A hole-Cr${}^{+}$ nano-magnet in a semiconductor quantum dot

Abstract

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 3$d$ shell of the atom. We study the dynamics of the nano-magnet formed by the hole-Cr${}^{+}$ exchange interaction. The ferromagnetic ground states with M${}_z$=$\pm$4 can be controlled by resonant optical pumping and a spin relaxation time in the 20 $\mu$s range is obtained at T=4.2 K. This spin memory at zero magnetic field is limited by the interaction with phonons.

References in corpus (7)

• Defect Energy Levels in Density Functional Calculations: Alignment and Band Gap Problem
• Optically probing the fine structure of a single Mn atom in an InAs quantum dot
• Magneto-optics of excitons interacting with magnetic ions in CdSe/CdMnS colloidal nanoplatelets
• Dynamics of a Mn spin coupled to a single hole confined in a quantum dot
• Influence of non-equilibrium phonons on the spin dynamics of a single Cr atom
• Optical control of an individual Cr spin in a semiconductor quantum dot
• Charge fluctuations of a Cr atom probed in the optical spectra of a quantum dot