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Photoelectron Spectroscopy of High Temperature Superconductors and Related Compounds

Nylén, Henrik LU (1998)
Abstract
In this thesis, the high temperature superconductors (HTSC) Ba<sub>0.6</sub>K<sub>0.4</sub>BiO<sub>3</sub>, La<sub>2</sub>CuO<sub>4+x</sub>, Bi<sub>2</sub>Sr<sub>2</sub>Ca<sub>1-x</sub>Y<sub>x</sub>Cu<sub>2</sub>O<sub> 8+d</sub>, Bi<sub>2</sub>Sr<sub>2</sub>CuO<sub>6+d</sub> as well as semiconducting Ba<sub>0.9</sub>K<sub>0.1</sub>BiO<sub>3</sub> and the strongly magnetoresistant material La<sub>1-x</sub>Sr<sub>x</sub>MnO<sub>3</sub> have been studied by photoelectron spectroscopy. By using the... (More)
In this thesis, the high temperature superconductors (HTSC) Ba<sub>0.6</sub>K<sub>0.4</sub>BiO<sub>3</sub>, La<sub>2</sub>CuO<sub>4+x</sub>, Bi<sub>2</sub>Sr<sub>2</sub>Ca<sub>1-x</sub>Y<sub>x</sub>Cu<sub>2</sub>O<sub> 8+d</sub>, Bi<sub>2</sub>Sr<sub>2</sub>CuO<sub>6+d</sub> as well as semiconducting Ba<sub>0.9</sub>K<sub>0.1</sub>BiO<sub>3</sub> and the strongly magnetoresistant material La<sub>1-x</sub>Sr<sub>x</sub>MnO<sub>3</sub> have been studied by photoelectron spectroscopy. By using the tunability of synchrotron radiation, techniques such as resonant photoemission and x-ray absorption spectroscopy have been applied. The aim of the studies has been to investigate the electronic structure of these compounds with an emphasis on strong electron-electron correlation, the distribution of valence states, band structure effects, the importance of oxygen nonstoichiometry, and the influence of metal overlayers. Experimental results from the high quality single crystals are compared to band structure calculations and atomic absorption calculations.



Resonant photoemission was performed on Ba<sub>1-x</sub>K<sub>x</sub>BiO<sub>3</sub> at photon energies in the vicinity of the Ba 4<i>d</i>, Ba 5<i>p</i> and O 1<i>s</i> core levels. The enhancements seen in the valence band at photon energies corresponding to the Ba 5<i>p</i>-5<i>d</i> excitation are assigned to Ba states. From the resonance at the Ba 4<i>d</i> threshold, Ba states were also identified close to the Fermi level whereas no resonant enhancement was seen for photon energies close to the O <i>K</i> absorption threshold. In addition, angle resolved measurements were used to identify the G and X high symmetry points in Ba<sub>0.6</sub>K<sub>0.4</sub>BiO<sub>3</sub>, and laterally resolved photoelectron microscopy showed a strongly varying Fermi level intensity on a micron length scale.



For Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>8+d</sub> and Bi<sub>2</sub>Sr<sub>2</sub>CuO<sub>6+d</sub>, a satellite enhancement was seen for photon energies close to the main oxygen <i>K</i>-edge absorption threshold. From the data, the values of the electron-electron interaction energies <i>U<sub>dd</sub></i> and <i>U<sub>pp</sub></i>, as well as the charge transfer energy D, can be found. The core level shifts and the valence-band shape in cuprate HTSC were also investigated by means of yttrium substitution and surface derived electronic bands.



For La<sub>1-x</sub>Sr<sub>x</sub>MnO<sub>3</sub>, core-level spectroscopy and x-ray absorption measurements indicated that x and temperature dependent changes in the electronic structure can be connected to the various magnetic phases. Temperature dependent resonant photoemission at the O <i>K</i> and Mn <i>L</i><sub>3</sub> edges showed enhanced spectral intensity close to the Fermi level and for photon energies around the Mn <i>L</i> edge, strong enhancements were seen in the valence band.



