We study a new diluted magnetic semiconductor system based on the spin of the ionized acceptor Cr+. We show that the negatively charged Cr+ ion, an excited state of the Cr in II-VI semiconductor, can be stable when inserted in a CdTe quantum dot (QD). The Cr+ attracts a heavy-hole in the QD and form a stable hole-Cr+ complex. Optical probing of this system reveals a ferromagnetic coupling between heavy-holes and Cr+ spins. At low temperature, the thermalization on the ground state of the hole-Cr+ system with parallel spins prevents the optical recombination of the excess electron on the 3d shell of the atom. We study the dynamics of the nano-magnet formed by the hole-Cr+ exchange interaction. The ferromagnetic ground states with Mz=±4 can be controlled by resonant optical pumping and a spin relaxation time in the 20 μs range is obtained at T=4.2 K. This spin memory at zero magnetic field is limited by the interaction with phonons.
Cite
@article{arxiv.2107.03192,
title = {A hole-Cr$^{+}$ nano-magnet in a semiconductor quantum dot},
author = {V. Tiwari and M. Arino and S. Gupta and M. Morita and T. Inoue and D. Caliste and P. Pochet and H. Boukari and S. Kuroda and L. Besombes},
journal= {arXiv preprint arXiv:2107.03192},
year = {2021}
}