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type:text, The Compton profile of the Ba doped silicon clathrate (Ba 8Si46) has been studied using the high-resolution Compton scattering technique. The Compton profile is sensitive to the change of wave functions, and the good agreement between experiment and theory validates a theoretical prediction. A difference Compton profile between the Ba doped and nondoped clathrates (Si136) has been experimentally obtained and compared with that of a first-principles band structure calculation. The experiment and calculation show excellent agreement with respect to the overall shape in the profile. Analyses of partial density of the states (DOS) predict that, by doping Ba atoms into the Si cages, Ba 6s electrons are transferred into Ba 5d orbitals that are strongly hybridized with Si 3p orbitals. The hybridized states form a sharp peak of the DOS in close vicinity of the Fermi level, which plays an important role for the occurrence of superconductivity in Ba 8Si46.

type:text, The silicon clathrate compound Ba8Si46 shows superconductivity below the critical temperature (Tc) of 8K, and the Tc decreases monotonically with doping Ag. In order to reveal effects of Ag doping on the electronic states, we have applied soft x-ray photoemission spectroscopy to Ag-doped silicon clathrate compounds Ba8AgxSi46-x (x=0,1,3,6). The valence band photoemission spectra show that a Ba 5d-derived state at the Fermi level (EF), which is prominently observed in Ba8Si46, decreases with increasing Ag content. The reduction in the peak intensity at EF with increasing Ag content is therefore in accord with the decrease of Tc in Ba8AgxSi46-x. Band structure calculation using local-density approximation reproduces the observed valence band spectra of x=0 and 6. The Si 2p and Ba 4d core-level photoemission spectra demonstrate that the valence electron of Si is attracted to the Ag site in x=1 and the 5d electron of Ba inside the Si24 cage is further donated to Ag in x≥3. Hence, Ag doping leads to the reduction of the peak at EF.

The Compton profile of the Ba doped silicon clathrate (Ba 8Si46) has been studied using the high-resolution Compton scattering technique. The Compton profile is sensitive to the change of wave functions, and the good agreement between experiment and theory validates a theoretical prediction. A difference Compton profile between the Ba doped and nondoped clathrates (Si136) has been experimentally obtained and compared with that of a first-principles band structure calculation. The experiment and calculation show excellent agreement with respect to the overall shape in the profile. Analyses of partial density of the states (DOS) predict that, by doping Ba atoms into the Si cages, Ba 6s electrons are transferred into Ba 5d orbitals that are strongly hybridized with Si 3p orbitals. The hybridized states form a sharp peak of the DOS in close vicinity of the Fermi level, which plays an important role for the occurrence of superconductivity in Ba 8Si46.

The silicon clathrate compound Ba8Si46 shows superconductivity below the critical temperature (Tc) of 8K, and the Tc decreases monotonically with doping Ag. In order to reveal effects of Ag doping on the electronic states, we have applied soft x-ray photoemission spectroscopy to Ag-doped silicon clathrate compounds Ba8AgxSi46-x (x=0,1,3,6). The valence band photoemission spectra show that a Ba 5d-derived state at the Fermi level (EF), which is prominently observed in Ba8Si46, decreases with increasing Ag content. The reduction in the peak intensity at EF with increasing Ag content is therefore in accord with the decrease of Tc in Ba8AgxSi46-x. Band structure calculation using local-density approximation reproduces the observed valence band spectra of x=0 and 6. The Si 2p and Ba 4d core-level photoemission spectra demonstrate that the valence electron of Si is attracted to the Ag site in x=1 and the 5d electron of Ba inside the Si24 cage is further donated to Ag in x≥3. Hence, Ag doping leads to the reduction of the peak at EF.

The Compton profile of the Ba doped silicon clathrate (Ba 8Si46) has been studied using the high-resolution Compton scattering technique. The Compton profile is sensitive to the change of wave functions, and the good agreement between experiment and theory validates a theoretical prediction. A difference Compton profile between the Ba doped and nondoped clathrates (Si136) has been experimentally obtained and compared with that of a first-principles band structure calculation. The experiment and calculation show excellent agreement with respect to the overall shape in the profile. Analyses of partial density of the states (DOS) predict that, by doping Ba atoms into the Si cages, Ba 6s electrons are transferred into Ba 5d orbitals that are strongly hybridized with Si 3p orbitals. The hybridized states form a sharp peak of the DOS in close vicinity of the Fermi level, which plays an important role for the occurrence of superconductivity in Ba 8Si46.

