One-step Model Of Photoemission Research Articles

Multiple-scattering theoretical approach to magnetic dichroism and spin polarization in angle-resolved core-level photoemission

Magnetic dichroism in spin- and angle-resolved core-level photoemission is investigated within the relativistic one-step model of photoemission based on multiple-scattering theory. Photoelectron scattering in emission from $3p$ levels of low-index Fe and Ni surfaces is found to affect intensities, dichroism, and photoelectron spin polarizations considerably, in particular in off-normal emission. In general, the calculated spectra agree well with their experimental counterparts in spectral shape, size of the dichroic signal, and spin polarization. Magnetic circular dichroism in a chiral setup is analyzed theoretically using appropriately defined asymmetries. Further, core-level energy positions and photoemission are compared with those obtained within an atomic model.

Electronic properties of epitaxial Cu films on Pt(100)

Abstract In this contribution we present angular resolved UPS valence band spectra of epitaxial Cu(100) films of 1 to 13 ml thickness grown on Pt(100). The growth structure of the Cu(100) films was determined by LEED and STM. The corresponding ARUPS Cu(3d) valence band spectra are compared with theoretical calculations within the framework of a fully relativistic one-step model of photoemission.

Observation of magnetic splitting in XPS MnL-spectra of Co MnSn and Pd MnSn Heusler alloys

The XPS MnL-spectra of Co2MnSn, a nearly half-metallic ferromagnet (HMF) and Pd2MnSn were investigated. The most drastical feature of the spectra observed is the well-dened magnetic splitting of the Mn 2p3=2 ,2 p 1 = 2 lines. This gives direct evidence of the existence of well-dened local magnetic moments in Heusler alloys in comparison with other itinerant-electron ferromagnets. The calculations of Mn2p XPS spectra of these materials were carried out using a fully relativistic generalization of the one-step model of photoemission and show excellent agreement with experiment.

Magnetic dichroism in valence-band x-ray photoemission spectroscopy

The availability of tunable synchrotron radiation of well defined polarization allowed it to refine more or less all kind of electronic spectroscopies during the last years [1]. In particular detailed information on magnetic solids [1] could be obtained by investigating the various types of spin-orbit induced magnetic dichroism. In the case of core level photo emission spectroscopy magnetic dichroism could be observed for transition metal as well as rare earth metal systems by using circularly [2], linearly [3] and even unpolarized [4] radiation in a spin-integrated as well as spin-resolved way. A corresponding theoretical description has been developed by various authors starting from an itinerant [5] or atomic description [6] of the underlying electronic structure. The linear and circular forms of magnetic dichroism in valence band (VB) photoemission has been investigated experimentally by several groups [7] in the UV regime. A proper theoretical description of these experiments on transition metal systems could be given by Feder and coworkers [8] by extending the one-step model of photo emission to the spin-polarized relativistic situation. These investigations done with polarized radiation give an extremely detailed insight into the electronic structure of the investigated material because of the various selection rules. For the X-ray regime, however, the k-selection rule is no more present [9]. Nevertheless, as will be demonstrated below, a pronounced magnetic dichroism still occurs in that case — even for angular integrated spectra.

Ab initio angle-resolved photoemission intensity calculations for MgO

The one-step model of photoemission considerably advanced in its range of applicability due to its recent generalization to the case of several atoms per unit cell. It allows the calculation of angle-resolved ultraviolet photoemission and Bremsstrahlung isochromat spectra from compounds. Here we present calculated angle-resolved photoemission spectra from the MgO(100) surface and compare our results with corresponding experimental data.

Full potential photoemission theory: application to MgO and CaO

The full potential photoemission theory is applied for the first time to the alkaline-earth oxides MgO and CaO. This theory is a straightforward generalization of the one-step model of photoemission for the case of anisotropic, space-filling potentials and several atoms per unit cell. It allows the calculation of angle-resolved ultraviolet photoemission (ARUPS) and bremsstrahlung isochromat spectra (ARBIS) from compounds. The calculations are based on space-filling crystal potentials calculated self-consistently with the full potential Korringa-Kohn-Rostoker (KKR) band structure method. As a first application of this generalized one-step model we present calculated angle-resolved photoemission spectra from the (100) surfaces of MgO and CaO and compare the results with corresponding experimental data. The results include the self-consistent band structures and a comparison of muffin-tin and full potential results. The overall agreement between experiment and theory is excellent.

Full-potential photoemission theory.

The one-step model of photoemission is generalized to the case of space-filling potential cells of arbitrary shape. The resulting method differs from the usual muffin-tin formalism in an improved treatment of the single-center scattering, already successfully employed in full-potential Korringa-Kohn-Rostoker band-structure calculations. Finally it results in generalized matrix elements for the four contributions to the photocurrent that take the full nonspherical crystal potential into account. This generalized photoemission theory will be useful for the calculation of (inverse) photoemission spectra of ordered systems, such as pure elemental solids, compounds, and alloys, in a unified manner.

Theory of temperature-dependent photoemission in 3d-band ferromagnets: Application to Ni(110) and Ni(111).

The effects of electron correlations and phonons on the temperature dependence of ultraviolet photoemission and bremsstrahlung isochromat spectra of ferromagnetic Ni are investigated. The spin- and temperature-dependent photocurrent is calculated in the framework of a generalized one-step model of photoemission. Phonons are then into account via temperature-dependent phase shifts. The hole state of photoemission is described by an energy-, spin-, and temperature-dependent self-energy, which rests on a combination of density-functional theory and a Hubbard-type multiband model

The unoccupied states of tungsten(001) and tungsten(110): theory and experiment

The results of relativistic photocurrent calculations, based on the one-step model of photoemission, used here to simulate inverse photoemission spectroscopy (IPES) experiments from the W(001) and W(110) surfaces are presented. The isochromat IPES spectra, for photon energies ranging between 15 and 30 eV, were recorded for electrons incident normal to the (001) and (110) crystal surfaces, corresponding to transitions in the Gamma H and Gamma N directions of the three-dimensional Brillouin zone respectively. This combined theoretical and experimental study is used to investigate the electronic structure, in particular the bulk electronic structure, of these systems. The calculated spectra are found to be in good overall agreement with the corresponding experimental results. The origins of the remaining discrepancies between theory and experiment are discussed.

The temperature dependence of the inverse photoemission from copper surfaces

The temperature dependence of the intensity of inverse photoemission transitions into bulk and surface states has been studied on Cu(100), (110) and (111) surfaces. On Cu(100) and (111) the temperature dependence can be fitted very well with a Debye-Waller law where the mean square displacements of the surface atoms increase linearly with temperature. On Cu(110) we find an enhancement of the mean square displacements above 400 K in agreement with other scattering experiments. Through the comparison of the same bulk transition on different surfaces we find a strong influence of surface vibrations on the intensities of bulk transitions. The one-step model of photoemission and the result of phonon calculations for surface vibrations have been combined to give a theoretical description of the measured temperature dependencies.