Electrical Control of a Single Mn Atom in a Quantum Dot

We report on the reversible electrical control of the magnetic properties of a single Mn atom in an individual quantum dot. Our device permits us to prepare the dot in states with three different electric charges, 0, $+1e$, and $-1e$ which result in dramatically different spin properties, as revealed by photoluminescence. Whereas in the neutral configuration the quantum dot is paramagnetic, the electron-doped dot spin states are spin rotationally invariant and the hole-doped dot spins states are quantized along the growth direction.

Figure 1

Color-scale plot of the photoluminescence intensity of a nonmagnetic QD (a) and a single Mn-doped QD (b) in a Schottky structure as a function of emission energy and bias voltage. The series of emission lines can be assigned to QD $s$-shell transitions, namely, the recombination of the neutral exciton ($X$), biexciton ($X^2$), positively charged exciton ($X^{+}$), and negatively charged exciton ($X^{-}$).

Figure 2

(a) Multichannel photoluminescence excitation spectra of a single Mn-doped QD at zero gate voltage. (b) Detail of the PL of a single Mn-doped QD under resonant excitation ($E_{\mathrm{ex}}=2147\mathrm{meV}$), nonresonant excitation ($E_{\mathrm{ex}}=2412\mathrm{meV}$), and both resonant and nonresonant excitation.

Figure 3

(a) Detail of the unpolarized emission spectrum of a negatively charged exciton ($X^{-}$) coupled with a Mn atom. (b) Scheme of the $\sigma +$ optical transitions of ($X^{-}$, Mn) and their respective PL intensity distribution (c).

Figure 4

Color-scale plot of the dependence of the PL of ($X^{-}$, Mn) (a) and ($X^{+}$, Mn) (b) on the direction of a linear analyzer, in the same QD. Three lines in the center of the structure are linearly polarized. (c) and (d) calculated linearly polarized PL spectra of ($X^{-}$, Mn) and ($X^{+}$, Mn) with exchange integrals $I_e$ and $I_h$ chosen to reproduce the overall splitting for $X^{+}$ and $X^{-}$ presented in (a) and (b). Transitions are arbitrarily broadened by $10\mu \mathrm{eV}$. The schemes in (c) and (d) show energy levels involved in ($X^{-}$, Mn) and ($X^{+}$, Mn) recombination with valence band mixing. The central inset presents the energy level scheme of the $h$-Mn system without and with valence band mixing (VBM).