 2010 · Phys. Rev. Lett.

DOI:https://doi.org/10.1103/PhysRevLett.105.067403· OSTI ID:1065041

Schaller, Richard D. ^[1]; Crooker, Scott A. ^[2]; Bussian, David A. ^[1]; Pietryga, Jeffrey M. ^[1]; Joo, Jin ^[1]; Klimov, Victor I. ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. National High Magnetic Field Lab., Los Alamos, NM (United States)

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 300–900 μeV 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.

• Research Organization: Energy Frontier Research Centers (EFRC); Center for Advanced Solar Photophysics (CASP)
• Sponsoring Organization: USDOE SC Office of Basic Energy Sciences (SC-22)
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1065041
• Journal Information: Phys. Rev. Lett., Journal Name: Phys. Rev. Lett. Vol. 105
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

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