Single vanadium ion magnetic dopant in an individual CdTe/ZnTe quantum dot

Abstract

We present the basic properties of a new physical system: an individual V2+ ion embedded into an individual quantum dot. The system is realized utilizing molecular beam epitaxy and it is observed using a low-temperature polarization-resolved magneto-photoluminescence. The nature of the system is confirmed by observation of the excitonic lines split due to the interactions of a vanadium ion with carriers confined in a CdTe/ZnTe quantum dot. Observed data are explained by the numerical modeling which includes s,p-d exchange interaction, Zeeman splitting of the exciton and the ion, diamagnetic shift, and the presence of shear strain within the quantum dot. The fundamental state of vanadium exhibits a spin +/- 1/2 making this system a textbook localized qubit.

Figures (4)

• Figure 1: Vanadium as a dopant in the epitaxial QDs made of CdTe and ZnTe. a) Scheme of the structure grown by MBE. b) Ion of vanadium in the tetrahedral symmetry of the closest neighbors of the tellurium anions. c) Scheme of the energy levels splitting by the influence of the crystal lattice, Jahn-Teller effect, spin-orbit coupling, and Zeeman effect. Atomic term symbols after wanad_cdte_christmann.
• Figure 2: The first report of the QD with a solitary V$^{2+}$ dopant. The measurement of polarization-resolved magnetospectroscopy revealed neutral exciton (X), biexciton (XX), and negative trion (X$^{-}$) of a CdTe QD consisting of an ion of vanadium. The experiment was performed at a temperature of $1.6$ K.
• Figure 3: Excitonic complexes of a QD consisting V$^{2+}$: comparison of experimental (a, c, e) and calculated (b, d, f) results. The spin Hamiltonian model included exange interaction between excitons and ion, Zeeman splitting of the exciton and the ion, diamagnetic shift, and the shear strain influence on the valence band. Final parameters of the Hamiltonian: $\Delta_{s{,}p-d} = 0.4$ meV, $\delta_\mathrm{X} = 0.025$ meV, $g_\mathrm{V} = 2$, $g_\mathrm{X} = 2.7$, $\gamma = 0.0015\,\frac{\mu \textnormal{eV}}{\textnormal{T}^2}$, $\Delta_{p-d}\xi = 0.0525$ meV, $T = 30$ K, $k = 0.0862\,\frac{\textnormal{meV}}{\textnormal{K}}$, $\mu _b = 5.788\times10^{-2}\,\frac{\textnormal{meV}}{\textnormal{T}}$.
• Figure 4: Energy level scheme of the XX-X cascade of the QD with single vanadium dopant. The origin of the anticrossings observed in the magnetic field $B_\mathrm{ac}$ is located in the X, in the splitting of the state with the same orientation of the hole spin, but a different orientation of the spin of vanadium (dark blue lines). Optical transitions in $\sigma^-$ polarization are marked with light blue arrows, while orange arrows represent optical transitions observed in $\sigma^+$ polarization.