Linear scaling between momentum and spin scattering in graphene

Józsa, C.; Maassen, T.; Popinciuc, M.; Zomer, P. J.; Veligura, A.; Jonkman, Harry T.; Wees, van Bart

doi:10.1103/physrevb.80.241403

Cited by 132 publications

(225 citation statements)

References 26 publications

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“…While most early graphene spin experiments showed spin lifetimes that are constant in gate voltage 12 , other work shows that spin lifetimes are affected by changes in carrier density 32 . Studies that observe gate voltage dependence have in common high contact resistance in the oxide tunnel barrier contacts, indicative of pinhole-free tunnel barriers that prevent back diffusion into the FM contact and subsequent fast spin relaxation 33 .…”

Section: Discussionmentioning

confidence: 99%

Homoepitaxial tunnel barriers with functionalized graphene-on-graphene for charge and spin transport

Friedman

Erve

et al. 2014

Nat Commun

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The coupled imperatives for reduced heat dissipation and power consumption in high-density electronics have rekindled interest in devices based on tunnelling. Such devices require mating dissimilar materials, raising issues of heteroepitaxy, layer uniformity, interface stability and electronic states that severely complicate fabrication and compromise performance. Twodimensional materials such as graphene obviate these issues and offer a new paradigm for tunnel barriers. Here we demonstrate a homoepitaxial tunnel barrier structure in which graphene serves as both the tunnel barrier and the high-mobility transport channel. We fluorinate the top layer of a graphene bilayer to decouple it from the bottom layer, so that it serves as a single-monolayer tunnel barrier for both charge and spin injection into the lower graphene channel. We demonstrate high spin injection efficiency with a tunnelling spin polarization 460%, lateral transport of spin currents in non-local spin-valve structures and determine spin lifetimes with the Hanle effect.

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Section: Discussionmentioning

confidence: 99%

Homoepitaxial tunnel barriers with functionalized graphene-on-graphene for charge and spin transport

Friedman

Erve

et al. 2014

Nat Commun

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“…For some precession curves there are a few sets of parameters that describe reasonably the experiment. In that case we fixed the spin-diffusion constant to the charge-diffusion constant, 39 leaving the spinrelaxation time as the only relevant fitting parameter. Generally, the spin valve signals at the Dirac point were too small to produce a useful precession curve.…”

Section: G Spin Precession In Graphene Ribbonsmentioning

confidence: 99%

Electronic spin transport in graphene field-effect transistors

et al. 2009

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Electronic spin transport in graphene field-effect transistors Popinciuc, M.; Jozsa, C.; Zomer, P. J.; Tombros, N.; Veligura, A.; Jonkman, H. T.; van Wees, B. J. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Spin transport experiments in graphene, a single layer of carbon atoms ordered in a honeycomb lattice, indicate spin-relaxation times that are significantly shorter than the theoretical predictions. We investigate experimentally whether these short spin-relaxation times are due to extrinsic factors, such as spin relaxation caused by low impedance contacts, enhanced spin-flip processes at the device edges, or the presence of an aluminum oxide layer on top of graphene in some samples. Lateral spin valve devices using a field-effect transistor geometry allowed for the investigation of the spin relaxation as a function of the charge density, going continuously from metallic hole to electron conduction ͑charge densities of n ϳ 10 12 cm −2 ͒ via the Dirac charge neutrality point ͑n ϳ 0͒. The results are quantitatively described by a one-dimensional spin-diffusion model where the spin relaxation via the contacts is taken into account. Spin valve experiments for various injector-detector separations and spin precession experiments reveal that the longitudinal ͑T 1 ͒ and the transversal ͑T 2 ͒ relaxation times are similar. The anisotropy of the spin-relaxation times ʈ and Ќ , when the spins are injected parallel or perpendicular to the graphene plane, indicates that the effective spin-orbit fields do not lie exclusively in the two-dimensional graphene plane. Furthermore, the proportionality between the spinrelaxation time and the momentum-relaxation time indicates that the spin-relaxation mechanism is of the Elliott-Yafet type. For carrier mobilities of 2 ϫ 10 3 -5ϫ 10 3 cm 2 / V s and for graphene flakes of 0.1-2 m in width, we found spin-relaxation times on the order of 50-200 ps, times which appear not to be determined by the extrinsic factors mentioned above.

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“…17,23 Early experiments on spin transport in exfoliated graphene were able to take advantage of the tunable carrier concentration (n) and observe a linear relationship between τ s and τ p , thus suggesting EY. 15,22 However, recent theoretical studies have shown that DP is expected to dominate over EY 21,24 and that Elliot's approach applied to graphene 17 predicts τ s = ( F ) 2 τ p /(∆ SO ) 2 , for which both Fermi energy F and τ p depend on carrier concentration, thus highlighting the need for experiments that can tune τ p at fixed n. * roland.kawakami@ucr.edu…”

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“…15,22 While Mg adsorbates modify τ p by introducing CI scattering and possibly local Rashba SO coupling, there are many alternative sources which might contribute to EY (i.e. weak scatterers, resonant scattering, phonon scattering) which could still present themselves as the carrier concentration is tuned leading to τ s ∼ D. Thus, EY spin relaxation originating from sources other than CI scattering is still viable.…”

mentioning

confidence: 99%

“…In graphene, two possible spin relaxation mechanisms are discussed in the literature: [14][15][16][17][18][19][20][21][22][23][24] the Elliot-Yafet (EY) mechanism, for which the spin relaxation time (τ s ) is proportional to the momentum scattering time (τ p ), and the D'yakonov-Perel (DP) mechanism, for which τ s ∝ 1/τ p . Complicating the situation are the many possible sources of spin relaxation in experiments on SiO 2 substrate including charged impurity (CI) scatterers, 16,17 Rashba SO coupling due toadatoms, 18,19,25 ripples, 20,21 and edge effects.…”

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confidence: 99%

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Effect ofin situdeposition of Mg adatoms on spin relaxation in graphene

et al. 2013

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We have systematically introduced charged impurity scatterers in the form of Mg adsorbates to exfoliated single layer graphene and observe little variation of the spin relaxation times despite pronounced changes in the charge transport behavior. All measurements are performed on non-local graphene tunneling spin valves exposed in-situ to Mg adatoms, thus systematically introducing atomic-scale charged impurity scattering. While charge transport properties exhibit decreased mobility and decreased momentum scattering times, the observed spin lifetimes are not significantly affected indicating that charged impurity scattering is inconsequential in the present regime of spin relaxation times (∼1 ns).

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Linear scaling between momentum and spin scattering in graphene

Abstract: Linear scaling between momentum and spin scattering in graphene Jozsa, C.; Maassen, T.; Popinciuc, M.; Zomer, P. J.; Veligura, A.; Jonkman, H. T.; van Wees, B. J.

Cited by 132 publications

References 26 publications

Homoepitaxial tunnel barriers with functionalized graphene-on-graphene for charge and spin transport

Homoepitaxial tunnel barriers with functionalized graphene-on-graphene for charge and spin transport

Electronic spin transport in graphene field-effect transistors

Effect ofin situdeposition of Mg adatoms on spin relaxation in graphene

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