Exciton magnetic polaron in semimagnetic semiconductor nanocrystals

Bhattacharjee, A. K.; Guillaume, C. Benoît à la

doi:10.1103/physrevb.55.10613

Cited by 108 publications

(104 citation statements)

References 30 publications

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“…presumably with smaller average sizes. As this photo-induced magnetization is a result of the formation of spin-aligned EMPs, this may suggest that the polarons are more stable in smaller QDs [26]. We also observe almost two times stronger polarization of the emission for the ensemble of QDs with smaller average Mn concentration.…”

supporting

confidence: 60%

Optical studies of zero-field magnetization of CdMnTe quantum dots: Influence of average size and composition of quantum dots

Gurung

Maćkowski

Jackson

et al. 2004

Journal of Applied Physics

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We show that through the resonant optical excitation of spin-polarized excitons into CdMnTe magnetic quantum dots, we can induce a macroscopic magnetization of the Mn impurities. We observe very broad (4 meV linewidth) emission lines of single dots, which are consistent with the formation of strongly confined exciton magnetic polarons. Therefore we attribute the optically induced magnetization of the magnetic dots results to the formation of spin-polarized exciton magnetic polarons. We find that the photo-induced magnetization of magnetic polarons is weaker for larger dots which emit at lower energies within the QD distribution. We also show that the photo-induced magnetization is stronger for quantum dots with lower Mn concentration, which we ascribe to weaker Mn-Mn interaction between the nearest neighbors within the dots. Due to particular stability of the exciton magnetic polarons in QDs, where the localization of the electrons and holes is comparable to the magnetic exchange interaction, this optically induced spin alignment persists to temperatures as high as 160 K.

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supporting

confidence: 60%

Optical studies of zero-field magnetization of CdMnTe quantum dots: Influence of average size and composition of quantum dots

Gurung

Maćkowski

Jackson

et al. 2004

Journal of Applied Physics

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“…The interaction of this total net spin with the spin of Mn ions induces an effective ferromagnetic Mn-Mn interaction. This can be seen by considering the total Hamiltonian of the electronic and Mn system [7,8,15,16]:…”

Section: Gaasmentioning

confidence: 99%

Remanent Zero Field Spin Splitting of Self-Assembled Quantum Dots in a Paramagnetic Host

et al. 2006

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A key element in the emergence of a full spintronics technology is the development of voltage controlled spin filters to selectively inject carriers of desired spin into semiconductors. We previously demonstrated a prototype of such a device using a II-VI dilute-magnetic semiconductor quantum well which, however, still required an external magnetic field to generate the level splitting. Recent theory suggests that spin selection may be achievable in II-VI paramagnetic semiconductors without external magnetic field through local carrier mediated ferromagnetic interactions. We present the first experimental observation of such an effect using non-magnetic CdSe self-assembled quantum dots in a paramagnetic (Zn,Be,Mn)Se barrier.PACS numbers: 72.25. Dc, 85.75.Mm Nanomagnetics has over the past few years produced a series of fascinating and often unanticipated phenomena. To name a few, molecular magnets exhibit quantum tunnelling of the magnetization[1], magnetic atoms on a surface exhibit giant magnetic anisotropies [2], and magnetic domain walls are being harnessed as data carriers [3]. Here, we report on another remarkable phenomenon: self-assembled quantum dots, fabricated from II-VI dilute magnetic semiconductors (DMS) that macroscopically exhibit paramagnetism, possess a remanent magnetization at zero external field. This allows us to operate the dots as voltage controlled spin filters, capable of spin-selective carrier injection and detection in semiconductors. Such spin filter devices could provide a key element in the emergence of a full spintronics technology [4]. We present the first experimental observation of such a device using an approach based on the incorporation of non-magnetic CdSe self assembled quantum dots (SADs) in paramagnetic (Zn,Be,Mn)SeWe previously demonstrated a prototype of such a spin filter using a II-VI DMS-based resonant tunnelling diode [5]. However, while that device was tuned by a bias voltage, the spin filtering mechanism still required an external magnetic field. Moreover, ferromagnetic III-V semiconductors like (Ga,Mn)As are not suitable for resonant tunnelling devices due to the short mean free path of holes [6]. Recent theoretical works [7,8,9] have suggested that spin selection may be achievable in II-VI DMS without any external magnetic field by creating localized carriers that might mediate a local ferromagnetic interaction between nearby Mn atoms.Our sample is an MBE-grown all-II-VI resonant tunnelling diode (RTD) structure consisting of a single 9 nm thick semi-magnetic Zn 0.64 Be 0.3 Mn 0.06 Se tunnel barrier, sandwiched between gradient doped Zn 0.97 Be 0.03 Se injector and collector. Embedded within the barrier are 1.3 monolayers of CdSe. The lattice mismatch between the CdSe and the Zn 0.64 Be 0.3 Mn 0.06 Se induces a strain in the CdSe material, which is relaxed by the formation of isolated CdSe dots [10]. The full layer stack is given in Fig. 1. Standard optical lithography techniques were used to pattern the structure into 100 µm square pillars, and contacts wer...

