Effect of the Zero-Mode Landau Level on Interlayer Magnetoresistance in Multilayer Massless Dirac Fermion Systems

Tajima, Naoya; Sugawara, Shinji; Kato, Reìzo; Nishio, Y.; Kajita, Kôji

doi:10.1103/physrevlett.102.176403

Cited by 140 publications

(150 citation statements)

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“…Landau level mixing plays a dominant role 35,36 . This model also does not hold at high magnetic fields (> ~ 3kG) where additional level splitting (due to effects such as spinorbit interactions) may become important.…”

Section: However We Note That This Model Is Not Valid In the Low Fielmentioning

confidence: 99%

“…Thus we conclude that the large negative CPP-MR originates from the graphene layers that are free of crystal defects (Raman D band is absent) and that are characterized by distortion-free 2D Raman band. The thinner 7 specimens (Figures 3c, d) show a distortion-free Raman 2D band, but it is accompanied by a Raman D band and no large negative CPP-MR has been observed in this case.Negative MR in the vicinity of zero magnetic field can originate from three sources: (a) weak localization 12 , (b) spin filtering and associated giant magnetoresistance (GMR) effect 2 and (c) interlayer tunneling between zero mode Landau levels [34][35][36][37] . Negative MR originating from weak localization gradually diminishes with increasing temperature due to reduction of phase coherence time at higher temperatures 12 .…”

mentioning

confidence: 99%

“…Thus, unlike ferromagnetic contacts, this electrode is not able to differentiate between various spin orientations. Thus we believe that the observed large MR in Figure 2 is not due to this spin filtering effect.Negative MR can also arise from an interlayer tunneling mechanism, which is often dubbed "interlayer magnetoresistance" or ILMR [34][35][36][37] . This effect is observed in a stack of two-dimensional (2D) massless Dirac electron systems.…”

mentioning

confidence: 99%

“…Thus with increasing magnetic field, degeneracy of the zero mode Landau level will increase, giving rise to larger interlayer tunneling current. This is the origin of large negative MR and is dubbed ILMR [34][35][36][37] .If the magnetic field is in-plane, it exerts Lorentz force on the electrons traveling out-ofplane and bends their trajectories. As a result, with increasing in-plane magnetic field effective interlayer tunneling distance increases, resulting in weaker tunneling probability and hence smaller interlayer tunneling current.…”

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confidence: 99%

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Giant Current-Perpendicular-to-Plane Magnetoresistance in Multilayer Graphene as Grown on Nickel

2014

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Strong magnetoresistance effects are often observed in ferromagnet-nonmagnet multilayers, which are exploited in state-of-the-art magnetic field sensing and data storage technologies. In this work we report a novel current-perpendicular-to-plane magnetoresistance effect in multilayer graphene as-grown on catalytic nickel surface by chemical vapor deposition. A negative magnetoresistance effect of ~10 4 % has been observed, which persists even at room temperature. This effect is correlated with the shape of the 2D peak as well as with the occurrence of D peak in the Raman spectrum of the as-grown multilayer graphene. The observed magnetoresistance is extremely high as compared to other known materials systems for similar temperature and field range, and can be qualitatively explained within the framework of "interlayer magnetoresistance" (ILMR).[Keywords: Graphene, Chemical Vapor Deposition, Raman Spectroscopy, Interlayer Magnetoresistance, Current-Perpendicular-to-Plane Transport] 2 Artificial layered structures often exhibit strong magnetoresistance (MR) effects that are exploited in various data storage and magnetic field sensing technologies 1 . Graphite is a naturally occurring layered material in which single graphitic layers (or "graphene") are stacked on each other. Graphene, epitaxially grown on ferromagnets (such as nickel), is particularly attractive for spintronics because such systems can potentially realize perfect spin filtering 2 and giant Rashba splitting 3 . However, CPP (current-perpendicular-toplane) MR properties of such layered graphene/ferromagnet structures are still largely underexplored. Here we consider multilayer-graphene (MLG) as-grown on nickel by chemical vapor deposition (CVD) and show that these structures exhibit large and nearly temperature-independent CPP-MR of ~ 10 4 % for a small magnetic field of ~ 2 kilogauss. This MR effect is correlated with the shape of the 2D peak and also with the occurrence of the D peak in Raman spectrum of as-grown MLG. These Raman features can be controlled by varying the CVD growth parameters. Such large negative CPP-MR, which persists even at room temperature, has hitherto not been reported in any graphitic system 4-14 . Figure 1a shows the device schematic. CVD growth of MLG is performed on 2 cm × 2 cm nickel (Ni) foils, which act as catalyst for graphene growth as well as bottom electrical contact. To ensure uniform current distribution 6 , the second contact is fabricated at the center of the top MLG surface using silver epoxy. Area of the top contact is ~ 1 mm 2 . As shown in Figure S1 (section I, Supplementary Information), the Ni substrate is polycrystalline with primarily (111) grains. Details of the fabrication process are provided in section I of Supplementary Information. Figure 1b shows a FESEM image of the as-grown large-area MLG on Ni. Raman spectra taken from three representative regions of this sample are shown in the top inset of Figure 1b. The top Raman spectrum (black line) is most commonly observed, with few occurren...

