Angle resolved photoemission valence band dispersions E(k) for gaP.

We experimentally determined the valence band dispersions E(k) along the symmetry directions ΓKX, ΓX, ΓL using angle-resolved photoemission. ΓX, ΓKX and ΓL have been studied by off-normal emission process with photon energy between 31 eV and 44 eV, while ΓKX has also been studied by normal emission process using photon energy from 31 to 85 eV. The resulting dispersion curves E(k) are compared to pseudopotential calculation. We used a direct transition model and a nearly-free electron final state approximation to interpret the main experimental features.     

Angle-resolved photoemission and experimental band structure of Cu

Two methods of angle-resolved photoemission, the energy coincidence (or triangulation) method and the appearance angle method, have been used for the absolute determination of some points in the electronic band structure of the Cu(001) and Cu(1$\text{1}$0) mirror planes. It is found that this can be done with high precision. A comparison with available band structure calculations shows that agreement is good with Burdick's non-self-consistent APW band structure, whereas larger deviations occur from more recent self-consistent band structure calculations.     

GaSe valence band structure from angle-resolved photoemission spectroscopy

Energy-wavevector dispersion curves for the GaSe valence bands obtained from angle-resolved photoemission spectra are compared with pseudopotential band calculations. It is found that the third density-of-states feature below the top of the valence bands (peak C) is related to the Ga-Se bond rather than the Ga-Ga bond. A peak not appearing in the angle-integrated spectra appears as the most intense feature at normal emission, and helps to identify completely the nature of the valence bands down to 7–8 eV below the Fermi energy.     

Surface and bulk valence band photoemission of silicon carbide

Surface and bulk valence band photoemission spectra have been obtained for silicon carbide using Zr M-zeta (151.4eV) and Mg Kα_1,2 (1253.6eV) excitation, respectively. The data have been corrected for various broadening effects using a deconvolution procedure. Spectra for single-crystal hexagonal α-SiC and for epitaxial films of cubic β-SiC on Si (1 0 0) are compared with the results of band structure calculations. Differences in the spectra for various surface reconstructions suggest the existence of surface resonances, but no surface states are observed in the bulk optical bandgap.     

Angle-resolved photoemission spectroscopy of band tails and anomalous kinetics of underdoped cuprates

The electron-phonon interaction in cuprates with c-axis polarised optical phonons, which is roughly one order of magnitude stronger than superexchange, bounds holes into mobile bipolarons. Bipolarons pin the chemical potential within the charge-transfer gap of doped Mott insulators, accounting for unusual kinetics and thermodynamics of doped cuprates such as the Nernst and giant proximity effects, pseudo-gaps, and normal-state diamagnetism. We propose that “quasi-particle” peaks, “Fermi-arcs”, and high-energy “waterfalls” in the photoemission spectra of cuprates originate from the photo-ionization matrix elements of disorder-localised band-tails in the charge-transfer gap.     

On the valence band photoemission of highT c superconductors

The valence band photoemission spectrum of highT _c -superconductors is discussed based on the half-filled single band Hubbard Hamiltonian with the strong Coulomb interaction. We discuss how to analyze these valence band and deep core level excitation spectra, concerning particularly with which orbital, Cud or Op state, a hole will occupy in the CuO₂ plane.     

Calculation of photoemission characteristics for a semiconductor model with s-like valence band and p-like conduction band

The dependence of the quantum yield and photocurrent density on Light frequency is theoretically studied for various orientations of the emission surface for the semiconductor model with simple cubic lattice and s-like valence band and p-like conduction band, and it is assumed that electron photoexcitation occurs due to indirect optical transitions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 100–104, August, 1977.     

Angle-resolved photoemission spectroscopy of perovskite-type transition-metal oxides and their analyses using tight-binding band structure

Nowadays it has become feasible to perform angle-resolved photoemission spectroscopy (ARPES) measurements of transition-metal oxides with three-dimensional perovskite structures owing to the availability of high-quality single crystals of bulk and epitaxial thin films. In this article, we review recent experimental results and interpretation of ARPES data using empirical tight-binding band-structure calculations. Results are presented for SrVO₃ (SVO) bulk single crystals and La_{1? x} Sr _x FeO₃ (LSFO) and La_{1? x} Sr _x MnO₃ (LSMO) thin films. In the case of SVO, from comparison of the experimental results with calculated surface electronic structure, we concluded that the obtained band dispersions reflect the bulk electronic structure. The experimental band structures of LSFO and LSMO were analyzed assuming the G-type antiferromagnetic state and the ferromagnetic state, respectively. We also demonstrated that the intrinsic uncertainty of the electron momentum perpendicular to the crystal surface is important for the interpretation of the APRES results of three-dimensional materials.     

On the interpretation of valence band photoemission spectra of NiO

The valence band photoemission spectrum and the L₃VV Auger spectrum of NiO are compared. The satellite found in the valence band of NiO and other Ni compounds is interpreted as an unscreened 3d⁷ final state, whereas the main d-emission is a 3d⁷ final state screened by a d electron in an exitonic state.     

