Hyperfine interaction mediated exciton spin relaxation in (In,Ga)As quantum dots

Abstract

The population dynamics of dark and bright excitons in (In,Ga)As/GaAs quantum dots is studied by two-color pump-probe spectroscopy in an external magnetic field. With the field applied in Faraday geometry and at T<20 K, the dark excitons decay on a ten nanoseconds time scale unless the magnetic field induces a resonance with a bright exciton state. At these crossings their effective lifetime is drastically shortened due to spin flips of either electron or hole by which the dark excitons are converted into bright ones. Due to the quasielastic character we attribute the origin of these flips to the hyperfine interaction with the lattice nuclei. We compare the exciton spin relaxation times in the two resonances and find that the spin flip involving an electron is approximately 25 times faster than the one of the hole. A temperature increase leads to a considerable, nonmonotonic decrease of the dark exciton lifetime. Here phonon-mediated spin flips due to the spin-orbit interaction gradually become more important.

expanded version (cf. sections III.C and III.D)

References in corpus (11)

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• Spin relaxation and decoherence of holes in quantum dots
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• Direct measurement of the hole-nuclear spin interaction in single quantum dots
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• Geometrical spin dephasing in quantum dots

Cited by in corpus (6)

• Tracking Dark Excitons with Exciton Polaritons in Semiconductor Microcavities
• Dynamic nuclear polarization in InGaAs/GaAs and GaAs/AlGaAs quantum dots under non-resonant ultra-low power optical excitation
• Spin-orbit induced hole spin relaxation in InAs and GaAs quantum dots
• Hyperfine coupling of hole and nuclear spins in symmetric GaAs quantum dots
• Dephasing of InAs quantum dot p-shell excitons using two-dimensional coherent spectroscopy
• Phonon-assisted carrier tunneling in coupled quantum dot systems with hyperfine-induced spin flip