| 1. |
- Battiato, M., et al.
(author)
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Distinctive Picosecond Spin Polarization Dynamics in Bulk Half Metals
- 2018
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In: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:7
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Journal article (peer-reviewed)abstract
- Femtosecond laser excitations in half-metal (HM) compounds are theoretically predicted to induce an exotic picosecond spin dynamics. In particular, conversely to what is observed in conventional metals and semiconductors, the thermalization process in HMs leads to a long living partially thermalized configuration characterized by three Fermi-Dirac distributions for the minority, majority conduction, and majority valence electrons, respectively. Remarkably, these distributions have the same temperature but different chemical potentials. This unusual thermodynamic state is causing a persistent nonequilibrium spin polarization only well above the Fermi energy. Femtosecond spin dynamics experiments performed on Fe3O4 by time- and spin-resolved photoelectron spectroscopy support our model. Furthermore, the spin polarization response proves to be very robust and it can be adopted to selectively test the bulk HM character in a wide range of compounds.
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| 2. |
- Beaulieu, S., et al.
(author)
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Revealing Hidden Orbital Pseudospin Texture with Time-Reversal Dichroism in Photoelectron Angular Distributions
- 2020
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In: Physical Review Letters. - : American Physical Society (APS). - 0031-9007 .- 1079-7114. ; 125:21
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Journal article (peer-reviewed)abstract
- We performed angle-resolved photoemission spectroscopy (ARPES) of bulk 2H-WSe2 for different crystal orientations linked to each other by time-reversal symmetry. We introduce a new observable called time-reversal dichroism in photoelectron angular distributions (TRDAD), which quantifies the modulation of the photoemission intensity upon effective time-reversal operation. We demonstrate that the hidden orbital pseudospin texture leaves its imprint on TRDAD, due to multiple orbital interference effects in photoemission. Our experimental results are in quantitative agreement with both the tight-binding model and state-of-the-art fully relativistic calculations performed using the one-step model of photoemission. While spin-resolved ARPES probes the spin component of entangled spin-orbital texture in multiorbital systems, we unambiguously demonstrate that TRDAD reveals its orbital pseudospin texture counterpart.
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| 3. |
- HAKANSSON, MC, et al.
(author)
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DIMER FORMATION AND ELECTRONIC-STRUCTURE ON THE GE(100)(2X1)-SB SURFACE
- 1992
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In: Surface Science. - 0039-6028 .- 1879-2758. ; 278:1-2, s. L131-L134
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Journal article (peer-reviewed)abstract
- Deposition of antimony on Ge(100)2 X 1 results in a well-ordered, highly passivated surface. From a comparison between core-level data and angle-resolved photoemission data, we conclude that the observed 2 x 1 reconstruction is caused by the formation of symmetric Sb-Sb dimers on the Ge surface.
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| 4. |
- LELAY, G, et al.
(author)
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ELECTRONIC-PROPERTIES OF CLEAVED(110) AND MBE-GROWN(100) INAS SURFACES, CLEAN AND COVERED WITH AN ULTRA-THIN AG ADLAYER
- 1993
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In: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 70-1, s. 502-506
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Journal article (peer-reviewed)abstract
- The initial electronic structure of the pseudomorphic InAs/GaAs(100) heterostructure as well as that of the Ag/InAs(110) interface at 20 K have been studied by synchrotron radiation photoelectron spectroscopy. In the first case we find that the valence band spectra show no evidence for the formation of bulk-like energy bands. In the second case we prove for the first time that upon deposition of minute amounts of Ag at low temperature onto cleaved InAs(110) substrates one induces a giant movement of the Fermi level well into the conduction band thus creating a strong two-dimensional electron channel at the surface.
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| 5. |
- LELAY, G, et al.
(author)
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SURFACE CORE-LEVEL SHIFTS ON GE(100) - C(4X2) TO 2X1 AND 1X1 PHASE-TRANSITIONS
- 1992
-
In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 45:12, s. 6692-6699
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Journal article (peer-reviewed)abstract
- By comparing, under identical experimental conditions, high-resolution synchrotron-radiation core-level photoemission spectra taken from both Ge(111) and Ge(100) samples, we establish that the decomposition of the Ge 3d lines from the clean Ge(100) 2 x 1 surface at room temperature requires two surface components shifted by -0.23 and -0.60 eV relative to the bulk one. This deconvolution is fully consistent with the asymmetric-dimer reconstruction model of this surface. We further study the reversible phase transitions that occur on this surface: 2 x 1 <--> c(4 x 2) at low temperature; 2 x 1 <--> 1 x 1 at high temperature. We show from both core-level and valence-band studies that the number of dimer bonds is essentially conserved in these transitions. We also suggest, by comparing a dimer with an Ising spin, that these transitions correspond, respectively, to an antiferromagnetic ordering at low temperatures and to a paramagnetic disordering at high temperatures.
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| 6. |
- Ndiaye, W., et al.
(author)
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Bulk electronic structure of Mn5Ge3/Ge(111) films by angle-resolved photoemission spectroscopy
- 2013
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In: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 87:16
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Journal article (peer-reviewed)abstract
- Mn5Ge3(001) thin films grown on Ge(111)-c(2 x 8) reconstructed surfaces were studied by angle-resolved photoemission using synchrotron radiation in the 14-94 eV photon energy range. The results obtained in the Gamma ALM plane and in the Gamma AHK plane are in agreement with simulations starting with band structure calculations based on the density functional theory. This provides a unique validation of band structure calculations for a proper description of the electronic properties of Mn5Ge3. Only the spectral feature very close to the Fermi level cannot be well explained by the simulation. This departure is discussed in terms of the three-dimensional nature of the sample and of correlation effects.
