We analyse the influence of optically generated non-equilibrium phonons on the spin relaxation and effective spin temperature of an individual Cr atom inserted in a quantum dot. Using a three pulses pump-probe technique, we show that the spin relaxation measured in resonant optical pumping experiments strongly depends on the optical excitation conditions. We observe for an isolated Cr in the dark a heating time shorter than a few hundreds ns after an initial high power non-resonant excitation pulse. A cooling time larger than a few tens of μs, independent on the excitation, is obtained in the same experimental conditions. We show that a tunable spin-lattice coupling dependent on the density of non-equilibrium phonons can explain the observed dynamics. Low energy excitation conditions are found where the Cr spin states Sz=±1 can be efficiently populated by a non-resonant optical excitation, prepared and read-out by resonant optical pumping and conserved in the dark during a few μs.
@article{arxiv.1911.07639,
title = {Influence of non-equilibrium phonons on the spin dynamics of a single Cr atom},
author = {V. Tiwari and K. Makita and M. Arino and M. Morita and S. Kuroda and H. Boukari and L. Besombes},
journal= {arXiv preprint arXiv:1911.07639},
year = {2020}
}