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Section: However We Note That This Model Is Not Valid In the Low Fielmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Giant Current-Perpendicular-to-Plane Magnetoresistance in Multilayer Graphene as Grown on Nickel

2014

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“…Kicked off by the experimental observation of the graphene quantum Hall effect 1,2 , fascination with massless Dirac fermions is mounting, where they appear not only in graphene but more generically in various systems such as organic metals [3][4][5] , cold atom systems in optical lattices 6 and molecular graphene 7 . Among these systems, the number of massless Dirac fermions is always even for solid state materials, which is called the "fermion doubling" 8,9 .…”

Section: Introductionmentioning

confidence: 99%

Chiral symmetry and fermion doubling in the zero-mode Landau levels of massless Dirac fermions with disorder

Kawarabayashi¹,

Honda²,

Aoki³

et al. 2013

AIP Conference Proceedings

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The effect of disorder on the Landau levels of massless Dirac fermions is examined for the cases with and without the fermion doubling. To tune the doubling a tight-binding model having a complex transfer integral is adopted to shift the energies of two Dirac cones, which is theoretically proposed earlier and realizable in cold atoms in an optical lattice. In the absence of the fermion doubling, the n = 0 Landau level is shown to exhibit an anomalous sharpness even if the disorder is uncorrelated in space (i.e., large K-K' scattering). This anomaly occurs when the disorder respects the chiral symmetry of the Dirac cone.

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Magnetotransport in organic Dirac fermion system at the quantum limit: Interlayer Hall effect and surface transport via helical edge states

Osada

2012

Physica Status Solidi (b)

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We discuss two anomalous features of interlayer magnetotransport observed in a-(BEDT-TTF) 2 I 3 in terms of massless Dirac fermions: the interlayer Hall effect and high-field interlayer magnetoresistance (MR). The former is the anomalous Hall effect, which does not depend on magnetic field strength. It depends only on field orientation showing cotu-type angle dependence. We have derived the lowest order contribution of interlayer coupling to conductivity and successfully reproduced the interlayer Hall effect as a transport phenomenon in the massless Dirac fermion system at the quantum limit. The latter is an exponential increase of interlayer MR and its follow-on saturation in higher magnetic fields. The exponential increase is evidence of the existence of a mobility gap at the Fermi level. It strongly suggests that the n ¼ 0 quantum Hall state is realized by spin splitting. In this case, two edge states with opposite spin and chirality are formed on the edge surface. The surface transport via edge states becomes dominant in interlayer transport in high enough fields, where bulk transport becomes exponentially small. The observed saturation of interlayer MR is well explained with this scenario.

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Effect of the Zero-Mode Landau Level on Interlayer Magnetoresistance in Multilayer Massless Dirac Fermion Systems

Cited by 140 publications

References 23 publications

Giant Current-Perpendicular-to-Plane Magnetoresistance in Multilayer Graphene as Grown on Nickel

Giant Current-Perpendicular-to-Plane Magnetoresistance in Multilayer Graphene as Grown on Nickel

Chiral symmetry and fermion doubling in the zero-mode Landau levels of massless Dirac fermions with disorder

Magnetotransport in organic Dirac fermion system at the quantum limit: Interlayer Hall effect and surface transport via helical edge states

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