One-dimensional versus two-dimensional electronic states in vicinal surfaces

Ortega, J. E.; Ruiz-Oses, M.; Cordón, J; Mugarza, Aitor; Kuntze, J.; Schiller, Frederik

doi:10.1088/1367-2630/7/1/101

Cited by 25 publications

(35 citation statements)

References 25 publications

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“…2(c), has a free-electron-like character: it can be reconstructed by ellipses (rather than circles) around the ÿ points of the (111) terraces and, in addition, by shifted replica along the where d 1:55 nm is the interchain distance. Such repeated structures also have been found for a variety of vicinal metallic surfaces [16,17]. For better orientation we marked the ÿ points and the SBZ of the (111) surface in Fig.…”

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confidence: 68%

Coupled Pb Chains on Si(557): Origin of One-Dimensional Conductance

et al. 2008

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The Pb=Si557 system exhibits a strong anisotropy in conductance below 78 K, with the evolution of a characteristic chain structure. Here we show, using angle-resolved photoemission, that chain ordering results in complete Fermi-like nesting in the direction normal to the chains; in addition, the domain structure along the chains forms split-off valence bands with mesoscopic Fermi wavelengths which induce the 1D conductance without further instabilities at low temperatures. DOI: 10.1103/PhysRevLett.100.076802 PACS numbers: 73.20.At, 68.65.ÿk, 73.21.ÿb, 73.25.+i Confinement of electrons in low-dimensional structures induces intriguing transport phenomena and electronic properties. This scenario of strongly interacting electrons is described within the framework of a Luttinger liquid (LL) rather than by a Fermi liquid (FL) [1]. In an intuitive picture, this changeover is intimately related to the geometry of the structure; i.e., the interaction between electrons is enhanced in low-dimensional systems. An obvious strategy of making one-dimensional (1D) conductors is to use anisotropic solid state bulk materials like Bechgaard salts [2,3] or, as shown recently, Ca 2 Ru 2 O 7 [4,5]. Anisotropic adsorbate structures, realized on (vicinal) surfaces, are even more flexible, because the structure can be controlled on an atomic scale, and the electronic structure can be changed gradually by varying the degree of localization, e.g., by changing terrace widths. Submonolayer coverages of Ag and Au on vicinal Si(111) surfaces form chain structures showing indeed localized states perpendicular to the chain direction [6 -8]. However, these weakly interacting systems often undergo instabilities, e.g., Peierls-or Mott-Hubbard driven phase transitions into insulating states at low temperature (see, e.g., [9] ), and the 1D character of charge carriers is rarely established in transport measurements.The Pb=Si557 system is unique in this respect since macroscopic conductance measurements [10,11] reveal a slightly anisotropic temperature activated conductance above T c 78 K. Below this temperature the conductance switches reversibly to quasi-1D and metallic along the step direction, while in the perpendicular direction conductance is indistinguishable from the residual conductance of the substrate. In contrast to all systems exhibiting quasi 1D-conductance properties investigated so far, this system turns into a quasi-1D metallic conductance state at low temperatures with no indications of further instabilities.This intriguing behavior requires an explanation in terms of the interplay of the geometric and electronic structure across the phase transition. Here using angleresolved photoemission (ARPES), we demonstrate that the interplay of the overlayer structure and the substrate leads to an electronically stabilized arrangement of chain structures and has direct consequences on the formation and filling of electronic bands that results in the observed transport properties. In particular, we demonstrate 1D conductance is a direct co...

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confidence: 68%

Coupled Pb Chains on Si(557): Origin of One-Dimensional Conductance

et al. 2008

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“…This is also expected for a SSS [13]. Because the slope of the ASP dispersion is, as a first approximation, proportional to the Fermi velocity, the ASP is directly affected.…”

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confidence: 51%

“…Because the slope of the ASP dispersion is, as a first approximation, proportional to the Fermi velocity, the ASP is directly affected. Indeed, quantum confinement and energy gap opening become visible on stepped Au and Cu surfaces once step-step interactions become sufficiently small [13][14][15]. For stepped Au(111) this occurs for terrace widths exceeding d c ¼ 20 Å [16].…”

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confidence: 99%

“…In order to model the physical scenario on the (788) surface we took into account the transformation of the Au (111) SSS band into the QW subbands observed in photoemission experiments [13]. First, a nearly free electron gas model is employed to accurately reproduce the Au (111) SSS dispersion (see Fig.…”

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confidence: 99%

“…Second, a simple but realistic step potential (a plateau for terraces and a short-range reflective potential at steps) similar to that proposed in Ref. [13] was used to obtain the SSS subbands. The resulting electronic structure in the extended band scheme is shown in Fig.…”

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Anisotropic Dispersion and Partial Localization of Acoustic Surface Plasmons on an Atomically Stepped Surface: Au(788)

et al. 2014

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Understanding acoustic surface plasmons (ASPs) in the presence of nanosized gratings is necessary for the development of future devices that couple light with ASPs. We show here by experiment and theory that two ASPs exist on Au(788), a vicinal surface with an ordered array of monoatomic steps. The ASPs propagate across the steps as long as their wavelength exceeds the terrace width, thereafter becoming localized. Our investigation identifies, for the first time, ASPs coupled with intersubband transitions involving multiple surface-state subbands. DOI: 10.1103/PhysRevLett.113.186804 PACS numbers: 78.68.+m, 73.20.At, 73.20.Mf, 79.20.Uv Acoustic surface plasmons (ASPs) originate from the excitation of a 2D electron gas whenever it is effectively screened by an underlying 3D electron gas [1]. Contrary to sheet plasmons, characterized by a square-root-like dependence on the wave vector [2], ASPs have a linear soundlike dispersion and hence frequency-independent group and phase velocities. These excitations are very promising for future applications in plasmonics because the speed, and thus the wavelength, of ASPs is 3 orders of magnitude lower than that of light, permitting us in principle to locate plasmonic excitations on the scale of a few nanometers. A hypothetical polychromatic ASP signal would indeed propagate without distortion, allowing for accurate signal processing.Suitable 2D electron gases are associated with the Shockley surface state (SSS) or any other 2D free electron gas. Linearly or quasilinearly dispersing ASPs have indeed been reported for bare and O-covered Be(0001) [3,4], Cu(111) [5,6], and Au(111) [7,8], as well as for graphene deposited on metal substrates. Generally speaking, they are expected to exist whenever two slightly spatially separated electron gases interact sufficiently strongly [9,10]. Ab initio density-response calculations [3,7,11] confirmed their existence on Be, Cu, Ag, and Au surfaces.The dispersion curves of ASP and light do not, however, per se cross at clean surfaces, so a momentum source is needed to realize coupling of the ASP with photons; this can be realized by, e.g., a grating. However, the short wavelength of the ASP requires realization of this grating on the atomic scale. For example, it can be generated by a regular array of atomic steps, as provided by vicinal surfaces of single crystals. Nanostructuring, however, implies concomitant generation of atomic defects, so it is necessary to understand how defects and confinement in nanosized regions modify the ASP dispersion. As a first step, we recently demonstrated that the ASP survives damage induced by heavy ion bombardment on Cu (111) [12], at least as long as the SSS itself survives the treatment. The question we address here is how the plasmonic structure of a bare Au(111) surface is transformed by a regular array of atomic steps. Combining experiment and density-response calculations, we demonstrate the existence of two plasmonic modes at the Au(788) surface both parallel and perpendicular to the steps, due...

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