Auger and spin dynamics in a self-assembled quantum dot

Abstract

The Zeeman-split spin states of a single quantum dot can be used together with its optical trion transitions to form a spin-photon interface between a stationary (the spin) and a flying (the photon) quantum bit. Besides long coherence times of the spin state itself, the limiting decoherence mechanisms of the trion states are of central importance. We investigate here in time-resolved resonance fluorescence the electron and trion dynamics in a single self-assembled quantum dot in an applied magnetic field of up to B = 10 T. The quantum dot is only weakly coupled to an electron reservoir with tunneling rates of about 1 ms −1 . Using this sample structure, we can measure, in addition to the spin-flip rate of the electron and the spin-flip Raman rate of the trion transition, the Auger recombination process, that scatters an Auger electron into the conduction band. The Auger effect destroys the radiative trion transition and leaves the quantum dot empty until an electron tunnels from the reservoir into the dot. The Auger recombination rate decreases by a factor of three from γ A = 3 µs −1 down to 1 µs −1 in an applied magnetic field of 10 T in Faraday geometry. The combination of an Auger recombination event with subsequent electron tunneling from the reservoir can flip the electron spin and thus constitutes a previously unaccounted mechanism that limits spin coherence, an important resource for quantum technologies.

Epitaxial quantum dots: a semiconductor launchpad for photonic quantum technologies

“…Coulomb interactions between electrons result in the Auger process [386,387] and radiative Auger process [388,389] . The radiative Auger process exists in both photon emission and absorption, in analogy to a Raman transition.…”