Imaging the Electron Wave Function in Self-Assembled Quantum Dots

Вдовин, Е. Е.; Levin, A. D.; Patanè, A.; Eaves, L.; Main, P. C.; Khanin, Yu. N.; Dubrovskiĭ, Yu. V.; Henini, M.; Hill, G.

doi:10.1126/science.290.5489.122

Cited by 177 publications

(128 citation statements)

References 22 publications

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“…These more detailed curves taken at 0 and 4T clearly show that the feature actually has a complex structure, consisting of four distinct peaks, which evolve with the magnitude of the applied magnetic field. We verified that the evolution of the features does not appreciably depend on the direction of the magnetic field, indicating that the magnetic response of the system cannot be associated with artefacts such as two dimensional states in the injector or wetting layer [5,11,12,13], and that it must be a property of the dot or the barrier. We also verified that the sample does not exhibit any magnetic hysteresis.…”

mentioning

confidence: 59%

“…From the size of the pillars, and the typical density of the dots, one would expect some million dots within our device. However, despite this number, transport through similar III-V SADRTDs is usually dominated by only a few dots that come into resonance at lower bias voltages [11,12,13]. We therefore interpret the low bias transport through our sample as corresponding to electrons tunnelling from the injector into a single quantum dot and out of the dot into the collector as schematically depicted in Fig.…”

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confidence: 99%

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

et al. 2006

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“…Another example relates to a specific density of states in the classical region after the tunneling barrier. A state of an electron, influenced by the magnetic field, may fit better that density of states and this results in increase of tunneling rate [16].…”

Section: Introductionmentioning

confidence: 99%

Cyclotron enhancement of tunneling

Medvedeva

Larkin²,

Ujevic³

et al. 2008

Phys. Rev. B

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A state of an electron in a quantum wire or a thin film becomes metastable, when a static electric field is applied perpendicular to the wire direction or the film surface. The state decays via tunneling through the created potential barrier. An additionally applied magnetic field, perpendicular to the electric field, can increase the tunneling decay rate for many orders of magnitude. This happens, when the state in the wire or the film has a velocity perpendicular to the magnetic field. According to the cyclotron effect, the velocity rotates under the barrier and becomes more aligned with the direction of tunneling. This mechanism can be called cyclotron enhancement of tunneling.

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“…18 A major challenge for developers of quantum devices is to obtain information about the electronic wavefunction of quantum states in the interior of devices. Suggested techniques include a grown-in potential perturbation, 27 changing the phase with the vector potential of an applied magnetic field, 28 and a potential perturbation from an external probe. 29 In this paper, we propose an imaging technique to measure the energy levels of an electron inside a nanostructure and to extract the density profile of the electronic wavefunctions using a cooled SPM.…”

Section: Introductionmentioning

confidence: 99%

Extracting the density profile of an electronic wave function in a quantum dot

Boyd

Westervelt

2011

Phys. Rev. B

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The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Coulomb blockade spectroscopy. When the tip is close to the nanowire dot, it dents the wavefunction Ψ(x) of the quantum state, changing the electron's energy by an amount proportional to |Ψ(x)| 2 . By recording the change in energy as the SPM tip is moved along the length of the dot, the density profile of the electronic wavefunction can be found along the length of the quantum dot.2

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Imaging the Electron Wave Function in Self-Assembled Quantum Dots

Cited by 177 publications

References 22 publications

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

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

Cyclotron enhancement of tunneling

Extracting the density profile of an electronic wave function in a quantum dot

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