Optical probing of spin fluctuations of a single magnetic atom

TL;DR

This paper demonstrates a method to probe and measure the spin fluctuations of a single magnetic atom in a quantum dot through photoluminescence analysis, revealing spin dynamics and relaxation mechanisms.

Contribution

It introduces a phenomenological model and experimental approach to quantify spin fluctuations and relaxation times of a single magnetic atom in a semiconductor quantum dot.

Findings

Photon correlation measurements reveal signatures of spin fluctuations.

The model allows measurement of spin dynamics at zero magnetic field.

Spin relaxation times are consistent with spin-exchange mechanisms.

Abstract

We analyzed the photoluminescence intermittency generated by a single paramagnetic spin localized in an individual semiconductor quantum dot. The statistics of the photons emitted by the quantum dot reflect the quantum fluctuations of the localized spin interacting with the injected carriers. Photon correlation measurements which are reported here reveal unique signatures of these fluctuations. A phenomenological model is proposed to quantitatively describe these observations, allowing a measurement of the spin dynamics of an individual magnetic atom at zero magnetic field. These results demonstrate the existence of an efficient spin relaxation channel arising from a spin-exchange with individual carriers surrounding the quantum dot. A theoretical description of a spin-flip mechanism involving spin exchange with surrounding carriers gives relaxation times in good agreement with the measured dynamics.