Measurement of valley splitting in high-symmetry Si/SiGe quantum dots

Borselli, Matthew; Ross, Richard S.; Kiselev, A. A.; Croke, E. T.; Holabird, K.S.; Deelman, Peter W.; Warren, Leslie D.; Alvarado-Rodriguez, Ivan; Milosavljevic, I.; Ku, Fiona; Wong, William S.; Schmitz, A.; Sokolich, M.; Gyure, Mark F.; Hunter, A. T.

doi:10.1063/1.3569717

Cited by 103 publications

(108 citation statements)

References 14 publications

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“…This remaining degeneracy is further split if the perpendicular confinement is asymmetric, resulting in an energy difference called the ground-state gap. [42][43][44][45][46][47][48][49] As the valley degeneracy is believed to be the main obstacle for silicon-based quantum computation, 46,50,51 a large valley splitting is desired. If this is the case, the multivalley system can be reduced to an effective single-valley qubit, a potentially nuclear-spin-free analog to the well-known GaAs counterpart.…”

Section: Introductionmentioning

confidence: 99%

Theory of spin relaxation in two-electron laterally coupled Si/SiGe quantum dots

2012

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Highly accurate numerical results of phonon-induced two-electron spin relaxation in silicon double quantum dots are presented. The relaxation, enabled by spin-orbit coupling and the nuclei of 29 Si (natural or purified abundance), is investigated for experimentally relevant parameters, the interdot coupling, the magnetic field magnitude and orientation, and the detuning. We calculate relaxation rates for zero and finite temperatures (100 mK), concluding that our findings for zero temperature remain qualitatively valid also for 100 mK. We confirm the same anisotropic switch of the axis of prolonged spin lifetime with varying detuning as recently predicted in GaAs. Conditions for possibly hyperfine-dominated relaxation are much more stringent in Si than in GaAs. For experimentally relevant regimes, the spin-orbit coupling, although weak, is the dominant contribution, yielding anisotropic relaxation rates of at least two orders of magnitude lower than in GaAs.

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Section: Introductionmentioning

confidence: 99%

Theory of spin relaxation in two-electron laterally coupled Si/SiGe quantum dots

2012

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“…The multiplicity of the Hilbert space brought about by the existence of equivalent valleys has been shown to hamper spin QC. [71][72][73][74][75] At the same time, the interface potential gives rise to a valley-orbit coupling, which has been studied extensively in recent years, both experimentally [76][77][78][79][80][81] and theoretically. [82][83][84][85][86][87][88][89][90] Addressing specific valley eigenstates is a profound, challenging and unresolved problem.…”

Section: Introductionmentioning

confidence: 99%

Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling

Culcer

2012

Phys. Rev. B

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A gate electric field has a small but non-negligible effect on the phase of the valley-orbit coupling in Si quantum dots. Finite interdot tunneling between valley eigenstates in a double quantum dot is enabled by a small difference in the phase of the valley-orbit coupling between the two dots, and it in turn allows controllable rotations of two-dot valley eigenstates at a level anticrossing. We present a comprehensive analytical discussion of this process, with estimates for realistic structures.

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“…Figure 3d shows data for the 0-to-1 transition; in this panel, a series of 420 ns square pulses with amplitude V P was applied to gate R with a repetition rate of 1 MHz. The singleelectron excited state with the lowest energy is 56 µeV above the ground state, an energy that is consistent with a predominately valley-like excitation in Si/SiGe quantum devices [23,30,41,42]. In the upper left corner of Figure 3d a line extends towards the lower left and intersects with the so-called "loading line."…”

Section: Resultsmentioning

confidence: 86%

“…Figure 2a shows a schematic cross section of the Si/SiGe nanomembrane-based double quantum dot studied here, in which all carriers are induced by gates and no dopants are placed in the active area of the device [30][31][32][33], eliminating a key source of charge noise [34]. After the second heterostructure growth on the elastically relaxed SiGe nanomembrane, a 10 nm layer of Al 2 O 3 was grown by atomic layer deposition (ALD).…”

Section: Methodsmentioning

confidence: 99%

Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane

Knapp

Mohr

et al. 2016

Nanotechnology

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Abstract. We report the fabrication and characterization of a gate-defined double quantum dot formed in a Si/SiGe nanomembrane. In the past, all gatedefined quantum dots in Si/SiGe heterostructures were formed on top of straingraded virtual substrates. The strain grading process necessarily introduces misfit dislocations into a heterostructure, and these defects introduce lateral strain inhomogeneities, mosaic tilt, and threading dislocations. The use of a SiGe nanomembrane as the virtual substrate enables the strain relaxation to be entirely elastic, eliminating the need for misfit dislocations. However, in this approach the formation of the heterostructure is more complicated, involving two separate epitaxial growth procedures separated by a wet-transfer process that results in a buried non-epitaxial interface 625 nm from the quantum dot. We demonstrate that in spite of this buried interface in close proximity to the device, a double quantum dot can be formed that is controllable enough to enable tuning of the inter-dot tunnel coupling, the identification of spin states, and the measurement of a singlet-to-triplet transition as a function of an applied magnetic field.

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Measurement of valley splitting in high-symmetry Si/SiGe quantum dots

Cited by 103 publications

References 14 publications

Theory of spin relaxation in two-electron laterally coupled Si/SiGe quantum dots

Theory of spin relaxation in two-electron laterally coupled Si/SiGe quantum dots

Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling

Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane

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