Heavy-Hole States in Germanium Hut Wires

Watzinger, Hannes; Kloeffel, Christoph; Vukušić, Lada; Rossell, Marta D.; Sessi, Violetta; Kukučka, Josip; Kirchschlager, R.; Lausecker, E.; Truhlar, Alisha; Gläser, Martin; Rastelli, Armando; Fuhrer, Andreas; Loss, Daniel; Katsaros, Georgios

doi:10.1021/acs.nanolett.6b02715

Cited by 86 publications

(101 citation statements)

References 42 publications

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“…e) d 2 I/ d V 2 versus V SD and angle of magnetic field for B = 1 T and V G = 320.9 mV. A g ‐factor anisotropy of about 8, underlying the heavy‐hole character of the confined states, [ 44 ] is measured. Zero degrees correspond to the parallel magnetic field direction B || and 90° to the out‐of‐plane field B ⊥ .…”

Section: Figurementioning

confidence: 99%

Site‐Controlled Uniform Ge/Si Hut Wires with Electrically Tunable Spin–Orbit Coupling

et al. 2020

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attention due to its high hole mobility, [10][11][12][13] low effective mass in 2D hole gases, [14,15] good contacts with metals, [16][17][18] strong spin-orbit interactions, [19][20][21][22] capability of isotopic purification, [23] and compatibility with Si. These attractive features make Ge a promising candidate not only as a transistor channel material but also as a host for spin [6,24,25] and even topological qubits. [26,27] Excitingly, the first hole spin qubit [6] and proximity-induced superconductivity with a hard gap [28] have been realized recently in 1D Ge.Despite much progress that has been made so far, it remains a formidable challenge to have individuals as well as arrays of NWs with a high degree of addressability and scalability for the next generation of NW-based quantum devices. For example, in the field of group III-V semiconductors, precisely positioned NW networks have been achieved with predefined metal islands. [29] The out-of-plane grown NW structures, however, need to be transferred from the growth wafer to a second substrate for device fabrication, which limits their scalability. [7,29] Very recently, high-quality inplane NW networks have been successfully demonstrated with Semiconductor nanowires have been playing a crucial role in the development of nanoscale devices for the realization of spin qubits, Majorana fermions, single photon emitters, nanoprocessors, etc. The monolithic growth of site-controlled nanowires is a prerequisite toward the next generation of devices that will require addressability and scalability. Here, combining top-down nanofabrication and bottom-up self-assembly, the growth of Ge wires on prepatterned Si (001) substrates with controllable position, distance, length, and structure is reported. This is achieved by a novel growth process that uses a SiGe strain-relaxation template and can be potentially generalized to other material combinations. Transport measurements show an electrically tunable spin-orbit coupling, with a spin-orbit length similar to that of III-V materials. Also, charge sensing between quantum dots in closely spaced wires is observed, which underlines their potential for the realization of advanced quantum devices. The reported results open a path toward scalable qubit devices using nanowires on silicon.

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Section: Figurementioning

confidence: 99%

Site‐Controlled Uniform Ge/Si Hut Wires with Electrically Tunable Spin–Orbit Coupling

et al. 2020

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“…The hole states are predominantly heavy hole in character. However, even a small admixture of light-hole states reduces the g-factor from the heavy hole limit by a large amount 67,68 . This light-hole admixture is size-dependent which can explain the dependence of the g-factor on A VC .…”

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Correlations between optical properties and Voronoi-cell area of quantum dots

et al. 2019

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A semiconductor quantum dot (QD) can generate highly indistinguishable single-photons at a high rate. For application in quantum communication and integration in hybrid systems, control of the QD optical properties is essential. Understanding the connection between the optical properties of a QD and the growth process is therefore important. Here, we show for GaAs QDs, grown by infilling droplet-etched nano-holes, that the emission wavelength, the neutral-to-charged exciton splitting, and the diamagnetic shift are strongly correlated with the capture zone-area, an important concept from nucleation theory. We show that the capture-zone model applies to the growth of this system even in the limit of a low QD-density in which atoms diffuse over µm-distances. The strong correlations between the various QD parameters facilitate preselection of QDs for applications with specific requirements on the QD properties; they also suggest that a spectrally narrowed QD distribution will result if QD growth on a regular lattice can be achieved. arXiv:1902.10145v3 [cond-mat.mes-hall]

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“…The new two-qubit coupling mechanism and enhanced spin lifetimes predicted here greatly improve the prospects for a practical implementation of quantum information using extensively studied hole spin systems. [35][36][37][38][39][40][41][42][43][44] For hole spins bound to acceptor atoms many milestones have already been achieved experimentally, from the placement of acceptors near an interface 45 , to the measurement of single-acceptor states 46 , and coupling between two acceptors. 47,48 The results reported here also highlight the advantages of acceptors versus quantum dots as a suitable platform for hole spin qubits.…”

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Entanglement control and magic angles for acceptor qubits in Si

Abadillo-Uriel

Salfi

et al. 2018

Applied Physics Letters

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Full electrical control of quantum bits could enable fast, low-power, scalable quantum computation. Although electric dipoles are highly attractive to couple spin qubits electrically over long distances, mechanisms identified to control two-qubit couplings do not permit single-qubit operations while two-qubit couplings are off. Here we identify a mechanism to modulate electrical coupling of spin qubits that overcomes this drawback for hole spin qubits in acceptors,that is based on the electrical tuning of the direction of the spin-dependent electric dipole by a gate. In this way, inter-qubit coupling can be turned off electrically by tuning to a "magic angle" of vanishing electric dipole-dipole interactions, while retaining the ability to manipulate the individual qubits. This effect stems from the interplay of the T d symmetry of the acceptor state in the Si lattice with the magnetic field orientation, and the spin-3/2 characteristic of hole systems. Magnetic field direction also allows to greatly suppress spin relaxation by phonons that limit single qubit performance, while retaining sweet spots where the qubits are insensitive to charge noise. Our findings can be directly applied to state-of-the-art acceptor based architectures, for which we propose suitable protocols to practically achieve full electrical tunability of entanglement and the realization of a decoherence-free subspace.

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Heavy-Hole States in Germanium Hut Wires

Cited by 86 publications

References 42 publications

Site‐Controlled Uniform Ge/Si Hut Wires with Electrically Tunable Spin–Orbit Coupling

Site‐Controlled Uniform Ge/Si Hut Wires with Electrically Tunable Spin–Orbit Coupling

Correlations between optical properties and Voronoi-cell area of quantum dots

Entanglement control and magic angles for acceptor qubits in Si

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