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| 7. |
- Ndiaye, W., et al.
(author)
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k dependence of the spin polarization in Mn5Ge3/Ge(111) thin films
- 2015
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In: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 91:12
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Journal article (peer-reviewed)abstract
- Mn5Ge3(001) thin films grown on Ge(111) were studied by angle-and spin-resolved photoemission using synchrotron radiation in the 17-40 eV photon energy range. The photoelectron spectra were simulated starting from a first-principles band-structure calculation for the ground state, using the free-electron approximation for the final states, taking into account photohole lifetime effects and k(perpendicular to) broadening plus correlation effects, but ignoring transition matrix elements. The measured spin polarizations for the various k points investigated in the Gamma MLA plane of the Brillouin zone are found to be in fair enough agreement with the simulated ones, providing a strong support to the ground-state band-structure calculations. Possible origins for the departures between either simulations and experiments or previous and present experiments are discussed.
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| 8. |
- Nicolaï, L., et al.
(author)
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Bi ultra-thin crystalline films on InAs(1 1 1)A and B substrates : A combined core-level and valence-band angle-resolved and dichroic photoemission study
- 2019
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In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 21:12
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Journal article (peer-reviewed)abstract
- The growth of Bi on both the In-terminated (A) face and the As-terminated (B) face of InAs(1 1 1) has been investigated by low-energy electron diffraction, scanning tunnelling microscopy, and photoelectron spectroscopy using synchrotron radiation. The changes upon Bi deposition of the In 4d and Bi 5d5/2 photoelectron signals allow to get a comprehensive picture of the Bi/InAs(1 1 1) interface. From the early stage the Bi growth on the A face is epitaxial, contrary to that on the B face that proceeds via the formation of islands. Angle-resolved photoelectron spectra show that the electronic structure of a Bi deposit of ≈10 bi-layers on the A face is identical to that of bulk Bi, while more than ≈30 bi-layers are needed for the B face. Both bulk and surface electronic states observed are well accounted for by fully relativistic ab initio calculations performed using the one-step model of photoemission. These calculations are used to analyse the dichroic photoemission data recorded in the vicinity of the Fermi level around the Γ&bar; point of the Brillouin zone.
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| 9. |
- Nicolai, L., et al.
(author)
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Bi ultra-thin crystalline films on InAs(111)A and B substrates: a combined core-level and valence-band angle-resolved and dichroic photoemission study
- 2019
-
In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 21:12
-
Journal article (peer-reviewed)abstract
- The growth of Bi on both the In-terminated (A) face and the As-terminated (B) face of InAs(111) has been investigated by low-energy electron diffraction, scanning tunnelling microscopy, and photoelectron spectroscopy using synchrotron radiation. The changes upon Bi deposition of the In 4d and Bi 5d(5/2) photoelectron signals allow to get a comprehensive picture of the Bi/InAs(111) interface. From the early stage the Bi growth on the A face is epitaxial, contrary to that on the B face that proceeds via the formation of islands. Angle-resolved photoelectron spectra show that the electronic structure of a Bi deposit of approximate to 10 bi-layers on the A face is identical to that of bulk Bi, while more than approximate to 30 bi-layers are needed for the B face. Both bulk and surface electronic states observed are well accounted for by fully relativistic ab initio calculations performed using the one-step model of photoemission. These calculations are used to analyse the dichroic photoemission data recorded in the vicinity of the Fermi level around the (Gamma) over bar point of the Brillouin zone.
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| 10. |
- Richter, M. C., et al.
(author)
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NiFe2O4 and Fe3O4 studied by XMCD and resonant photoemission
- 2009
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In: The European Physical Journal. Special Topics. - : Springer Science and Business Media LLC. - 1951-6355 .- 1951-6401. ; 169, s. 175-180
-
Journal article (peer-reviewed)abstract
- X-ray magnetic circular dichroism and resonant photoemission at the Fe and Ni L-2,L-3 edges have been used to investigate the electronic structure of NiFe2O4 (NFO) thin films. The results, when compared to those obtained on Fe3O4, indicate that in a 12 nm NFO film the Ni atoms occupy mainly B sites, as in bulk NFO, and that a decrease in the thickness of the film results in a modi. cation of the nickel hybridization.
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| 11. |
- Richter, MC, et al.
(author)
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Resonant photoemission at the 2p edge in compounds containing Mn with different valences
- 2006
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In: Synchrotron Radiation and Materials Science - Proceedings of the E-MRS 2005 Symposium O on Synchrotron Radiation and Materials Science (Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms). - : Elsevier BV. - 0168-583X. ; 246:1, s. 184-188
-
Conference paper (peer-reviewed)abstract
- We have investigated the Raman-Auger crossover of the Mn 2p non-radiative decays in bulk MnO. For the highest kinetic energy transition in the Mn 2p3p3p decay, Raman behaviour is observed up to approximate to 3.4 eV above the resonance energy (maximum of the L-3 absorption). In the case of the 2p3p3d and 2p3d3d transitions a similar situation occurs up to approximate to 5 eV above the resonance energy. We compare these results to those obtained on a thin MnO layer deposited on Cu, on bulk Mn and on La0.7Sr0.3MnO3. The results are discussed in terms of the screening dynamics of the Mn 2p core hole and of the metallic/insulating character of the material. (c) 2005 Elsevier B.V. All rights reserved.
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