Hole Spin Coherence in a Ge/Si Heterostructure Nanowire

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

doi:10.1021/nl501242b

Cited by 86 publications

(100 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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] .…”

mentioning

confidence: 94%

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

Zarassi

Danon

et al. 2017

Phys. Rev. B

View full text Add to dashboard Cite

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...

show abstract

mentioning

confidence: 94%

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

Zarassi

Danon

et al. 2017

Phys. Rev. B

View full text Add to dashboard Cite

show abstract

“…For Ge-Si core-shell nanowires, there have been reports on charge sensing [17] spin coherence [18], and spin relaxation [19]. The authors of the latter performed their experiments along a single magnetic field axis and concluded additional work was needed to pinpoint the spin relaxation mechanism.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic Pauli spin blockade in hole quantum dots

Brauns

Ridderbos

et al. 2016

Phys. Rev. B

View full text Add to dashboard Cite

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.

show abstract

“…While bare InAs and InSb NWs have been the workhorse systems [23][24][25][26][27], spin qubits may also be implemented in core/shell NWs such as Ge/Si [28][29][30][31], for which a large degree of external control has been predicted [32]. As electrons and holes interact with lattice vibrations, understanding of the quantum mechanical behavior of the system requires knowledge of the phonon bath.…”

Section: Introductionmentioning

confidence: 99%

Acoustic phonons and strain in core/shell nanowires

2014

View full text Add to dashboard Cite

We study theoretically the low-energy phonons and the static strain in cylindrical core/shell nanowires (NWs). Assuming pseudomorphic growth, isotropic media, and a force-free wire surface, we derive algebraic expressions for the dispersion relations, the displacement fields, and the stress and strain components from linear elasticity theory. Our results apply to NWs with arbitrary radii and arbitrary elastic constants for both core and shell. The expressions for the static strain are consistent with experiments, simulations, and previous analytical investigations; those for phonons are consistent with known results for homogeneous NWs. Among other things, we show that the dispersion relations of the torsional, longitudinal, and flexural modes change differently with the relative shell thickness, and we identify new terms in the corresponding strain tensors that are absent for uncapped NWs. We illustrate our results via the example of Ge/Si core/shell NWs and demonstrate that shell-induced strain has large effects on the hole spectrum of these systems.

show abstract

Hole Spin Coherence in a Ge/Si Heterostructure Nanowire

Cited by 86 publications

References 52 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

Anisotropic Pauli spin blockade in hole quantum dots

Acoustic phonons and strain in core/shell nanowires

Contact Info

Product

Resources

About