Strong spin–orbit splitting in graphene with adsorbed Au atoms

Ma, Dongwei; Li, Zhongyao; Yang, Zhongqin

doi:10.1016/j.carbon.2011.08.055

Cited by 81 publications

(67 citation statements)

References 46 publications

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“…However, recent studies have indicated that the curvature arising from the cylindrical geometry can enhance spin-orbit coupling due to hybridization among neighboring carbon atoms [19,20] . Further, the strength of the spin-orbit interaction is strongly dependent on the substrate and the species adsorbed on the graphitic surface [21] .…”

Section: Introductionmentioning

confidence: 99%

Spin Filtering through Single‐Wall Carbon Nanotubes Functionalized with Single‐Stranded DNA

Alam

Pramanik

2015

Adv Funct Materials

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Abstract.High spin polarization materials or spin filters are key components in spintronics, a niche subfield of electronics where carrier spins play a functional role. Carrier transmission through these materials is "spin selective" i.e. these materials are able to discriminate between "up" and "down" spins. Common spin filters include transition metal ferromagnets and their alloys, with typical spin selectivity (or, polarization) ~ 50% or less. Here we consider carrier transport in an archetypical one-dimensional molecular hybrid in which a single wall carbon nanotube (SWCNT) is wrapped around by single stranded deoxyribonucleic acid (ssDNA). By magnetoresistance measurements we show that this system can act as a spin filter with maximum spin polarization approaching ~ 74% at low temperatures, significantly larger than transition metals under comparable conditions. Inversion asymmetric helicoidal potential of the charged ssDNA backbone induces a Rashba spin-orbit interaction in the SWCNT channel and polarizes carrier spins. Our results are consistent with recent theoretical work that predicted spin dependent conductance in ssDNA-SWCNT hybrid. Ability to generate highly spin polarized carriers using molecular functionalization can lead to magnet-less and contactless spintronic devices in the future. This can eliminate the conductivity mismatch problem and open new directions for research in organic spintronics. 2 1. Introduction.

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Section: Introductionmentioning

confidence: 99%

Spin Filtering through Single‐Wall Carbon Nanotubes Functionalized with Single‐Stranded DNA

Alam

Pramanik

2015

Adv Funct Materials

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“…Graphene is an ideal material, if methods, which do not require chemical functionalization, to enhance its weak spin-orbit coupling (SOC) are devised 5 . The recent predictions of proximity enhanced SOC in graphene decorated with metallic adatoms, where electrons tunnel from graphene to adatoms and back, thereby locally enhancing the SOC, open up a new path [6][7][8][9][10] . The proximity-induced SOC in graphene decorated with physisorbed metallic adatoms is unique and different from hydrogenated graphene.…”

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confidence: 99%

Giant spin Hall effect in graphene grown by chemical vapour deposition

et al. 2014

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Advances in large-area graphene synthesis via chemical vapour deposition on metals like copper were instrumental in the demonstration of graphene-based novel, wafer-scale electronic circuits and proof-of-concept applications such as flexible touch panels. Here, we show that graphene grown by chemical vapour deposition on copper is equally promising for spintronics applications. In contrast to natural graphene, our experiments demonstrate that chemically synthesized graphene has a strong spin-orbit coupling as high as 20 meV giving rise to a giant spin Hall effect. The exceptionally large spin Hall angle B0.2 provides an important step towards graphene-based spintronics devices within existing complementary metal-oxide-semiconductor technology. Our microscopic model shows that unavoidable residual copper adatom clusters act as local spin-orbit scatterers and, in the resonant scattering limit, induce transverse spin currents with enhanced skew-scattering contribution. Our findings are confirmed independently by introducing metallic adatoms-copper, silver and gold on exfoliated graphene samples.

