Fourier-transform scanning tunnelling spectroscopy: the possibility to obtain constant-energy maps and band dispersion using a local measurement

Simon, Laurent; Bena, Cristina; Vonau, F.; Cranney, Marion; Aubel, Dominique

doi:10.1088/0022-3727/44/46/464010

Cited by 83 publications

(119 citation statements)

References 104 publications

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“…4(d) and 4(e), which show how the scattering events observed in FT dI/dU maps correspond to the filled area obtained by the intersection of two constant-energy cuts taken at the same energy and translated with respect to each other by the scattering vector. 32 We would like to emphasize that, contrary to previous measurements on Bi 2 have been detected close to the Dirac point for Bi 2 Te 3 . In Ref.…”

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confidence: 66%

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Visualizing spin-dependent bulk scattering and breakdown of the linear dispersion relation in Bi2Te3

et al. 2013

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We performed a scanning tunneling spectroscopy investigation of the electronic properties of the topological insulator Bi 2 Te 3 in the energy range between −200 and +700 meV with respect to the Fermi level. For unoccupied states, tunneling into topological surface states dominates. Analysis of Fourier-transformed (FT) dI/dU maps allowed us to obtain their energy dispersion relation and to visualize the breakdown of the linear dispersion relation typical of massless particles. For occupied states, no signature of scattering events involving surface states can be detected. FT dI/dU maps reveal in this case two scattering vectors pointing along the M and K directions. Both are identified with scattering events within bulk states. Interestingly, vectors pointing along K which correspond to bulk backscattering events have a length longer than the minimum distance necessary to match opposite pockets on a constant energy cut. Comparison with calculated spin-resolved constant-energy cuts shows that this is a direct consequence of the chiral spin texture present in bulk states when their energy and momentum are close to the resonances of the spin-polarized topological surface states. The recent discovery of topological insulators (TIs), a new class of materials insulating in the bulk but conducting on the surface, has opened a new route towards spintronic devices. 1-3Topological surface states of TIs are gapless and, contrary to the trivial surface states usually found at surfaces in metals and semiconductors, cannot be destroyed by the presence of defects and adsorbates as long as time-reversal symmetry is preserved. [4][5][6][7][8] Topological surface states are characterized by a linear energy-momentum dispersion relation, and their charge carriers can be described by a Dirac-like equation for massless particles rather than the Schrödinger equation.9 Consequently, their phase velocity is coincident with the group velocity, and carriers at different energies are all moving with same speed. Because of the Kramers degeneracy theorem, opposite spin directions are degenerate only at high-symmetry points of the surface Brillouin zone where both time-and space-reversal symmetry is preserved: the so-called Dirac points. Above and below these points the spin is perpendicularly locked to the momentum, resulting in a chiral spin texture, 10 spin currents intrinsically tied to charge currents, 11 and forbidden backscattering. 12,13 This results in an increased spin coherence time, an important quantity for spintronic devices in which the information is encoded by the spin degree of freedom.14 In addition to possible technological applications, their spin and electronic structures make these materials a platform to search for exotic phenomena like Majorana fermions 15 and magnetic monopoles. 16 However, to what extent the electronic structure of topological states resembles the one typical of massless particles has not been clearly experimentally addressed so far. The same holds true concerning the spin-related properties of thes...

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confidence: 66%

“…One factor often neglected in the interpretation of QPI experiments is that the signal not only depends on the initial and final states but also may be strongly influenced by the symmetry and extension of defects. In the joint-density-of-states (JDOS) approximation, 32 the observed signal is given by…”

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confidence: 99%

Visualizing spin-dependent bulk scattering and breakdown of the linear dispersion relation in Bi2Te3

et al. 2013

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“…The radius of these rings is 2k, where k is the wave vector of the Dirac particles at an energy E relative to E F and it is measured with respect to the K point of the graphene BZ. The deviation of the shape of these ringlike features from the circle for large positive bias voltages is due to the trigonal warping at the energies far away from E D , as was shown in theoretical calculations [33]. Figure 3 shows the extracted dispersions of the wave vector k gathered from a series of dI/dV maps measured for BiAg 2 and GNF/BiAg 2 , as discussed above [see the STM image of the border between two regions in Fig.…”

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confidence: 62%

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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“…We used Fourier-transformed scanning tunneling spectroscopy and model calculations to resolve the band structures of the 2DEG. [21][22][23][24][25] We determined quantitatively how the band bottom, bandwidth, and band gap are tailored by the periodicity of the supramolecular networks and by the molecule-substrate interaction. Moreover, we found that two bands touch at the K points of the network Brillouin zone, forming Dirac cones.…”

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confidence: 99%

Tuning two-dimensional band structure of Cu(111) surface-state electrons that interplay with artificial supramolecular architectures

Wang

Tan

et al. 2013

Phys. Rev. B

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We report on the modulation of two-dimensional (2D) bands of Cu(111) surface-state electrons by three isostructural supramolecular honeycomb architectures with different periodicity or constituent molecules. Using Fourier-transformed scanning tunneling spectroscopy and model calculations, we resolved the 2D band structures and found that the intrinsic surface-state band is split into discrete bands. The band characteristics including band gap, band bottom, and bandwidth are controlled by the network unit cell size and the nature of the molecule-surface interaction. In particular, Dirac cones emerge where the second and third bands meet at the K points of the Brillouin zone of the supramolecular lattice.

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Fourier-transform scanning tunnelling spectroscopy: the possibility to obtain constant-energy maps and band dispersion using a local measurement

Cited by 83 publications

References 104 publications

Visualizing spin-dependent bulk scattering and breakdown of the linear dispersion relation in Bi2Te3

Visualizing spin-dependent bulk scattering and breakdown of the linear dispersion relation in Bi2Te3

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

Tuning two-dimensional band structure of Cu(111) surface-state electrons that interplay with artificial supramolecular architectures

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