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“…12,13,38 In this model, the particle's ground-state carrier density distribution is given by the square of a zeroth order spherical Bessel function of the first kind (eq 6), where a is the well radius, equated here with the QD radius.…”

Section: E Mn 2+ Position Concentration and Qd Size The Dependencmentioning

confidence: 99%

“…[1][2][3][32][33][34][35][36] Whereas the general features of sp-d exchange appear to translate across length scales, specific contrasts have been emphasized in some cases. 12,13,[36][37][38][39][40] Most prominently, a strong quantum-confinement-induced change in the fundamental nature of the conduction-band-electron ( e CB − ) -Mn 2+ exchange (s-d exchange) interaction has been described both theoretically 36,37 and experimentally. 37,[41][42][43][44][45] According to k·p-model descriptions of Mn at finite k vectors.…”

Section: Introductionmentioning

confidence: 99%

“…In diluted magnetic semiconductors (DMSs), exchange interactions between localized magnetic impurities and delocalized charge carriers give rise to various technologically important effects including giant spin splittings of the semiconductor band structure, [1][2][3] exciton spin polarization, [4][5][6][7] spin-polarized electrical currents, 8,9 excitonic magnetic polarons, [10][11][12][13][14][15][16] and carrier-controlled magnetism. [17][18][19][20] Within the past decade, attention has turned to magnetically doped semiconductor nanostructures like colloidal or self-assembled DMS quantum dots (QDs), 10,[21][22][23] motivated in part by potential quantum optics or information processing technologies.…”

Section: Introductionmentioning

confidence: 99%

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Orbital pathways for Mn2+-carriersp−dexchange in diluted magnetic semiconductor quantum dots

et al. 2011

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Abstract. Manganese-carrier magnetic exchange interactions in strongly quantum confined -conduction-band-electron interaction is described well using the recently proposed ferromagnetic kinetic s-s exchange pathway. Antiferromagnetic kinetic s-d exchange interactions previously proposed to become dominant in quantum confined diluted magnetic semiconductors (DMSs) have been evaluated quantitatively by both DFT and perturbation theory and are found to be weak compared to the ferromagnetic s-s interaction, even in these strongly confined QDs. The magnitudes of the mean-field exchange parameters are found to be nearly independent of quantum confinement over this range of QD diameters, and the dominant orbital pathways are not fundamentally altered by quantum confinement.i.

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Exciton magnetic polaron in semimagnetic semiconductor nanocrystals

Cited by 108 publications

References 30 publications

Optical studies of zero-field magnetization of CdMnTe quantum dots: Influence of average size and composition of quantum dots

Optical studies of zero-field magnetization of CdMnTe quantum dots: Influence of average size and composition of quantum dots

Remanent Zero Field Spin Splitting of Self-Assembled Quantum Dots in a Paramagnetic Host

Orbital pathways for Mn2+-carriersp−dexchange in diluted magnetic semiconductor quantum dots

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