Electrical control of spin coherence in semiconductor nanostructures

Salis, G.; Kato, Yuichiro; Ensslin, Klaus; Driscoll, D. C.; Gossard, A. C.; Awschalom, D. D.

doi:10.1038/414619a

Cited by 307 publications

(249 citation statements)

References 19 publications

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“…Electrical control of isolated spins through their g-factors is highly desireable for implementation of quantum gate operations. To date, electrical control of g-factors has only been observed in ensembles of electrons in quantum wells by shifting the electron wavefunctions into different materials [10,11,12,13]. In this Letter we present a striking electric field resonance in the g-factor for molecular spin states confined to a single quantum dot molecule.…”

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confidence: 91%

Electrically TunablegFactors in Quantum Dot Molecular Spin States

et al. 2006

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We present a magneto-photoluminescence study of individual vertically stacked InAs/GaAs quantum dot pairs separated by thin tunnel barriers. As an applied electric field tunes the relative energies of the two dots, we observe a strong resonant increase or decrease in the g-factors of different spin states that have molecular wavefunctions distributed over both quantum dots. We propose a phenomenological model for the change in g-factor based on resonant changes in the amplitude of the wavefunction in the barrier due to the formation of bonding and antibonding orbitals. PACS numbers: 75.40.Gb, 78.20.Ls, 78.47.+p, 78.67.Hc Quantum Dots and Quantum Dot Molecules (QDMs) have proven to be a versatile medium for isolating and manipulating spins [1,2], which are of great interest for quantum information processing [3,4]. In particular, photoluminescence (PL) spectra have been used in self-assembled QDMs to observe coherent tunneling [5,6,7,8] and identify spin interactions through fine structure [9]. Electrical control of isolated spins through their g-factors is highly desireable for implementation of quantum gate operations. To date, electrical control of g-factors has only been observed in ensembles of electrons in quantum wells by shifting the electron wavefunctions into different materials [10,11,12,13]. In this Letter we present a striking electric field resonance in the g-factor for molecular spin states confined to a single quantum dot molecule.To our knowledge this is the first observation of electrical control over the g-factor for a single confined spin. Moreover, the isolation of a single QDM allows us to spectrally resolve and identify individual molecular spin states that have different g-factor behaviors. In Fig. 1a we indicate molecular spin states of both the neutral exciton (X 0 , one electron recombining with one hole) and positive trion (X + , electron-hole recombination in the presence of an extra hole) at zero magnetic field. The different electric field dependences of the g-factors for these states is apparent in Fig. 1b, where the splitting of PL lines increases for some molecular spin states and decreases for others. This electric field dependence is nearly an order of magnitude larger than previously reported in quantum wells [10,11,12,13]. The effect arises from the formation of bonding and antibonding orbitals, which results in a change in the amplitude of the wavefunction in the barrier at resonance.Our QDMs consist of two vertically stacked selfassembled InAs dots truncated at a thickness of 2.5 nm and separated by a 2 nm GaAs tunneling barrier [14]. As an applied electric field tunes the relative energies of the two dots, strong tunnel coupling between the hole states creates the molecular spin states. Unlike samples with a thicker tunnel barrier [5], the states retain molecular character throughout the observed range of electric fields. We present data from a single molecule, but the universality of the behavior has been verified by detailed studies of 7 other molecules from the same ...

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confidence: 91%

Electrically TunablegFactors in Quantum Dot Molecular Spin States

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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].…”

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“…It was further shown that changing the dot length L allows us to design QDs along a nanowire with different specific spin splittings in a constant magnetic field. Future development of graded heterostructures is expected to allow individual gate tunable spin splittings [13,19] in a series of dots along a nanowire, which makes nanowire QDs containing a single electron spin interesting systems for the realization of qubits.…”

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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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“…In the presence of an electric field the minimum of the confining potential may be displaced with the center of the well, whereas the implicitly of the envelope of the wave function is conserved. This particular property of the partially filled triangular well makes it suitable for the practical realization of the electronic devices based on the manipulation of the g-factor for spintronic application [8].…”

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confidence: 99%

Magnetotransport in Al xGa x-1As quantum wells with different potential shapes

Mamani¹,

Duarte²,

Gusev³

et al. 2006

Braz. J. Phys.

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We compare the transport properties for triangular, parabolic and cubic quantum wells. We calculate the transport mobility for electrons belonging to the different subbands. We obtain the energy spacing between first and second subbands from the electron sheet density and compare results for different potential profiles. We find that experimental results are in quantitative agreements with our calculations.

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Electrical control of spin coherence in semiconductor nanostructures

Cited by 307 publications

References 19 publications

Electrically TunablegFactors in Quantum Dot Molecular Spin States

Electrically TunablegFactors in Quantum Dot Molecular Spin States

Tunable effectivegfactor in InAs nanowire quantum dots

Magnetotransport in Al xGa x-1As quantum wells with different potential shapes

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