Electric-field dependent<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>g</mml:mi></mml:math>-factor anisotropy in Ge-Si core-shell nanowire quantum dots

Brauns, Matthias; Ridderbos, Joost; Li, Ang; Bakkers, Erik P. A. M.; Zwanenburg, Floris A.

doi:10.1103/physrevb.93.121408

Cited by 64 publications

(75 citation statements)

References 48 publications

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“…We expand and adapt a previously developed rate equation model to analyze the magnetic-field evolution of the leakage current 24 . We also observe large and anisotropic g-factors in these dots, which supports recent theoretical predictions 25 and experimental observations 26,27 .The devices are fabricated on n-doped Si substrates covered with 500 nm of thermal SiO 2 and patterned with local gate arrays of Ti/Au stripes with center to center distance of 60 nm. The gates are covered by a 10 nm layer of HfO 2 dielectric.…”

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confidence: 58%

Magnetic field evolution of spin blockade in Ge/Si nanowire double quantum dots

Zarassi

Danon

et al. 2017

Phys. Rev. B

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We perform transport measurements on double quantum dots defined in Ge/Si core/shell nanowires and focus on Pauli spin blockade in the regime where tens of holes occupy each dot. We identify spin blockade through the magnetic field dependence of leakage current. We find both a dip and a peak in the leakage current at zero field. We analyze this behavior in terms of the quantum dot parameters such as coupling to the leads, interdot tunnel coupling as well as spin-orbit interaction. We find a lower bound for spin-orbit interaction with lso = 500 nm. We also extract large and anisotropic effective Landé g-factors, with larger g-factors in the direction perpendicular to the nanowire axis in agreement with previous studies and experiments but with larger values reported here.Studies of spin blockade in quantum dots are largely motivated by the proposals to build a spin-based quantum computer 1 , as spin blockade can be used for qubit initialization and readout 2,3 . At the same time, spin blockade and its lifting mechanisms offer a direct insight into spin relaxation and dephasing processes in semiconductors and provide deeper understanding of interactions between spin localized in a quantum dot and its environment, be it the lattice and its vibrations or nuclear spins, spin-orbit interaction, or coupling to spins in nearby dots or in the lead reservoirs 4-8 .Holes in Ge/Si nanowires offer a relatively unexplored platform for such studies 9 . On the one hand, hyperfine interaction is expected to be greatly reduced owing to the low abundance of nonzero nuclear spin isotopes in the group IV materials 10 . Moreover, holes weakly couple to nuclear spins due to their p-wave Bloch wave symmetry, thus they are expected to come with longer spin relaxation times 11 . Heavy/light hole degeneracy may also influence the spin blockade regime 12 . On the other hand, spin-orbit interaction is predicted 13 and suggested by experiments 14-17 to be strong in Ge/Si core/shell nanowires. This offers a path to electrical spin manipulation 18,19 , as well as to realizing Majorana fermions [20][21][22][23] .In this work we perform transport measurements on electrostatically defined double quantum dots 2 made in Ge/Si core/shell nanowires, and detect Pauli spin blockade at several charge degeneracy points. We expand and adapt a previously developed rate equation model to analyze the magnetic-field evolution of the leakage current 24 . We also observe large and anisotropic g-factors in these dots, which supports recent theoretical predictions 25 and experimental observations 26,27 .The devices are fabricated on n-doped Si substrates covered with 500 nm of thermal SiO 2 and patterned with local gate arrays of Ti/Au stripes with center to center distance of 60 nm. The gates are covered by a 10 nm layer of HfO 2 dielectric. Using a micromanipulator 28 the nanowires with a typical length of 4 µm and diameter of 30 nm are placed on top of these gates as shown in the inset of Fig. 1. After wet etching with buffered hydrofluoric acid, we sputter 15...

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confidence: 58%

Magnetic field evolution of spin blockade in Ge/Si nanowire double quantum dots

Zarassi

Danon

et al. 2017

Phys. Rev. B

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“…[26][27][28][29] Such experiments are relevant, because the applied bias between the two reservoirs serves as an energy scale, which, e.g., allows for the determination of the singlettriplet splitting 31 and the Zeeman splitting. 30 In summary, we demonstrate a high degree of control over the charge distribution in a double quantum dot. We have changed the mutual capacitances, a measure for the degree of separation of the dots, by a factor of six while keeping the capacitances between the left (right) dot and g3 (g5) almost constant.…”

Section: Figs 2(b)-2(e) Display Bias Spectroscopies Of Quantum Dots mentioning

confidence: 73%

Highly tuneable hole quantum dots in Ge-Si core-shell nanowires

Brauns

Ridderbos

et al. 2016

Applied Physics Letters

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We define single quantum dots of lengths varying from 60 nanometers up to nearly half a micron in Ge-Si core-shell nanowires. The charging energies scale inversely with the quantum dot length between 18 and 4 meV. Subsequently we split up a long dot into a double quantum dot with separate control over the tunnel couplings and the electrochemical potential of each dot. Both single and double quantum dot configurations prove to be very stable and show excellent control over the electrostatic environment of the dots, making this system a highly versatile platform for spin-based quantum computing.

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“…(1) we obtain g * y = 1.2 ± 0.2 at = 150 µeV. The g factor along this magnetic field direction is significantly lower than in single quantum dot measurements [15], where g * y = 2.7 ± 0.1 was maximal.…”

Section: Magnetospectroscopy Along Bymentioning

confidence: 93%

“…The onedimensional character of Ge-Si core-shell nanowires leads to unique electronic properties in the valence band, where heavy and light hole states are mixed [11][12][13]. The band mixing gives rise to an enhanced Rashba-type spin-orbit interaction (SOI) [13], leading to strongly anisotropic and electric-field dependent g factors [14,15]. This makes quantum dots in Ge-Si core-shell nanowires promising candidates for robust spin-orbit qubits.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic Pauli spin blockade in hole quantum dots

Brauns

Ridderbos

et al. 2016

Phys. Rev. B

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We present measurements on gate-defined double quantum dots in Ge-Si core-shell nanowires, which we tune to a regime with visible shell filling in both dots. We observe a Pauli spin blockade and can assign the measured leakage current at low magnetic fields to spin-flip cotunneling, for which we measure a strong anisotropy related to an anisotropic g factor. At higher magnetic fields we see signatures for leakage current caused by spin-orbit coupling between (1,1)-singlet and (2,0)-triplet states. Taking into account these anisotropic spin-flip mechanisms, we can choose the magnetic field direction with the longest spin lifetime for improved spin-orbit qubits.

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Electric-field dependentg-factor anisotropy in Ge-Si core-shell nanowire quantum dots

Cited by 64 publications

References 48 publications

Magnetic field evolution of spin blockade in Ge/Si nanowire double quantum dots

Magnetic field evolution of spin blockade in Ge/Si nanowire double quantum dots

Highly tuneable hole quantum dots in Ge-Si core-shell nanowires

Anisotropic Pauli spin blockade in hole quantum dots

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