Symmetry of standing waves generated by a point defect in epitaxial graphene

Simon, Laurent; Bena, Cristina; Vonau, F.; Aubel, Dominique; Nasrallah, H.; Habar, M.; Peruchetti, J.C.

doi:10.1140/epjb/e2009-00142-3

Cited by 54 publications

(81 citation statements)

References 28 publications

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“…We emphasize that a few publications have tried so far to give a description of the different features in the experimental FT-LDOS images of epitaxial graphene. 27,28,30,31 However, a poor resolution in k space was partly limiting such analysis. In a report published in 2008, some of us have shown that it was possible to evidence fine structures in FT-LDOS data with improved quality.…”

Section: High-resolution Stm Results On Monolayer Graphene On Sicmentioning

confidence: 99%

“…[27][28][29][30][31][32][34][35][36][37][38][39][40][41][42] Because of the topology of the FS pockets, coupling between states with opposite q F in each pocket [ Fig. 1(d)] is highly favored.…”

Section: Quasiparticle Scattering In Graphene: Intravalley and Imentioning

confidence: 99%

“…41,42 It has been used to derive the dispersion relation on bilayer (BL) graphene, 28,30 and more tentatively on ML graphene on SiC(0001). 28 In Ref.…”

Section: Introductionmentioning

confidence: 99%

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Role of pseudospin in quasiparticle interferences in epitaxial graphene probed by high-resolution scanning tunneling microscopy

et al. 2012

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Pseudospin, an additional degree of freedom emerging in graphene as a direct consequence of its honeycomb atomic structure, is responsible for many of the exceptional electronic properties found in this material. This paper is devoted to providing a clear understanding of how graphene's pseudospin impacts the quasiparticle interferences of monolayer (ML) and bilayer (BL) graphene measured by low-temperature scanning tunneling microscopy and spectroscopy. We have used this technique to map, with very high energy and space resolution, the spatial modulations of the local density of states of ML and BL graphene epitaxially grown on SiC(0001), in presence of native disorder. We perform a Fourier transform analysis of such modulations including wave vectors up to unit vectors of the reciprocal lattice. Our data demonstrate that the quasiparticle interferences associated to some particular scattering processes are suppressed in ML graphene, but not in BL graphene. Most importantly, interferences with 2q F wave vector associated to intravalley backscattering are not measured in ML graphene, even on the images with highest resolution where the graphene honeycomb pattern is clearly resolved. In order to clarify the role of the pseudospin on the quasiparticle interferences, we use a simple model which nicely captures the main features observed in our data. The model unambiguously shows that graphene's pseudospin is responsible for such suppression of quasiparticle interference features in ML graphene, in particular for those with 2q F wave vector. It also confirms scanning tunneling microscopy as a unique technique to probe the pseudospin in graphene samples in real space with nanometer precision. Finally, we show that such observations are robust with energy and obtain with great accuracy the dispersion of the π bands for both ML and BL graphene in the vicinity of the Fermi level, extracting their main tight-binding parameters.

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Section: High-resolution Stm Results On Monolayer Graphene On Sicmentioning

confidence: 99%

Section: Quasiparticle Scattering In Graphene: Intravalley and Imentioning

confidence: 99%

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Role of pseudospin in quasiparticle interferences in epitaxial graphene probed by high-resolution scanning tunneling microscopy

et al. 2012

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“…The magnetic-field strength is assumed weak enough so that we could take the energy levels as spin degenerate. The dispersion curves can be experimentally observed via scanning tunnelling microscopy (Simon et al 2009). The tunnelling current flowing through the microscope tip is proportional to the LDOS given by…”

Section: Modelmentioning

confidence: 99%

Graphene nanoribbons in criss-crossed electric and magnetic fields

Roslyak

Gumbs

Huang

2010

Phil. Trans. R. Soc. A.

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Graphene nanoribbons (GNRs) in mutually perpendicular electric and magnetic fields are shown to exhibit dramatic changes in their band structure and electron-transport properties. A strong electric field across the ribbon induces multiple chiral Dirac points, closing the semiconducting gap in armchair GNRs. A perpendicular magnetic field induces partially formed Landau levels as well as dispersive surface-bound states. Each of the applied fields on its own preserves the even symmetry E k = E −k of the sub-band dispersion. When applied together, they reverse the dispersion parity to be odd, which gives E e,k = −E h,−k , and mix the electron and hole sub-bands within the energy range corresponding to the change in potential across the ribbon. This leads to oscillations of the ballistic conductance within this energy range. The broken time-reversal symmetry provides dichroism in the absorption of the circularly polarized light. As a consequence, one can observe electrically enhanced Faraday rotation, since the edges of the ribbon provide formation of the substantial density of states.

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“…Not surprisingly, then, many theory groups have recently devoted attention to the prospect of RKKY interactions. [63][64][65][66][67][68][69][70][71][72][73][74] They and others pointed out a variety of complicating issues and idiosyncrasies of mono-layer graphene, such as the bipartite nature of the lattice (leading to ferromagnetic or repulsive coupling for impurities on the same hexagonal, Bravais sublattice of the honeycomb graphene lattice 63,64 and antiferromagnetic or attractive coupling when on opposite Bravais sublattices, 64,65,68,69 ), the vanishing density of states at the Fermi level in undoped and ungated lattices, the suppression of backscattering (leading to R −3 rather than R −2 decay 75 ), 63,64 the role of electron-electron interactions, 70 etc. Usually the adsorbates are taken in atop sites but sometimes in bridge sites above bonds or hollow sites at the center of the hexagon.…”

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confidence: 99%

Anisotropic surface-state-mediated RKKY interaction between adatoms

Patrone

Einstein

2012

Phys. Rev. B

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Motivated by recent numerical studies of Ag on Pt(111), we derive an expression for the RKKY interaction mediated by surface states, considering the effect of anisotropy in the Fermi edge. Our analysis is based on a stationary phase approximation. The main contribution to the interaction comes from electrons whose Fermi velocity vF is parallel to the vector R connecting the interacting adatoms; we show that in general, the corresponding Fermi wave-vector kF is not parallel to R. The interaction is oscillatory; the amplitude and wavelength of oscillations have angular dependence arising from the anisotropy of the surface state band structure. The wavelength, in particular, is determined by the projection of this kF (corresponding to vF) onto the direction of R. Our analysis is easily generalized to other systems. For Ag on Pt(111), our results indicate that the RKKY interaction between pairs of adatoms should be nearly isotropic and so cannot account for the anisotropy found in the studies motivating our work. However, for metals with surface state dispersions similar to Be(1010), we show that the RKKY interaction should have considerable anisotropy.

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Symmetry of standing waves generated by a point defect in epitaxial graphene

Cited by 54 publications

References 28 publications

Role of pseudospin in quasiparticle interferences in epitaxial graphene probed by high-resolution scanning tunneling microscopy

Role of pseudospin in quasiparticle interferences in epitaxial graphene probed by high-resolution scanning tunneling microscopy

Graphene nanoribbons in criss-crossed electric and magnetic fields

Anisotropic surface-state-mediated RKKY interaction between adatoms

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