Antilocalization of Coulomb Blockade in a Ge/Si Nanowire

Higginbotham, Andrew; Kuemmeth, Ferdinand; Larsen, T. W.; Fitzpatrick, Mattias; Yao, Jun; Yan, Hao; Lieber, Charles M.; Marcus, C. M.

doi:10.1103/physrevlett.112.216806

Cited by 60 publications

(80 citation statements)

References 44 publications

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“…Furthermore, the holes show high mobilities [38,42], long mean free paths [37], and Coulomb interaction strongly influences their properties [45]. Longitudinal confinement in these NWs results in tunable single and double QDs [40] with anisotropic and confinement-dependent g factors [46,47], in long relaxation [43] and coherence times [48] as well as in short SOI lengths [49]. Moreover, strongly anisotropic tunable g factors and long spin phonon relaxation times [50] were predicted as well as the usability for quantum information processing based on hole spin qubits [51].…”

Section: Introductionmentioning

confidence: 99%

Majorana fermions in Ge/Si hole nanowires

2014

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We consider Ge/Si core/shell nanowires with hole states coupled to an s-wave superconductor in the presence of electric and magnetic fields. We employ a microscopic model that takes into account material-specific details of the band structure such as strong and electrically tunable Rashba-type spin-orbit interaction and g factor anisotropy for the holes. In addition, the proximity-induced superconductivity Hamiltonian is derived starting from a microscopic model. In the topological phase, the nanowires host Majorana fermions with localization lengths that depend strongly on both the magnetic and electric fields. We identify the optimal regime in terms of the directions and magnitudes of the fields in which the Majorana fermions are the most localized at the nanowire ends. In short nanowires, the Majorana fermions hybridize and form a subgap fermion whose energy is split away from zero and oscillates as a function of the applied fields. The period of these oscillations could be used to measure the dependence of the spin-orbit interaction on the applied electric field and the g factor anisotropy.

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Section: Introductionmentioning

confidence: 99%

Majorana fermions in Ge/Si hole nanowires

2014

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“…Despite these profound theoretical contributions, only a few experiments in Ge-Si core-shell nanowires have been reported including Josephson junctions [22], spin-filling [23], spin relaxation [24], spin coherence [25], charge sensing [26] in the many-hole regime, and signatures of weak antilocalization [27].…”

Section: Introductionmentioning

confidence: 99%

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

Brauns

Ridderbos

et al. 2016

Phys. Rev. B

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We present angle-dependent measurements of the effective g factor g in a Ge-Si core-shell nanowire quantum dot. g is found to be maximum when the magnetic field is pointing perpendicularly to both the nanowire and the electric field induced by local gates. Alignment of the magnetic field with the electric field reduces g significantly. g is almost completely quenched when the magnetic field is aligned with the nanowire axis. These findings confirm recent calculations, where the obtained anisotropy is attributed to a Rashba-type spin-orbit interaction induced by heavy-hole light-hole mixing. In principle, this facilitates manipulation of spin-orbit qubits by means of a continuous high-frequency electric field.

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“…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][15][16][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] .…”

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confidence: 99%

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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Antilocalization of Coulomb Blockade in a Ge/Si Nanowire

Cited by 60 publications

References 44 publications

Majorana fermions in Ge/Si hole nanowires

Majorana fermions in Ge/Si hole nanowires

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

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

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