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“…This so called Rashba-Bychkov effect [7] is further enhanced for surface alloys, such as Bi/Ag(111) [8,9], Pb/Ag(111) [10], and Sb/Ag(111) [11], leading to a giant Rashba splitting. Moreover, recent studies point out the possibility of an induced extrinsic Rashba splitting in graphene on Au [12][13][14]. Compared with the intrinsic spin-orbit coupling (SOC) in graphene, which is in the range of 50 μeV [15][16][17], the Rashba-type splitting induced by the presence of Au has recently been reported to reach 100 meV [14].…”

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confidence: 99%

“…In addition to graphenerelated and Au-related scattering, we observe QPI features due to the interband scattering between graphene and Au states, which allow for the direct quantitative determination of the spin splitting of the Au(111) surface state at the local scale by STM. We also comment on the possibility to observe the recently reported giant Rashba splitting of graphene [12][13][14] in the graphene/Au system by means of QPI.Experiments were performed in a two-chamber ultrahigh vacuum (UHV) system (base pressure p 5 × 10 −11 mbar) equipped with an Omicron Cryogenic scanning tunneling microscope. All measurements were performed at 10 K in constant-current mode using electrochemically etched and UHV flash-annealed polycrystalline tungsten tips.…”

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confidence: 99%

Rashba splitting of graphene-covered Au(111) revealed by quasiparticle interference mapping

et al. 2014

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We report on low-temperature scanning tunneling spectroscopy measurements on epitaxial graphene flakes on Au(111). We show that using quasiparticle interference (QPI) mapping, we can discriminate between the electronic systems of graphene and Au(111). Beyond the scattering vectors, which can be ascribed to the elastic scattering within each of the systems, we observe QPI features related to the scattering process between graphene states and the Au(111) surface state. This additional interband scattering process at the graphene/Au(111) interface allows the direct quantitative determination of the Rashba-splitting of the Au(111) surface state, which cannot be evaluated from QPI measurements on pure Au(111). This experiment demonstrates a unique local spectroscopic approach to investigate the Rashba-split bands at weakly interacting epitaxial graphene/substrate interfaces. The spin-orbit (SO) interaction in combination with broken space inversion symmetry at surfaces leads to a spin splitting of surface states in heavy metals as experimentally observed by photoemission for instance at the Au(111) [1][2][3], Bi(111) [4,5], and Sb(111) [6] surfaces. This so called Rashba-Bychkov effect [7] is further enhanced for surface alloys, such as Bi/Ag(111) [8,9], Pb/Ag(111) [10], and Sb/Ag(111) [11], leading to a giant Rashba splitting. Moreover, recent studies point out the possibility of an induced extrinsic Rashba splitting in graphene on Au [12][13][14]. Compared with the intrinsic spin-orbit coupling (SOC) in graphene, which is in the range of 50 μeV [15][16][17], the Rashba-type splitting induced by the presence of Au has recently been reported to reach 100 meV [14].Although the Rashba-split bands are readily visible in angle-resolved photoemission experiments [1-3], their observation at the local scale by means of scanning tunneling microscopy (STM) employing quasiparticle interference (QPI) mappings is challenging. Within such an experiment, one probes the local density of states (LDOS) oscillations generated by QPIs arising from elastic scattering between different momentum eigenstates. These standing wave patterns give rise to characteristic features in Fourier-transformed local density of states (FT-LDOS) maps, which can be understood using joint density of states (JDOS) considerations [18][19][20], i.e., the simple evaluation of principle scattering vectors connecting states on the constant-energy contour (CEC) of the system. However, in the case of spin-split bands only scattering between states with the same spin polarization occurs, making it impossible to reconstruct the full spin-split band structure by analysis of QPI [21][22][23][24]. In particular cases, the presence of both spin-split and spin-degenerate surface state bands allows interband transitions, which yield the information about the Rashba splitting [25]. In Au(111), however, only spinconserved backscattering within the surface state is observed, which masks the actual spin splitting, hence necessitating a different approach for the local observat...

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Strong spin–orbit splitting in graphene with adsorbed Au atoms

Cited by 81 publications

References 46 publications

Spin Filtering through Single‐Wall Carbon Nanotubes Functionalized with Single‐Stranded DNA

Spin Filtering through Single‐Wall Carbon Nanotubes Functionalized with Single‐Stranded DNA

Giant spin Hall effect in graphene grown by chemical vapour deposition

Rashba splitting of graphene-covered Au(111) revealed by quasiparticle interference mapping

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