Organ-pipe modes of sodium epitaxial multilayers on Cu(001) observed by inelastic helium-atom scattering

Benedek, G.; Ellis, John; Reichmuth, Andreas M.; Ruggerone, Paolo; Schief, Hansjörg; Toennies, J. P.

doi:10.1103/physrevlett.69.2951

Cited by 90 publications

(58 citation statements)

References 13 publications

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“…This peculiar aspect of HAS spectroscopy was already known since the early measurements on Na multi-layers on Cu(001). 37 There the observed phonon frequencies were shown to correspond to the harmonics of an open-end organ pipe (organ-pipe modes), similarly to the Sezawa waves, known in seismology for geological multilayers. 38 Annealed Pb(111) films grown on Cu(111) are stable and well ordered for any thickness N L Z 3 ML, with a commensurate Pb-Cu interface in a 3/4 ratio along both symmetry crystallographic directions 31 (Fig.…”

Section: The Quantum Sonar Effectmentioning

confidence: 87%

Unveiling mode-selected electron–phonon interactions in metal films by helium atom scattering

Benedek

Bernasconi

Bohnen

et al. 2014

Phys. Chem. Chem. Phys.

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The quasi two-dimensional electron gas on a metal film can transmit to the surface even minute mechanical disturbances occurring in the depth, thus allowing the gentlest of all surface probes, helium atoms, to perceive the vibrations of the deepest atoms via the induced surface-charge density oscillations. A density functional perturbation theory (DFPT) and a helium atom scattering study of the phonon dispersion curves in lead films of up to 7 mono-layers on a copper substrate show that: (a) the electron-phonon interaction is responsible for the coupling of He atoms to in-depth phonon modes; and (b) the inelastic HAS intensity from a given phonon mode is proportional to its electron-phonon coupling. The direct determination of mode-selected electron-phonon coupling strengths has great relevance for understanding superconductivity in thin films and two-dimensional systems.

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Section: The Quantum Sonar Effectmentioning

confidence: 87%

Unveiling mode-selected electron–phonon interactions in metal films by helium atom scattering

Benedek

Bernasconi

Bohnen

et al. 2014

Phys. Chem. Chem. Phys.

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“…[57] and the electron-phonon contribution G ep has been calculated Table 11 Calculated bulk, vacuum and mixed terms to the decay rate G ee of n ¼ 1 and 2 image-potential states, for 0-2 ML of Ar/ Cu(1 0 0) by applying the Debye and Einstein model combined with the experimental value l ¼ 0:24 determined by Carlsson et al [151] for 0.95 ML Na/Cu (1 1 1). The value of the Debye energy, ho D ¼ 18 meV, has been deduced from helium-atom scattering for 1 ML of Na on Cu(1 0 0) [319] and corresponds to the lower value obtained in a first-principles calculation [320]. Debye models give G ep ¼ 9 meV.…”

Section: Overlayer States Na/cumentioning

confidence: 99%

Decay of electronic excitations at metal surfaces

Echenique

Berndt

Chulkov

et al. 2004

Surface Science Reports

436

406

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“…The signature of 1/N behavior has been observed in similar thin-film systems with a number of atomic layers grown by molecular beam epitaxy (MBE), such as Na/Cu(001). 22 And it is well understood as open-ended standing wave mode vertical to atomic planes with a linear-chain force constant model, particularly including the coupling between atomic layers and substrate. 23 For layered compounds, in principle there should exist a compression mode besides the shear mode discussed above, which is a rigid-layer vibration vertical to atomic planes.…”

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confidence: 99%

Low-frequency Raman modes and electronic excitations in atomically thin MoS2films

et al. 2012

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Atomically thin MoS2 crystals have been recognized as a quasi-2D semiconductor with remarkable physical properties. This letter reports our Raman scattering measurements on multilayer and monolayer MoS2, especially in the low-frequency range (<50 cm −1 ). We find two low-frequency Raman modes with contrasting thickness dependence. With increasing the number of MoS2 layers, one shows a significant increase in frequency while the other decreases following a 1/N (N denotes the number of unit layers) trend. With the aid of first-principles calculations we assign the former as the shear mode E 2 2g . The latter is distinguished as the compression vibrational mode, similar to the surface vibration of other epitaxial thin films. The opposite evolution of the two modes with thickness demonstrates novel vibrational modes in atomically thin crystal as well as a new and more precise way to characterize thickness of atomically thin MoS2 films. In addition, we observe a broad feature around 38 cm −1 ( 5 meV) which is visible only under near-resonance excitation and pinned at the fixed energy independent of thickness. We interpret the feature as an electronic Raman scattering associated with the spin-orbit coupling induced splitting in conduction band at K points in their Brillouin zone.

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Organ-pipe modes of sodium epitaxial multilayers on Cu(001) observed by inelastic helium-atom scattering

Cited by 90 publications

References 13 publications

Unveiling mode-selected electron–phonon interactions in metal films by helium atom scattering

Unveiling mode-selected electron–phonon interactions in metal films by helium atom scattering

Decay of electronic excitations at metal surfaces

Low-frequency Raman modes and electronic excitations in atomically thin MoS2films

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