Mapping Exciton Spin States in CdSe Nanocrystals with Spin-Polarized, Resonant Photoluminescence Spectroscopy

ORAL

Abstract

We report on high-resolution, spin-polarized resonant photoluminescence (PL) studies of exciton spin states in CdSe nanocrystals in high magnetic fields up to 33 T. Optically allowed spin-up or spin-down ``bright'' (spin-1) excitons are resonantly pumped using a circularly-polarized, narrowband, tunable dye laser. Quasi-resonant PL from the optically forbidden ``dark'' (spin-2) excitons is analyzed as a function of polarization and magnetic field, allowing us to map the evolution of both ``dark'' and ``bright'' excitons with magnetic field. Strikingly, the PL develops a sharp, circularly- polarized ``spin flip-like'' peak for B $>$ 10 T, which we associate with the splitting of the "bright" exciton state. This energy splitting scales inversely with nanocrystal size and extrapolates to a finite value at zero magnetic fields. This large, zero-field splitting of the ``bright'' exciton (1-2 meV) likely originates from the anisotropy of the nanocrystal confining potential.

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Authors

  • Madalina Furis

  • Patrick Robbins

  • Todd Barrick

  • Scott Crooker

    • National High Magnetic Field Laboratory-Los Alamos
    • National High Magnetic Field Laboratory-Los Alamos National Laboratory, New Mexico, USA
    • Los Alamos National Laboratory

  • Serguei Goupalov

    • Los Alamos National Laboratory

  • Melissa Petruska

  • Victor Klimov

    • Los Alamos National Laboratory, New Mexico, USA
    • Los Alamos National Laboratory, Los Alamos, NM-87545
    • Los Alamos National Laboratory
    • Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545

  • Alexander Efros

    • Naval Research Laboratory, Washington DC, USA