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Transfer of spectral weight across the magnetic transition in CoO: novel results from high-energy angle-resolved photoelectron spectroscopy
KTH, School of Information and Communication Technology (ICT), Material Physics.
KTH, School of Information and Communication Technology (ICT), Material Physics.ORCID iD: 0000-0002-3086-9642
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(English)Manuscript (preprint) (Other academic)
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Other Engineering and Technologies not elsewhere specified
Identifiers
URN: urn:nbn:se:kth:diva-13915OAI: oai:DiVA.org:kth-13915DiVA: diva2:328212
Note
QC 20100702Available from: 2010-07-02 Created: 2010-07-02 Last updated: 2010-07-02Bibliographically approved
In thesis
1. Investigations of Transition Metal Systems: Angle-Resolved Photoelectron Spectroscopy at Low and High Energy
Open this publication in new window or tab >>Investigations of Transition Metal Systems: Angle-Resolved Photoelectron Spectroscopy at Low and High Energy
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The work presented in this thesis aims at achieving an increased understanding of the electronic structure of materials whose properties are to a large extent governed by transition metals. All studies are based on data from angle-resolved photoelectron spectroscopy (ARPES) employed on the valence band of the studied systems. In some cases spectroscopic data have also been combined with numerical electronic structure studies performed using a density functional theory computer code.

Five of the studies make extensive use of the benefits provided by performing angle-resolved photoelectron spectroscopy at high photon energies. When probed with soft x-ray photons, the near Fermi edge distribution of spectral weight in Nd2-xCexCuO4 and La2-x-yNdySrxCuO4 display significant differences as compared to similar studies performed in the 20-100 eV range of photon energies. This effect can be attributed to the approximate two-fold increase in probing depth as compared to the low photon energy case.

However, high photon energies not only give increased probing depth, it also enables a straightforward interpretation of ARPES data from fully three-dimensional compounds in terms of valence band energy dispersion. This principle has been used to study the dispersions in the transition metal oxides CoO and Cu2O as well as in a proof-of-principle study, where copper was used as a test case.

CoO exhibits a magnetic phase transition at the Néel temperature, from a paramagnetic state into an antiferromagnetically ordered state. The presented data show a significant shift of spectral weight between different band structure regions as the sample temperature is elevated across the Néel temperature.

The Cu2O ARPES data have confirmed the existence of a hybridized Cu 3d - Cu 4s state. Through comparision with theoretically calculated results, a refined value of the Hubbard potential U has been determined.

An extensive ARPES dataset from copper, covering the entire Brillouin zone, has in a proof-of-principle study been used to derive the binding-energy resolved valence band charge density.

Two ARPES studies of the La2-x-yNdySrxCuO4 system have been performed in the cnventional low photon energy range. The high energy resolution has enabled a detailed study of dispersive features in the near Fermil level region of the valence band.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. x, 38 p.
Series
Trita-ICT/MAP, 2007:9
Keyword
angle-resolved photoelectron spectroscopy, electronic structure, oxides, high-temperature superconductors
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:kth:diva-4568 (URN)978-91-7178-783-5 (ISBN)
Public defence
2007-12-11, Sal N2, KTH-Electrum 3, Isafjordsgatan 28 A/D, Kista, 10:00
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Available from: 2007-12-07 Created: 2007-12-07 Last updated: 2010-07-02Bibliographically approved

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Tjernberg, Oscar

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