Wave-Function Mapping of Graphene Quantum Dots with Soft Confinement

Subramaniam, Dinesh; Libisch, Florian; Li, Y.; Pauly, Christian; Герингер, Виктор; Reiter, R.; Mashoff, T.; Liebmann, Marcus; Burgdörfer, Joachim; Busse, Carsten; Michely, Thomas; Mazzarello, Riccardo; Pratzer, M.; Morgenstern, Markus

doi:10.1103/physrevlett.108.046801

Cited by 116 publications

(131 citation statements)

References 48 publications

(35 reference statements)

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“…S4 of the Supplemental Material). This effect is contrary to the previously observed results for graphene adsorption on Au(111) [25,26], Ag(111) [26,36,37], Cu(111) [38], and Ir(111) [16,39], where an upward energy shift for the metallic surface states was reported and explained by a stronger localization of the wave function of the metallic surface state producing an increase of Pauli repulsion at the interface. This effect leads to an increase of the energy of the electrons and consequently to the upward energy shift of the surface state.…”

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confidence: 99%

Local electronic properties of the graphene-protected giant Rashba-split BiAg2 surface

et al. 2017

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We report the preparation of an interface between graphene and a strong Rashba-split BiAg 2 surface alloy and an investigation of its structure as well as the electronic properties by means of scanning tunneling microscopy/spectroscopy and density functional theory calculations. Upon evaluation of the quasiparticle interference patterns, an unperturbed linear dispersion for the π band of n-doped graphene is observed. Our results also reveal the intact nature of the giant Rashba-split surface states of the BiAg 2 alloy, which demonstrate only a moderate downward energy shift due to the presence of graphene. This effect is explained in the framework of density functional theory by an inward relaxation of the Bi atoms at the interface and subsequent delocalization of the wave function of the surface states. Our findings demonstrate a realistic pathway to prepare a graphene-protected giant Rashba-split BiAg 2 for possible spintronic applications. DOI: 10.1103/PhysRevB.95.155428 Graphene has attracted much attention due to its unique transport, electronic, and elastic properties [1][2][3]. Taking into account these characteristics, many practical applications of graphene have been proposed. The most promising are graphene-based touch screens, which will potentially replace indium-tin-oxide (ITO-) based screens in the future [4,5], batteries and supercapacitors [6][7][8], and composite materials [9,10]. Above that, a single atom thick graphene layer can effectively protect the underlying material against oxidation and/or corrosion [11,12]. This property is particularly exciting when graphene is deposited or formed on the surface of a ferromagnet or a material which exhibits strong spin-orbit interaction [13][14][15][16][17][18][19]. Here, interfacial contact between graphene and the respective material might lead to the appearance of different new phenomena in graphene and at the interface, such as induced magnetism in graphene [20][21][22], possible induced spin-orbit splitting of the graphene π states [23,24], conservation of spin-polarized electron emission from the underlying ferromagnetic material [13,15], etc.Previously published works on the adsorption of graphene on the surfaces of heavy materials, such as Ir (111) and Au(111), demonstrate that such contacts only weakly modify the dispersion of the spin-orbit split surface states of the metal surface. Adsorption of graphene merely leads to a rigid shift of the respective surface states to smaller binding energies [16,25,26], which was explained by the stronger localization of the surface state wave function, leading to a corresponding energy shift. At the same time, the intercalation of Au in the graphene/Ni(111) interface leads to the appearance of induced spin-orbit splitting of the graphene π states (up to ≈100 meV) as a result of the hybridization of these states and valence band states of the underlying heavy metal [23,24]. Here, the energetically unfavorable model of diluted Au atoms underneath graphene on Ni (111) Here, we report the fabrication of ...

