Real-space multiple scattering method for angle-resolved photoemission and valence-band photoelectron diffraction and its application to Cu(111)

Krüger, Péter; Pieve, Fabiana Da; Osterwalder, Jürg

doi:10.1103/physrevb.83.115437

Cited by 28 publications

(27 citation statements)

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“…It comes from the simplification of the sum over delocalized valence states through the so called optical theorem in RSMS [22] and it contains the bandstructure information. The matrix elements M ω,q iLσ (k) are given by…”

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confidence: 99%

“…The B jL ′ (k) are the key quantities in the RSMS approach and represent the multiple scattering amplitudes of the continuum state k ≡ (kσ k ) [22]. The matrix elements A jL ′ ,iL (ǫ k σ k , ǫ v σ) are given by the sum of the direct radiative process (A D ), the resonant process with direct Coulomb decay (A C ) and the resonant process with the exchange decay (A X ), see Eq.…”

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confidence: 99%

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First-Principles Calculations of Angle-Resolved and Spin-Resolved Photoemission Spectra of Cr(110) Surfaces at the2p−3dCr Resonance

Pieve

Krüger

2013

Phys. Rev. Lett.

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A first principles approach for spin and angle resolved resonant photoemission is developed within multiple scattering theory and applied to a Cr(110) surface at the 2p-3d resonance. The resonant photocurrent from this non ferromagnetic system is found to be strongly spin polarized by circularly polarized light, in agreement with experiments on antiferromagnetic and magnetically disordered systems. By comparing the antiferromagnetic and Pauli-paramagnetic phases of Cr, we explicitly show that the spin polarization of the photocurrent is independent of the existence of local magnetic moments, solving a long-standing debate on the origin of such polarization. New spin polarization effects are predicted for the paramagnetic phase even with unpolarized light, opening new directions for full mapping of spin interactions in macroscopically non magnetic or nanostructured systems.PACS numbers: 78.20. Bh,75.20.Ls, In recent years, the theoretical description of absorption/photoemission spectroscopy in the X-ray region has been boosted by the merge of density functional theory (DFT) with many body approaches such as dynamical mean field theory [1, 2], many body perturbation theory [3][4][5] and by the development of time-dependent DFT [6]. However, second order processes, like resonant inelastic X-ray scattering (RIXS) and resonant photoemission (RPES), remain a major challenge for theory. For RPES, existing approaches are semiempirical [7][8][9][10], based on a well defined two-holes final state and on small clusters, and thus do not take into account the delocalization of intermediate states, the bandstructure of the system and multiple scattering effects in the propagation of photoelectrons.The huge experimental output from RPES on correlated materials [7,[11][12][13][14][15][16] and the intriguing quest for a determination of local magnetic properties put forward by pioneering experiments [14][15][16] call for advancements in the theoretical description of this spectroscopy. In experiments on CuO and Ni, it was shown that the RPES photocurrent with circular polarized light is spin polarized in antiferromagnets [14,15] and Curie paramagnets [16]. It was claimed that a specific combination of spin resolved spectra provides a direct measure of the local magnetic moments [14][15][16]. The issue is of fundamental importance in the search for a tool to access the local magnetic properties in antiferromagnetic, magnetically disordered and/or nanostructured systems at their crossover with the transition temperature. The interpretation was however rejected on the basis of symmetry analysis [17], but explicit calculations predicting the lineshape and intensity of such fundamental signal are still lacking and remain highly desirable.In this letter, we present the first ab-initio method for RPES in solids, based on a combined formulation within the real space multiple scattering (RSMS) approach [18,19] and DFT, and its application to Cr(110) at the 2p-3d resonance. By comparing the antiferromagnetic (AFM) and Pauli-paramagnetic (...

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First-Principles Calculations of Angle-Resolved and Spin-Resolved Photoemission Spectra of Cr(110) Surfaces at the2p−3dCr Resonance

Pieve

Krüger

2013

Phys. Rev. Lett.

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“…The angular intensity distribution of the photoelectrons is furthermore modulated by interference effects of scattered photoelectron waves and, thereby, provides direct information about the atomic structure of the surface. This effect is called photoelectron diffraction and can be seen in angular distributions excited by x rays (XPD) [17,18] or ultraviolet light (UPD) [19][20][21]. We demonstrate that the dynamics of the full process can be investigated by tr-ARPES and photoelectron diffraction using light from a high-harmonic laboratory source.…”

Section: Introductionmentioning

confidence: 99%

“…It was shown previously that the full valence band must be integrated in energy in order to avoid effects due to electronic dispersion [19,20]. The regions probed by the photoemission process are sketched in Fig.…”

