Electrostatic Detection of Shubnikov–de Haas Oscillations in Bilayer Graphene by Coulomb Resonances in Gate‐Defined Quantum Dots

Banszerus, Luca; Fabian, Thomas; Möller, S.; Icking, Eike; Heiming, Henning; Trellenkamp, Stefan; Lentz, Florian; Otto, Martin; Watanabe, Kenji; Taniguchi, Takashi; Libisch, Florian; Volk, C.; Stampfer, Christoph

doi:10.1002/pssb.202000333

Cited by 12 publications

(9 citation statements)

References 29 publications

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“…time in BLG QDs 13 . We therefore apply a finite magnetic field of B ⊥ = 2.4 T to lift the spin and valley degeneracy and, furthermore, to reduce the tunneling rates to the reservoirs 13 , 26 , by altering the density of states in the reservoirs 35 and widening the tunneling barriers. Figure 2 a shows the applied square pulse scheme with amplitude V A and pulse widths τ i and τ m .…”

Section: Resultsmentioning

confidence: 99%

Spin relaxation in a single-electron graphene quantum dot

et al. 2022

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The relaxation time of a single-electron spin is an important parameter for solid-state spin qubits, as it directly limits the lifetime of the encoded information. Thanks to the low spin-orbit interaction and low hyperfine coupling, graphene and bilayer graphene (BLG) have long been considered promising platforms for spin qubits. Only recently, it has become possible to control single-electrons in BLG quantum dots (QDs) and to understand their spin-valley texture, while the relaxation dynamics have remained mostly unexplored. Here, we report spin relaxation times (T1) of single-electron states in BLG QDs. Using pulsed-gate spectroscopy, we extract relaxation times exceeding 200 μs at a magnetic field of 1.9 T. The T1 values show a strong dependence on the spin splitting, promising even longer T1 at lower magnetic fields, where our measurements are limited by the signal-to-noise ratio. The relaxation times are more than two orders of magnitude larger than those previously reported for carbon-based QDs, suggesting that graphene is a potentially promising host material for scalable spin qubits.

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Section: Resultsmentioning

confidence: 99%

Spin relaxation in a single-electron graphene quantum dot

et al. 2022

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“…In Fig. 2 tions in the lever-arm, which are due to Shubnikov-de-Haas oscillations in the lead region [24]. With increasing V G , first the GS transition enters the bias window, then additional transitions follow, each appearing as feature of increased differential transconductance, giving rise to a rich spectrum.…”

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confidence: 96%

“…v )µ B B ⊥ , with the spin g-factor g s = 2, the single-particle (wavefunction dependent) valley g-factor g (1) v and the Bohr magneton µ B [16,[22][23][24]. Note that the valley g-factor is usually around one order of magnitude larger than the spin g-factor.…”

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confidence: 99%

Probing two-electron multiplets in bilayer graphene quantum dots

Möller,

Banszerus,

Knothe

et al. 2021

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We report on finite bias spectroscopy measurements of the two-electron spectrum in a gate defined bilayer graphene (BLG) quantum dot for varying magnetic fields. The spin and valley degree of freedom in BLG give rise to multiplets of 6 orbital symmetric and 10 orbital anti-symmetric states. We find that orbital symmetric states are lower in energy and separated by ≈ 0.4 − 0.8 meV from orbital anti-symmetric states. The symmetric multiplet exhibits an additional energy splitting of its 6 states of ≈ 0.15 − 0.5 meV due to lattice scale interactions. The experimental observations are supported by theoretical calculations, which allow to determine that inter-valley scattering and 'current-current' interaction constants are of the same magnitude in BLG.

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“…In order to study the spin dynamics of a single-electron in the BLG QD, we now focus on the first charge tran-sition (N = 0 to 1) and apply a perpendicular magnetic field, B ⊥ , to lift the spin and valley degeneracy of the QD and, crucially, to reduce the tunneling rates between the QD and the source-drain reservoirs [14,15,36]. At B ⊥ = 1.5 T, a tunneling current of I ≈ 720 fA at V A = 0 V is observed, corresponding to a combined tunneling rate through the QD of Γ = I/e = Γ L Γ R /(Γ L + Γ R ) ≈ 4.5 MHz.…”

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confidence: 99%

Pulsed-gate spectroscopy of single-electron spin states in bilayer graphene quantum dots

Banszerus,

Hecker,

Icking

et al. 2020

Preprint

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Graphene and bilayer graphene quantum dots are promising hosts for spin qubits with long coherence times. Although recent technological improvements make it possible to confine single electrons electrostatically in bilayer graphene quantum dots, and their spin and valley texture of the single particle spectrum has been studied in detail, their relaxation dynamics remains still unexplored. Here, we report on transport through a high-frequency gate controlled single-electron bilayer graphene quantum dot. By transient current spectroscopy of single-electron spin states, we extract a lower bound of the spin relaxation time of 0.5 µs. This result represents an important step towards the investigation of spin coherence times in graphene-based quantum dots and the implementation of spin-qubits.

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Electrostatic Detection of Shubnikov–de Haas Oscillations in Bilayer Graphene by Coulomb Resonances in Gate‐Defined Quantum Dots

Cited by 12 publications

References 29 publications

Spin relaxation in a single-electron graphene quantum dot

Spin relaxation in a single-electron graphene quantum dot

Probing two-electron multiplets in bilayer graphene quantum dots

Pulsed-gate spectroscopy of single-electron spin states in bilayer graphene quantum dots

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