Resonant nuclear spin pumping in (In,Ga)As quantum dots

Cherbunin, R. V.; Flisinski, K.; Gerlovin, I. Ya.; Ignatiev, I. V.; Kuznetsova, Maria; Petrov, M. Yu.; Yakovlev, D. R.; Reuter, D.; Wieck, A. D.; Bayer, М.

doi:10.1103/physrevb.84.041304

Cited by 16 publications

(20 citation statements)

References 12 publications

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“…These features have enabled the observation of isotope-selective NMR of the nuclear spins associated with strain-free GaAs quantum dots 12,13 . Self-assembled quantum dots, attractive for single photon generation and opticallycontrolled spin qubits 2 , have highly inhomogeneous nuclear spins 5,[14][15][16] Here we use chirped NMR pulses. The main concept is that by sweeping over a large frequency range, the pulse addresses each nuclear spin at some point.…”

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confidence: 99%

Manipulation of the nuclear spin ensemble in a quantum dot with chirped magnetic resonance pulses

et al. 2014

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The nuclear spins in nano-structured semiconductors play a central role in quantum applications [1][2][3][4] . The nuclear spins represent a useful resource for generating local magnetic 5 fields but nuclear spin noise represents a major source of dephasing for spin qubits 2,3 . Controlling the nuclear spins enhances the resource while suppressing the noise. Nuclear magnetic resonance (NMR) techniques are challenging: the group-III and group-V isotopes have large spins with widely different gyromagnetic-ratios; in strained material there are large atom-dependent quadrupole-shifts 6 ;nano-scale NMR is hard to detect 7,8 . We report NMR on 100, 000 nuclear spins of a quantum dot using chirped radio-frequency pulses. Following polarization, we demonstrate a reversal of the nuclear spin. We can flip the nuclear spin back-and-forth a hundred times. We demonstrate that chirped-NMR is a powerful way of determining the chemical composition, the initial nuclear spin temperatures and quadrupole frequency distributions for all the main isotopes. The key observation is a plateau in the NMR signal as a function of sweep-rate: we achieve inversion at the first quantum transition for all isotopes simultaneously. These experiments represent a generic technique for manipulating nano-scale inhomogeneous nuclear spin ensembles and open the way to probe the coherence of such mesoscopic systems.NMR signals can be boosted by polarizing the nuclei. This is particularly beneficial on the nano-scale where NMR signals are invariably small and hard to detect. The nuclear spins in a self-assembled quantum dot can be polarized optically by exploiting the hyperfine interaction with an electron spin 3,5 . Extremely long-lived polarizations 4,9-11 up to about 50% have been achieved. The nuclear spin polarization results in a shift of the optical resonance, the Overhauser shift, facilitating its sensitive detection 5 . These features have enabled the observation of isotope-selective NMR of the nuclear spins associated with strain-free GaAs quantum dots 12,13 . Self-assembled quantum dots, attractive for single photon generation and opticallycontrolled spin qubits 2 , have highly inhomogeneous nuclear spins 5,[14][15][16] Here we use chirped NMR pulses. The main concept is that by sweeping over a large frequency range, the pulse addresses each nuclear spin at some point. For a spin-1 2 nucleus, a 2-level system, the Hamiltonian in the rotating frame is,where h is the Planck constant, I the nuclear spin, γ the gyromagnetic ratio of the nuclear isotope (in frequency units) and ∆ν(t) is the time-dependent detuning between the radio frequency (RF) excitation and the Larmor frequency ν L = γB z . The coupling between the RF magnetic field B x and the spin, the second term in the Hamiltonian, leads to an avoided crossing in the eigen-energies with splitting hν RF , Fig. 1a , where ν RF = γB x . On traversing the avoided crossing from large and negative ∆ν to large and positive ∆ν with a single pulse (N = 1) at sweep rate α, the probability that t...

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Manipulation of the nuclear spin ensemble in a quantum dot with chirped magnetic resonance pulses

et al. 2014

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“…This value is somewhat larger than the one obtained in another experiment with similar QDs. 11 A possible reason for this overestimation of the NSF amplitude is the increase ofthe wings of the Hanle curves due to polarization of quadrupole-split nuclear spin states, which becomes noticeable at magnetic fields |B x | ∼ 20 mT and larger. 20 By adding this polarization phenomenologically into the model, we were able to reduce the calculated NSF amplitude.…”

Section: Effect Of Nuclear Spin Fluctuationsmentioning

confidence: 99%

Hanle effect in (In,Ga)As quantum dots: Role of nuclear spin fluctuations

et al. 2013

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The role of nuclear spin fluctuations in the dynamic polarization of nuclear spins by electrons is investigated in (In,Ga)As quantum dots. The photoluminescence polarization under circularly polarized optical pumping in transverse magnetic fields (Hanle effect) is studied. A weak additional magnetic field parallel to the optical axis is used to control the efficiency of nuclear spin cooling and the sign of nuclear spin temperature. The shape of the Hanle curve is drastically modified with changing this control field, as observed earlier in bulk semiconductors and quantum wells. However, the standard nuclear spin cooling theory, operating with the mean nuclear magnetic field (Overhauser field), fails to describe the experimental Hanle curves in a certain range of control fields. This controversy is resolved by taking into account the nuclear spin fluctuations owed to the finite number of nuclei in the quantum dot. We propose a model describing cooling of the nuclear spin system by electron spins experiencing fast vector precession in the random Overhauser fields of nuclear spin fluctuations. The model allows us to accurately describe the measured Hanle curves and to determine the parameters of the electron-nuclear spin system of the studied quantum dots.

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“…This introduces a non-homogeneous nuclear quadrupole interaction, changing the usual nuclear-spin dynamics 43 but also modifying the NMR spectrum both in the single QDs 36 and in the QD ensembles. 44,45 The microscopic analysis of the quadrupole interaction is a rather complex problem while any direct experimental measurement of its magnitude would hardly be realized in practice. Since only scant experimental progress can be expected thereupon, an atomistic analysis would at least give some microscopic information within the framework of a chosen model.…”

Section: Introductionmentioning

confidence: 99%

“…Further calculations allow the inter- pretation of the NMR transitions that can be detected in the ensemble of such QDs. 35,44,45 The paper is organized as follows. In Sec.…”

Section: Introductionmentioning

confidence: 99%

Reconstruction of nuclear quadrupole interaction in (In,Ga)As/GaAs quantum dots observed by transmission electron microscopy

et al. 2016

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A microscopic study of the individual annealed (In,Ga)As/GaAs quantum dots is done by means of highresolution transmission electron microscopy. The Cauchy-Green strain-tensor component distribution and the chemical composition of the (In,Ga)As alloy are extracted from the microscopy images. The image processing allows for the reconstruction of the strain-induced electric-field gradients at the individual atomic columns extracting thereby the magnitude and asymmetry parameter of the nuclear quadrupole interaction. Nuclear magnetic resonance absorption spectra are analyzed for parallel and transverse mutual orientations of the electricfield gradient and a static magnetic field.

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Resonant nuclear spin pumping in (In,Ga)As quantum dots

Cited by 16 publications

References 12 publications

Manipulation of the nuclear spin ensemble in a quantum dot with chirped magnetic resonance pulses

Manipulation of the nuclear spin ensemble in a quantum dot with chirped magnetic resonance pulses

Hanle effect in (In,Ga)As quantum dots: Role of nuclear spin fluctuations

Reconstruction of nuclear quadrupole interaction in (In,Ga)As/GaAs quantum dots observed by transmission electron microscopy

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