Spin properties of charged single Mn‐doped quantum dots

Abstract

The optical properties of individual quantum dots doped with a single Mn atom and charged with a single carrier (electron or hole) are analyzed. The emission of the neutral, positively charged and negatively charged excitons coupled with a single magnetic atom are observed in the same quantum dot. The spectrum of the charged excitons in interaction with the Mn atom shows a rich pattern attributed to a strong anisotropy of the hole -Mn exchange interaction slightly perturbed by a small valence band mixing. For the positively charged exciton, the emission pattern shows that the different spin states of the hole -Mn complex remain split in the final state after the exciton recombination. This opens the possibility of storing information on a single carrier spin on a long time scale in the absence of external magnetic field.Precise control of electronic spins in semiconductors should lead to the development of novel electronic systems based on the carriers' spin degree of freedom. Magnetic semiconductor quantum dots (QDs), where carriers can strongly interact with the magnetic atoms, hold particular promise as building blocks for such spin-based systems. They have been proposed as single-spin filters or single spin aligners in quantum information processing devices [1,2]. Developing such devices requires, however, the ability to detect and manipulate individual spins. QDs based on II-VI semiconductor compounds offer the unique possibility of tuning independently the incorporation of charge carriers and the magnetic doping. Manganese is indeed introduced into the crystal matrix as an isoelectronic substitution of the II element, with 3d 5 electronic configuration (S = 5/2). This provides a way to study precisely the interaction between injected carriers and the localized magnetic ions. Recently, CdTe/ZnTe QDs doped with single manganese atoms were realized, making it possible to detect optically the quantum states of a single spin S = 5/2 [3].In this work we present the emission features of charged QDs doped with a single Mn atom. These QDs are the unique system allowing to probe the interaction between an individual magnetic atom and a single confined electron or hole. A photo-depletion mechanism is used to control the charge state of individual Mn-doped QDs. The experimental survey of the neutral exciton X (1 electron (e) and 1 hole (h)) and charged excitons X -(2e, 1h) and X + (1e, 2h) shows that the Mn spin is very sensitive to the number of electrons and holes in both the excited and the ground state of the dot [4,5]. Measurements prove that even if a high anisotropy of the (h, Mn) complex is conserved along the growth axis, heavylight hole mixing induced by inhomogeneous relaxation of strains have important effects on its energy structure.

Ab initiocharacterization of transition-metal-doped Si nanocrystals

“…4 In the current focus of theoretical and experimental studies there are Mn-doped II-VI and III-V semiconductors but also Ge nanocrystals. [11][12][13][14][15][16] TM doping of Si nanostructures becomes also interesting, as recently shown for Si nanowires. 17 Those quasi-one-dimensional structures exhibit an half-metallic character under certain conditions.…”

Magnetic interaction in pairwise Mn-doped Si nanocrystals

“…Important examples are TM-doped nanocrystals ͑NCs͒ with three-dimensional electronic confinement. [3][4][5][6] Their novel magnetic properties make them attractive to develop nanoscale magnetic species for spintronics. 7 Prototypical examples are prepared by incorporation of Mn 2+ ions with the largest magnetic moment of the 3d shell into II-VI semiconductor nanocrystals.…”

“…7 Prototypical examples are prepared by incorporation of Mn 2+ ions with the largest magnetic moment of the 3d shell into II-VI semiconductor nanocrystals. [3][4][5][6] Such doped nanocrystalline systems have also been studied theoretically. [7][8][9] Meanwhile such studies also exist for Mn-doped III-V semiconductor nanocrystals 8,10-12 and the incorporation of TM atoms into group-IV ͑Si or Ge͒ nanocrystals.…”

Magnetoluminescence of a CdTe Quantum Dot with a Single Manganese Ion in Voigt Configuration

“…Figure 1 presents the spectrum of the QD chosen for further measurements. We can clearly observe the characteristic six-line pattern originating from the neutral exciton (X) recombination in the presence of a Mn atom [7,8]. These lines correspond to the six possible projections of the Mn spin on the quantization axis.…”