Theory of Scanning Tunneling Spectroscopy of Magnetic Adatoms in Graphene

Uchoa, Bruno; Yang, Ling; Tsai, Shan-Wen; Peres, N. M. R.; Neto, A. H. Castro

doi:10.1103/physrevlett.103.206804

Cited by 98 publications

(126 citation statements)

References 23 publications

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“…Quantum interference effects, like the Fano effect, are extremely sensitive to atomistic details such as symmetries of the involved orbitals or specific impurity positions. Upon completion of this work we became aware of recent works of Zhuang et al, 34 Uchoa et al, 35 and Saha et al 36 that address related questions for the case of s-wave magnetic impurities.…”

Section: Discussionmentioning

confidence: 99%

Theory of Fano resonances in graphene: The influence of orbital and structural symmetries on STM spectra

et al. 2010

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We theoretically investigate Fano factors arising in local spectroscopy of impurity resonances in graphene. It is demonstrated that Fano line shapes can strongly differ from the antiresonances usually found on metal surfaces. Graphene's highly symmetric Fermi points make this effect particularly sensitive to the detailed atomistic structure and orbital symmetries of the impurity. After a model discussion based on an Anderson impurity coupled to an electron bath with linearly vanishing density of states, we present first-principles calculations of Co adatoms on graphene. For Co above the center of a graphene hexagon, we find that the two-dimensional E 1 representation made of d xz , d yz orbitals is likely responsible for the hybridization and ultimately Kondo screening for cobalt on graphene. Anomalously large Fano q factors depending strongly on the orbitals involved are obtained. For a resonant s-wave impurity, a similarly strong adsorption site dependence of the q factor is demonstrated. These anomalies are striking examples of quantum-mechanical interference related to the Berry phase inherent to the graphene band structure.

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Section: Discussionmentioning

confidence: 99%

Theory of Fano resonances in graphene: The influence of orbital and structural symmetries on STM spectra

et al. 2010

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“…We choose parameters from Ref. [56] as α = −0.185|t| and t α = 0.37|t|. This gives a resonant level within the energy interval of consideration.…”

Section: Simple Defectsmentioning

confidence: 99%

Dual-probe spectroscopic fingerprints of defects in graphene

et al. 2014

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Recent advances in experimental techniques emphasize the usefulness of multiple scanning probe techniques when analyzing nanoscale samples. Here, we analyze theoretically dual-probe setups with probe separations in the nanometer range, i.e., in a regime where quantum coherence effects can be observed at low temperatures. In a dual-probe setup the electrons are injected at one probe and collected at the other. The measured conductance reflects the local transport properties on the nanoscale, thereby yielding information complementary to that obtained with a standard one-probe setup (the local density of states). In this work we develop a real-space Green's function method to compute the conductance. This requires an extension of the standard calculation schemes, which typically address a finite sample between the probes. In contrast, the developed method makes no assumption of the sample size (e.g., an extended graphene sheet). Applying this method, we study the transport anisotropies in pristine graphene sheets, and analyze the spectroscopic fingerprints arising from quantum interference around single-site defects, such as vacancies and adatoms. Furthermore, we demonstrate that the dual-probe setup is a useful tool for characterizing the electronic transport properties of extended defects or designed nanostructures. In particular, we show that nanoscale perforations, or antidots, in a graphene sheet display Fano-type resonances with a strong dependence on the edge geometry of the perforation.

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“…Similarly, the signatures of magnetic adatoms in graphene when probed by scanning tunneling spectroscopy have also been investigated using a theoretical approach. 13 This method again avails of Green function methods within the linear dispersion regime. We anticipate that our approach may allow for an extension of such studies to energies beyond the linear dispersion regime.…”

Section: Applicationmentioning

confidence: 99%

Electronic structure of graphene beyond the linear dispersion regime

Power

Ferreira

2011

Phys. Rev. B

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Among the many interesting features displayed by graphene, one of the most attractive is the simplicity with which its electronic structure can be described. The study of its physical properties is significantly simplified by the linear dispersion relation of electrons in a narrow range around the Fermi level. Unfortunately, the mathematical simplicity of graphene electrons is limited only to this narrow energy region and is not very practical when dealing with problems that involve energies outside the linear dispersion part of the spectrum. In this communication we remedy this limitation by deriving a set of closed-form analytical expressions for the real-space single-electron Green function of graphene which is valid across a large fraction of the energy spectrum. By extending to a wider energy range the simplicity with which graphene electrons are described, it is now possible to derive more mathematically transparent and insightful expressions for a number of physical properties that involve higher energy scales. The power of this new formalism is illustrated in the case of the magnetic (RKKY) interaction in graphene.

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Theory of Scanning Tunneling Spectroscopy of Magnetic Adatoms in Graphene

Cited by 98 publications

References 23 publications

Theory of Fano resonances in graphene: The influence of orbital and structural symmetries on STM spectra

Theory of Fano resonances in graphene: The influence of orbital and structural symmetries on STM spectra

Dual-probe spectroscopic fingerprints of defects in graphene

Electronic structure of graphene beyond the linear dispersion regime

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