Article

# Decay mechanisms of excited electrons in quantum-well states of ultrathin Pb islands grown on Si(111): Scanning tunneling spectroscopy and theory

Physical review. B, Condensed matter (Impact Factor: 3.66). 08/2009; DOI: 10.1103/PhysRevB.80.081409

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**ABSTRACT:**A theoretical study of the dynamical dielectric response of bulk lead at low energies is presented. The calculations are performed with full inclusion of the electronic band structure calculated by means of a first-principles pseudopotential approach. The effect of inclusion of the spin-orbit interaction in the band structure on the excitation spectra in Pb is analyzed, together with dynamical exchange-correlation and local-field effects. In general, results show significant anisotropy effects on the dielectric response of bulk Pb. At small momentum transfers along three different high-symmetry directions, the calculated excitation spectra present several peaks with strong acousticlike dispersion in the energy range below 2 eV. The analysis shows that only one of such modes existing at momentum transfers along the Γ–K direction can be interpreted as a true acousticlike plasmon, whereas all other modes are originated from the enhanced number of intraband electron-hole excitations at corresponding energies. Comparison with available optical experimental data shows good agreement.Physical review. B, Condensed matter 03/2013; 87(11). · 3.66 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Recently fabricated single-crystalline atomically flat metallic nanofilms are in fact quantum-engineered multiband superconductors. Here the multiband structure is dictated by the nanofilm thickness through the size quantization of the electron motion perpendicular to the nanofilm. This opens the unique possibility to explore superconductivity in well-controlled multi-band systems. However, a serious obstacle is the absence of a convenient and manageable theoretical tool to access new physical phenomena in such quasi–two-dimensional systems, including interplay of quantum confinement and fluctuations. Here we cover this gap and construct the appropriate multiband Ginzburg-Landau functional for nano-thin superconductors.EPL (Europhysics Letters) 05/2013; 102(2):27003. · 2.27 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**A theoretical study of the surface energy-loss function of freestanding Pb(111) thin films is presented, starting from the single monolayer case. The calculations are carried applying the linear response theory, with inclusion of the electron band structure by means of a first-principles pseudopotential approach using a supercell scheme. Quantum-size effects on the plasmon modes of the thinnest films are found in qualitative agreement with previous work based on the jellium model. For thicker films, results show a dispersionless mode at all thicknesses, in agreeement with electron energy-loss measurements. For sizeable values of the momentum, the raising of the surface plasmon with increasing thickness is retrieved.04/2013;

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