Time- and Polarization-Resolved Optical Spectroscopy of Colloidal CdSe Nanocrystal Quantum Dots in High Magnetic Fields

In an effort to elucidate the spin degrees of freedom in colloidal semiconductor nanocrystal quantum dots, we report on a series of static and time-resolved photoluminescence measurements of colloidal CdSe quantum dots in ultra-high magnetic fields up to 45 Tesla

Madalina Furis; Jennifer A. Hollingsworth; Victor I. Klimov; Scott A. Crooker

2005

Scholarcy highlights

  • The remarkable optical properties of colloidal semiconductor nanocrystal quantum dots have attracted considerable interest across the chemical, physical, and materials science communities in recent years
  • In an effort to elucidate the spin degrees of freedom in colloidal semiconductor nanocrystal quantum dots, we report on a series of static and time-resolved photoluminescence measurements of colloidal CdSe quantum dots in ultra-high magnetic fields up to 45 Tesla
  • The spin polarization of excitons in colloidal CdSe NQDs is studied via polarization analysis of the static and time-resolved PL
  • High magnetic fields lead to a significant degree of circularly polarized PL emission up to 70%, which can be modeled by averaging emission from a thermal distribution between J = +2 and
  • Time-resolved studies show that magnetic field induced mixing of dark and bright exciton states leads to markedly reduced exciton lifetimes, quite similar to the effects of thermal excitation from dark to bright exciton states due to increased temperature
  • Thermalization of photoinjected excitons between the Zeeman-split J = ±2 dark exciton states occurs on sub-nanosecond timescales, after which the degree of spin polarization remains constant throughout the exciton lifetime
  • This constant degree of spin polarization is robust even in the presence of strong inter-dot coupling due to Forster exciton transfer processes

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