The silicon clathrate compound Ba8Si46 shows superconductivity below the critical temperature (Tc) of 8K, and the Tc decreases monotonically with doping Ag. In order to reveal effects of Ag doping on the electronic states, we have applied soft x-ray photoemission spectroscopy to Ag-doped silicon clathrate compounds Ba8AgxSi46-x (x=0,1,3,6). The valence band photoemission spectra show that a Ba 5d-derived state at the Fermi level (EF), which is prominently observed in Ba8Si46, decreases with increasing Ag content. The reduction in the peak intensity at EF with increasing Ag content is therefore in accord with the decrease of Tc in Ba8AgxSi46-x. Band structure calculation using local-density approximation reproduces the observed valence band spectra of x=0 and 6. The Si 2p and Ba 4d core-level photoemission spectra demonstrate that the valence electron of Si is attracted to the Ag site in x=1 and the 5d electron of Ba inside the Si24 cage is further donated to Ag in x≥3. Hence, Ag doping leads to the reduction of the peak at EF.

We report theoretical studies of dielectric functions and quasi-particle lifetimes in Ag by means of ab initio full-potential linear ‘muffin-tin’-orbitals LMTO GW and LAPW approaches. We show that the methods provide better description of the dielectric functions then the previous studies based on local density approximation of the density functional theory. In particular, the calculated electron energy loss function contains plasmon absorption peak which was absent in earlier calculations. The computed lifetimes of holes in the highest d-states are in good agreement with the experimental data. At lower energy large discrepancy between calculated and experimental data is observed which we refer to neglecting the vertex corrections.

We present measurements of the spectral function of aluminum and lithium using high-energy electron momentum spectroscopy. For aluminum the quasiparticle peaks show clear asymmetries and significant satellite intensity that extends over a wide region to larger binding energies. The intensity distribution is not well described by band structure calculations. These data are described only by calculations based on the manybody cumulant expansion scheme. The measured momentum distribution at the Fermi level agrees with the theoretical one within 0.03 a.u. For lithium a bandwidth of 3.0 eV is obtained.

The silicon clathrate compound Ba8Si46 shows superconductivity below the critical temperature (Tc) of 8K, and the Tc decreases monotonically with doping Ag. In order to reveal effects of Ag doping on the electronic states, we have applied soft x-ray photoemission spectroscopy to Ag-doped silicon clathrate compounds Ba8AgxSi46-x (x=0,1,3,6). The valence band photoemission spectra show that a Ba 5d-derived state at the Fermi level (EF), which is prominently observed in Ba8Si46, decreases with increasing Ag content. The reduction in the peak intensity at EF with increasing Ag content is therefore in accord with the decrease of Tc in Ba8AgxSi46-x. Band structure calculation using local-density approximation reproduces the observed valence band spectra of x=0 and 6. The Si 2p and Ba 4d core-level photoemission spectra demonstrate that the valence electron of Si is attracted to the Ag site in x=1 and the 5d electron of Ba inside the Si24 cage is further donated to Ag in x≥3. Hence, Ag doping leads to the reduction of the peak at EF.

The Compton profile of the Ba doped silicon clathrate (Ba 8Si46) has been studied using the high-resolution Compton scattering technique. The Compton profile is sensitive to the change of wave functions, and the good agreement between experiment and theory validates a theoretical prediction. A difference Compton profile between the Ba doped and nondoped clathrates (Si136) has been experimentally obtained and compared with that of a first-principles band structure calculation. The experiment and calculation show excellent agreement with respect to the overall shape in the profile. Analyses of partial density of the states (DOS) predict that, by doping Ba atoms into the Si cages, Ba 6s electrons are transferred into Ba 5d orbitals that are strongly hybridized with Si 3p orbitals. The hybridized states form a sharp peak of the DOS in close vicinity of the Fermi level, which plays an important role for the occurrence of superconductivity in Ba 8Si46.