Internal X-ray photoemission in aluminum: Excitation of electrons from the valence band

Measurements are reported of Al valence-electron excitation by Ka_1,2 X-rays internally generated in evaporated specimens by electron bombardment. The X-ray photoelectron energy distribution is consistent with the u.v. distribution of Huen and Wooten. Weak structures are found in the energy distribution at positions corresponding to those in the calculated density of states.     

Giant enhancement of the valence band photoemission intensity in γ-Ce

We have observed a giant enhancement of the Ce valence band emission above the 4d absorption threshold. It is interpreted as being due to autoionization decay following 4d¹⁰4f¹ → 4d⁹4f² transitions. By taking advantage of this effect we have been able to make a determination of the location of the 4f levels in γ-Ce.     

Angle-resolved photoemission study for double Ag nanofilm structures

We have carried out an angle-resolved photoemission study for Ag/Cu/Ag/Cu(1 1 1) system in order to investigate the electronic coupling between the two quantum-well (QW) states in the double Ag nanofilm structures. It is found that the outer nanofilm thickness dependence of QW state in double Ag nanofilm structures can be explained as the electronic coupling through the thin Cu barrier layer between the QW states in the inner and outer Ag nanofilms. It is also found that the coupling strength depends on the Cu barrier thickness. From these results, we discuss the electronic coupling between the two QW states in the double Ag nanofilm structures.     

Angle-resolved photoemission and LEED from rare-earth metals

Angle-resolved photoemission and LEED studies of single-crystal surfaces of the rare-earth metals are still relatively few in number. The reasons for this are outlined and comparisons are made between the procedures used to obtain clean and well-ordered surfaces suitable for study. Valence-band photoemission spectra are compared with surface electronic structure and photocurrent calculations in order to identify surface and bulk features. Core-level spectroscopy indicates that the 5p levels of the lanthanides show intensity variations with emission angle that are not explicable in terms of a simple core-level shift. Although the 4p levels of Y have some band character, detailed comparison of the 4p photoemission lineshape with those produced by photocurrent calculations enables the surface core-level shift to be determined. Quantitative LEED studies of close-packed (0001) surfaces show essentially a bulk-terminated structure for Sc, a structural reconstruction of the divalent surface of Sm and a magnetic reconstruction of ferromagnetic Gd. The more open (11 0) and (10 0) surfaces of all the rare-earth metals studied undergo extensive reconstructions into a close-packed structure almost identical to that of a (0001) surface. Angle-resolved photoemission and LEED have yet to distinguish between these structures, indicating a reconstruction depth of at least five atomic layers.     

Direct and roughness-induced indirect transitions in photoemission from silver films

One-photon and two-photon electron emission spectra from vapour deposited rough and smooth Ag films are compared. Photoemission from rough films is strongly enhanced due to the participation of localized surface plasmons (LSP). A theory is outlined that successfully estimates the enhancement and predicts that LSP-initiated photoemission would involve momentum non-conserving transitions.     

Electron correlation effects in the valence band photoemission spectra of cooper dichloride

He I, He II and Al Kα photoemission measurements of the valence band of CuCl₂ are reported. The presence of the 3d⁸-like satellite indicates the strong correlation effects in the final state and the breakdown of the one-particle model. It is shown that the reduction of the satellite intensity in the valence band compared with the core hole emission is caused by the delocalization of the photo-hole. The satellite intensity in resonance with the super-Coster-Kronig decay is calculated.     

Strength of plasmon satellites in the valence band photoemission spectra of metals

The strength of the first bulk plasmon satellite in the valence band photo-emission spectra of simple metals has been calculated for the dispersionless plasmon model. It is found that due to the mobility of the final state hole in the valence band, the strength of the plasmon satellite is lowered compared to that of the core state. This conclusion is qualitatively confirmed by an independent experiment of Van Attekum and Trooster.     

The valence band of some light rare-earth metals studied by photoemission spectroscopy

The valence bands of La, Ce, Pr, and Nd have been studied by ultraviolet photoelectron spectroscopy (UPS) (He II, hv=40.8 eV) and compared to results from X-ray photoelectron spectroscopy (XPS)(Mg Kα_{1, 2}). The energy positions of the $\text{4?}$ levels are in good agreement with earlier XPS results and calculations based on estimates from optical and thermodynamic data. The widths of the sd bands and the $\text{4?}$ levels and the relative emission intensities are discussed.     

Hydrogen chemisorption on W {110}: Angle-resolved photoemission

Normal photoemission spectra (k_∥ = 0) from a W {110} surface reveal 2 major resonances during hydrogen chemisorption, at 2.0 and 4 eV below the Fermi level, E_F. The former appears at 300 K during filling of the low coverage β₂ state, and the latter grows as the β₁ state is filled. Detailed spectra obtained along the $\text{}\text{?}$gS and $\text{}\text{?}$gD azimuths are reported, showing additional resonances at ~0.5, 1,3,6 and ~7 eV below E_F. A structural model is proposed, based on a consideration of the present results in relation to RHEED and HRELS data, for the H-saturated surface in which a p(1 × 2) structure is formed, at a H: surface W ratio of unity, with β₁ adatoms occupying a close bridge position and β₂ adatoms in a 3-fold hollow site.