Observation of spin splitting in single InAs self-assembled quantum dots in AlAs

Thornton, A.S.G.; Ihn, Thomas; Main, P. C.; Eaves, L.; Henini, M.

doi:10.1063/1.121832

Cited by 57 publications

(30 citation statements)

References 11 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.…”

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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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“…Unlike in bulk InAs the Landé factor of the quantum dots is positive. 7,23 As a consequence we identify the FES at lower bias voltage with tunneling of spin-↓ electrons. Performing a fit to the experimental data we obtain ␥ ↑ = 0.27, ␥ ↓ = 0.46, ␣ = 0.15, and ⌫ i = 0.36 K. Now, the FES from tunneling of electrons with spin ↓ ͑corresponding to the peak in the I-V curves at lower bias͒ can be isolated by subtracting the theoretical contribution from the other spin projection.…”

Section: Application To Tunneling Experimentsmentioning

confidence: 99%

Fermi-edge singularities in transport through quantum dots

et al. 2006

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We study the Fermi-edge singularity appearing in the current-voltage characteristics for resonant tunneling through a localized level at finite temperature. An explicit expression for the current at low temperature and near the threshold for the tunneling process is presented which allows to coalesce data taken at different temperatures to a single curve. Based on this scaling function for the current we analyze experimental data from a GaAs-AlAs-GaAs tunneling device with embedded InAs quantum dots obtained at low temperatures in high magnetic fields.

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“…In measurements on InAs-based two-dimensional electron systems, values from g * = −1 to g * = −13 have been found experimentally depending on magnetic field direction [18], quantum well width [15] and barrier composition [15,17] and gate tunability of g * has been demonstrated [17,19]. Investigations on self-assembled InAs QDs using magnetotunneling and capacitance spectroscopy have revealed anisotropic g-factors with values from +0.5 to +1.6 [20,21]. For WZ crystals both effective mass and g-factor are expected to be anisotropic and theoretical expression can be derived within k · p-theory [22,23].…”

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Tunable effectivegfactor in InAs nanowire quantum dots

et al. 2005

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We report tunneling spectroscopy measurements of the Zeeman spin splitting in InAs few-electron quantum dots. The dots are formed between two InP barriers in InAs nanowires with a wurtzite crystal structure which are grown using chemical beam epitaxy. The values of the electron g-factors of the first few electrons entering the dot are found to strongly depend on dot size. They range from close to the InAs bulk value in large dots |g * | = 13 down to |g * | = 2.3 for the smallest dots.PACS numbers: 73.23. Hk, 73.63.Kv, 71.70.Ej The spin of an electron in a quantum dot (QD) is one of the candidates for a scaleable quantum bit, the fundamental unit in quantum computation and quantum communication schemes [1]. Experimental realizations are on the one hand pursued using top-down approaches. This usually involves lateral gate electrodes electrostatically confining few or a single electron in a two dimensional electron gas close to the surface of a Ga(Al)As based heterostructure [2]. Such systems offer good tunability and controlled coupling of multiple spins has been demonstrated [3]. On the other hand, bottom up systems such as self assembled QDs [4] and carbon nanotubes [5] are expected to scale more easily. Semiconductor nanowires have emerged as a promising bottom-up fabricated system for electronic and optical device applications [6]. We have recently demonstrated the creation of few-electron QDs using InAs nanowire heterostructures [7] with two InP barriers. In the following we set out to investigate the spin properties of the first few orbital levels of these QDs.We utilize transport spectroscopy to measure the Zeeman splitting of the energy levels as a function of magnetic field and thereby determine the effective electron g-factor (g * ). The g-factor of bulk InAs, which crystalizes in the zinc-blende (ZB) structure, has been found to be g * = −14.7 [8]. However, InAs nanowires can exhibit both zinc-blende and wurtzite (WZ) type crystal structure[9] depending on diameter and growth conditions and so far very little is known about band parameters in WZ InAs. In low-dimensional semiconductor heterostructures the g factor depends critically on system size and dimensionality [10]. We show that varying the size of our nanowire dots allows us to tune g * from a value close to the InAs bulk value down to |g * | = 2.3±0.3. The possibility to have multiple dots along a nanowire, each with a different g-factor, makes such systems interesting candidates for realizations of individually addressable spin qubits.Using chemical beam epitaxy InAs nanowires containing QDs were grown catalytically from Au nanoparticles deposited on a <111>B InAs substrate [11,12]. The * Electronic address: andreas.fuhrer@ftf.lth.se nanowires typically grow perpendicular to the substrate and high resolution scanning transmission electron microscope (STEM) images indicate that most of them

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Observation of spin splitting in single InAs self-assembled quantum dots in AlAs

Cited by 57 publications

References 11 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

Fermi-edge singularities in transport through quantum dots

Tunable effectivegfactor in InAs nanowire quantum dots

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