Section: Time-resolved Photoelectron Diffractionmentioning

confidence: 99%

Access to phases of coherent phonon excitations by femtosecond ultraviolet photoelectron diffraction

et al. 2016

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Coherent phonons are an excellent tool to investigate the interplay between electronic and structural dynamics. The displacive excitation of coherent phonons in elemental bismuth is one of the most widely studied processes for this purpose. We employ time-resolved photoelectron diffraction to access the structural dynamics by recording the photoemission intensity from one initial state as a function of emission angle. In comparison with tight-binding and single-scattering cluster calculations, this allows electronic and structural effects to be disentangled. Hence, the full dynamics of the hot electron gas and of coherently excited phonons can be accessed in a single experiment. As a major result the phase lag between the coherent phonons and the modulation of the electronic structure can be determined with high precision. The phonon phase lag with respect to the modulation of the electronic structure is about 2.85±0.21 rad, thus significantly smaller than . The difference is not due to phonon decay by energy dissipation into low-energy modes, but rather caused by the very early evolution of the highly excited electron distribution. Coherent phonons are an excellent tool to investigate the interplay between electronic and structural dynamics. The displacive excitation of coherent phonons in elemental bismuth is one of the most widely studied processes for this purpose. We employ time-resolved photoelectron diffraction to access the structural dynamics by recording the photoemission intensity from one initial state as a function of emission angle. In comparison with tight-binding and single-scattering cluster calculations, this allows electronic and structural effects to be disentangled. Hence, the full dynamics of the hot electron gas and of coherently excited phonons can be accessed in a single experiment. As a major result the phase lag between the coherent phonons and the modulation of the electronic structure can be determined with high precision. The phonon phase lag with respect to the modulation of the electronic structure is about 2.85 ± 0.21 rad, thus significantly smaller than π . The difference is not due to phonon decay by energy dissipation into low-energy modes, but rather caused by the very early evolution of the highly excited electron distribution.

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“…(5) was carried out numerically. The real space multiple scattering code [38,52] is interfaced with self-consistent all electron potentials obtained with the band structure method LMTO. In this work on Fe(010), the atomic potentials were computed in the local spin density approximation for bulk ferromagnetic Fe.…”

Section: Theoretical Formulationmentioning

confidence: 99%

Real-space Green's function approach to angle-resolved resonant photoemission: Spin polarization and circular dichroism in itinerant magnets

Pieve

Krüger

2013

Phys. Rev. B

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A first principles approach, based on the real space multiple scattering Green's function method, is presented for spin-and angle-resolved resonant photoemission from magnetic surfaces. It is applied to the Fe(010) valence band photoemission excited with circularly polarized X-rays around the Fe L3 absorption edge. When the photon energy is swept through the Fe 2p − 3d resonance, the valence band spectra are strongly modified in terms of absolute and relative peak intensities, degree of spin-polarization and light polarization dependence. New peaks in the spin-polarized spectra are identified as spin-flip transitions induced by exchange decay of spin-mixed core-holes. By comparison with single atom and band structure data, it is shown that both intra-atomic and multiple scattering effects strongly influence the spectra. We show how the different features linked to states of different orbital symmetry in the d band are differently enhanced by the resonant effect. The appearance and origin of circular dichroism and spin polarization are analyzed for different geometries of light incidence and electron emission direction, providing guidelines for future experiments.PACS numbers: 78.20. Bh, 78.20.Ls, In the last decade, magnetic circular dichroism (MCD) and spin polarization studies in resonant inelastic X-ray scattering (RIXS) and resonant photoemission (RPES) have acquired great importance in the study of magnetic and correlated materials. Such spectroscopies probe respectively the radiative and non radiative autoionization decay of a core hole, and the signal can be strongly enhanced with respect to the non resonant mode. The element and orbital selectivity of core level resonant spectroscopies allows to access higher order multipoles which are left unexplored by MCD in X-ray absorption (XAS) [1][2][3][4][5][6], to distinguish and enhance specific electronic excitations and satellites [7,8], collective magnetic excitations [9], ultrafast and charge transfer dynamics [10][11][12] and to detect quadrupolar transitions towards localized empty states [13,14]. In particular, RPES has recently been applied to several correlated materials [15][16][17][18][19] and full two dimensional angular scans of resonantly emitted electrons in moderately correlated materials have also been carried out [20,21]. These works, together with earlier pioneering studies [22,23] on local magnetic properties in macroscopically non magnetic systems, demonstrate the importance of RPES and the need for an advancement in the theoretical description of this spectroscopy, which is the main aim of this work.RPES is in principle an autoionization channel of the * Electronic address: fabiana.dapieve@gmail.com more general process called resonant Auger decay. Depending on whether the core-excited electron participates or not in the Auger decay, the process is termed either participator or spectator channel. In the participator channel the one hole final state is degenerate with the one in direct valence band photoemission (PES, or ARPES if angle reso...

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Real-space multiple scattering method for angle-resolved photoemission and valence-band photoelectron diffraction and its application to Cu(111)

Cited by 28 publications

References 24 publications

First-Principles Calculations of Angle-Resolved and Spin-Resolved Photoemission Spectra of Cr(110) Surfaces at the2p−3dCr Resonance

First-Principles Calculations of Angle-Resolved and Spin-Resolved Photoemission Spectra of Cr(110) Surfaces at the2p−3dCr Resonance

Access to phases of coherent phonon excitations by femtosecond ultraviolet photoelectron diffraction

Real-space Green's function approach to angle-resolved resonant photoemission: Spin polarization and circular dichroism in itinerant magnets

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