Probing the Spin State of a Single Magnetic Ion in an Individual Quantum Dot

Abstract

The magnetic state of a single magnetic ion (Mn2+) embedded in an individual quantum dot is optically probed using microspectroscopy. The fine structure of a confined exciton in the exchange field of a single Mn2+ ion (S=5/2) is analyzed in detail. The exciton-Mn2+ exchange interaction shifts the energy of the exciton depending on the Mn2+ spin component and six emission lines are observed at zero magnetic field. Magneto-optic measurements reveal that the emission intensities in both circular polarizations are controlled by the Mn2+ spin distribution imposed by the exchange interaction with the exciton, the magnetic field, and an effective manganese temperature which depends on both the lattice temperature and the density of photocreated carriers. Under magnetic field, the electron-Mn interaction induces a mixing of the bright and dark exciton states.

Optical Properties of Manganese-Doped Individual CdTe Quantum Dots

“…6b. The fitted Landé factors of the electron (g e = −1.1), the hole (g h = 0.3) and the Mn atom (g Mn = 2.0), the splitting between J z = ±1 and J z = ±2 excitons (= 1 meV) and the diamagnetic factor (γ = 2.45 µeV T −2 ) agree well with previous works [8,14]. Parameters δ 2 and δ Mn were adjusted to fit the zero field data, as explained earlier.…”

“…Since the dipolar interaction operator does not affect the Mn d electrons, the final states involve only the Mn 2+ states |S z Mn with the same spin component [14]. In this framework, at zero magnetic field, the QD emission presents a fine structure composed of six doubly degenerate transitions roughly equally spaced in energy …”

“…These lines correspond to the radiative ("bright") exciton states J z = ±1 coupled to the six spin components of the Mn atom (S = 5/2). Analysis of the line intensities gives the occupation probability of the six Mn spin states [14]. The three low intensity lines on the low energy side of the structure (Fig.…”

Coherent manipulation of a single magnetic atom using polarized single electron transport in a double quantum dot

“…These magnetic atoms have six quantized spin states |m , with corresponding eigenvalues m = −5/2,−3/2,−1/2,1/2,3/2,5/2. 4 In Fig.2(a), initial state |ψ M (0) of the magnetic atom is set to be any of the six quantized states. In all cases the magnetic atom is driven to the final state |5/2 .…”

“…In dilute II-VI semiconductor quantum dots (QD), interaction between a manganese (Mn) atom and a carrier can be effectively described with the sp − d exchange interaction. [4][5][6] Based on the impurity-carrier coupling, electrical control of the single magnetic atom is feasible by injecting different charges in the magnetic atom doped QD. 6 As shown both in experiment 2 and theory, 7 electrons can directly tunnel through a Mn atom by taking its spin states.…”