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Local electronic properties of the graphene-protected giant Rashba-split BiAg2 surface

et al. 2017

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“…Other morphologies apart from nanotriangles should yield similar high levels of nonlinear response, particularly when their edges are predominantly armchair. Graphene nanoislands with sizes comparable to those considered here have already been fabricated using various methods [36][37][38] , although they lack precise control over size and shape, which limits their applicability to nonlinear photonic technologies. Alternatively, a bottom-up approach based upon chemical self-asembly of molecular precursors provides better degree of control over the sizes and edge configurations [39][40][41] .…”

Section: Discussionmentioning

confidence: 99%

Electrically tunable nonlinear plasmonics in graphene nanoislands

2014

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Nonlinear optical processes rely on the intrinsically weak interactions between photons enabled by their coupling with matter. Unfortunately, many applications in nonlinear optics are severely hindered by the small response of conventional materials. Metallic nanostructures partially alleviate this situation, as the large light enhancement associated with their localized plasmons amplifies their nonlinear response to record high levels. Graphene hosts long-lived, electrically tunable plasmons that also interact strongly with light. Here we show that the nonlinear polarizabilities of graphene nanoislands can be electrically tuned to surpass by several orders of magnitude those of metal nanoparticles of similar size. This extraordinary behaviour extends over the visible and near-infrared spectrum for islands consisting of hundreds of carbon atoms doped with moderate carrier densities. Our quantummechanical simulations of the plasmon-enhanced optical response of nanographene reveal this material as an ideal platform for the development of electrically tunable nonlinear optical nanodevices. T he well established field of nonlinear photonics hosts a vast number of applications, including spatial and spectral control of laser light, all-optical signal processing, ultrafast switching and sensing 1,2 . Because the efficiencies of nonlinear optical processes are generally poor, considerable effort has been devoted towards seeking materials that can display nonlinear effects at low light intensities and ultrafast response times [2][3][4] . For this purpose, plasmonic nanostructures have been particularly attractive due to their ability to generate high local intensity enhancements through strong confinement of electromagnetic fields 3,5,6 , leading to second-harmonic polarizabilities as high as B10 À 27 esu (electrostatic units) per atom, as measured for noble metal nanoparticles 3 , and even beating the best molecular chromophores 3,7,8 . However, although localized plasmons can be customized through the size, shape and surrounding environment of the metal nanostructures 5 , they suffer from low lifetimes and lack post-fabrication tunability 9 .Doped graphene has recently attracted much attention as an alternative plasmonic material capable of sustaining electrically tunable optical excitations with long lifetimes [9][10][11][12][13][14][15][16][17][18] . The existence of gate-tunable plasmons in graphene has been confirmed by THz 13,14 and mid-infrared 15,16 spectroscopies, while optical nearfield microscopy has been used to image them in real space 17,18 . Efforts to extend the plasmonic response of graphene to the visible and near-infrared regimes are currently underway 12 . In addition, graphene has been predicted to display intense nonlinearity due to its anharmonic charge-carrier dispersion relation 19 . Recent four-wave mixing 20 , Kerr effect 21 , and thirdharmonic generation (THG) 22 experiments already confirm a large third-order response in this material in the undoped, plasmon-free state. Graphene plasmons co...

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“…Among the different electronic Dirac devices, the chaotic Dirac quantum dot (DQD), also called chaotic Dirac billiard (DB), has received a significant highlight [4,18,[24][25][26][27][28][29][30][31][32][33], due to its universal characteristics. In the search for such universal properties, the Ref.…”

Section: Introductionmentioning

confidence: 99%

Fluctuation phenomena in chaotic Dirac quantum dots: Artificial atoms on graphene flakes

2016

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We develop the stub model for the Dirac Quantum Dot, an electron confining device on a grapheme surface. Analytical results for the average conductance and the correlation functions are obtained and found in agreement with those found previously using semiclassical calculation. Comparison with available data are presented. The results reported here demonstrate the applicability of Random Matrix Theory in the case of Dirac electrons confined in a stadium.

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Wave-Function Mapping of Graphene Quantum Dots with Soft Confinement

Cited by 116 publications

References 48 publications

Local electronic properties of the graphene-protected giant Rashba-split BiAg2 surface

Local electronic properties of the graphene-protected giant Rashba-split BiAg2 surface

Electrically tunable nonlinear plasmonics in graphene nanoislands

Fluctuation phenomena in chaotic Dirac quantum dots: Artificial atoms on graphene flakes

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