The importance of small deviations in oxygen content is common for all compounds investigated in this thesis, although x-ray absorption and resonant photoemission measurements showed that O 2<i>p</i> holes play different roles in the doping mechanisms of cuprate and bismuthate high temperature superconductors as well as of magnetoresistant manganites. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Prof Grepstad, Jostein, Dept. of Physical Electronics, The Norwegian University of Science and Technology, NTNU, N-7034 Trondheim, Norway
organization
publishing date
type
Thesis
publication status
published
subject
keywords
egenskaper (elektriska, supraledare, magnetiska och optiska), magnetisk resonans, X-ray Absorption, Photoelectron Spectroscopy, Resonant Photoemission, Condensed matter:electronic structure, High Temperature Superconductors, Angle Resolved Photoemission, electrical, supraconductors, magnetic and optical properties, magnetic resonance, spectroscopy, spektroskopi, Kondenserade materiens egenskaper:elektronstruktur, relaxation, Fysicumarkivet A:1998:Nylén
pages
140 pages
publisher
Henrik Nylén, Dept. of Synchrotron Radiation Research, Box 118, S-221 00 Lund,
defense location
Lecture hall B, Institute of Physics, Lund
defense date
1998-05-28 10:15:00
external identifiers
  • other:ISRN: LUNFD6/NFSF--98/1013--SE
ISBN
91-628-2914-9
language
English
LU publication?
yes
additional info
Article: Paper I: Resonant photoemission study of Ba1-xKxBiO3 single crystalsH. Nylén, G. Chiaia, A. A. Zakharov, M. Qvarford, I. Lindau, V. G. Nazin, M. B. Tsetlin, M. N. Mikheeva, S. N. Barilo and S. V. ShiryaevPhys. Rev. B 56, 3467 Article: Paper II: Angle resolved photoemission study of Ba0.6K0.4BiO3 single crystalsH. Nylén, A. A. Zakharov, G. Chiaia, M. Leandersson, M. Qvarford, I. Lindau, M. B. Tsetlin, L. Lev, V. G. Nazin, M. N. Mikheeva, S. N. Barilo, and S. V. ShiryaevSubmitted for publication Article: Paper III: Metal-dielectric transition in Ba0.6K0.4BiO3-y single crystals studied by scanning photoelectron microscopyA. A. Zakharov, U. Johansson, M. Leandersson, H. Nylén, M. Qvarford, I. Lindau and R. NyholmPhys. Rev. B 56, R5755 (1997) Article: Paper IV: Core level photoemission and x-ray absorption study of oxygen deficient and Na covered Ba0.6K0.4BiO3 single crystalsH. Nylén, A. Beutler, A. A. Zakharov, M. Leandersson, M. Qvarford, I .Lindau, M. B. Tsetlin, L. Lev, M. N. Mikheeva, S. N. Barilo, and S. V. ShiryaevSubmitted for publication Article: Paper V: Valence band and resonance photoemission study of La2CuO4+x single crystalsA. A. Zakharov, H. Nylén, M. Qvarford, I. Lindau, M. Leandersson, M. B. Tsetlin, and M. N. MikheevaPhys. Rev. B. 56, 9030 (1997) Article: Paper VI: X-ray absorption study of oxygen in the high-Tc superconductor Bi2Sr2CaCu2O8 near the interfaces of Cu, Ag and AuM. Qvarford, S. Söderholm, O. Tjernberg, G. Chiaia, H. Nylén, R. Nyholm, I. Lindau, U. O. Karlsson and H. BernhoffPhysica C 265, 113 (1996) Article: Paper VII: Evidence of pseudogap related core level shifts in Bi2Sr2Ca1-xYxCu2O 8+d ,O. Tjernberg, H. Nylén, G. Chiaia, S. Söderholm, U. O. Karlsson, M. Qvarford, I. Lindau, C. Puglia, N. Mårtensson and L. LeonyukPhys. Rev. Lett. 79, 499 (1997) Article: Paper VIII: O KVV Auger emission versus resonant photoemission at the O K edge of high Tc-superconductorsH. Nylén, M. Qvarford, G. Chiaia, O. Tjernberg, S. Söderholm, A. A. Zakharov, M. Leandersson, V. G. Nazin, M. B. Tsetlin, L. Lev, J. N. Andersen, R. Nyholm, I. Lindau, U. O. Karlsson, M. N. Mikheeva, and L. LeonyukIn press Article: Paper IX: Temperature dependence in core level photemission on La1-xSrxMnO3 single crystalsH. Nylén, M. Leandersson, A. A. Zakharov, M. B. Tsetlin, L. Lev, M. N. Mikheeva, and I. LindauIn manuscript Article: Paper X: Temperature dependent resonant photoemission on La1-xSrxMnO3 single crystalsH. Nylén, M. Leandersson, A. A. Zakharov, M. B. Tsetlin, L. Lev, M. N. Mikheeva, and I. LindauIn manuscript
id
644e5164-c6f9-409b-8420-4f47df137004 (old id 38757)
date added to LUP
2016-04-04 10:17:51
date last changed
2018-11-21 20:57:59
@phdthesis{644e5164-c6f9-409b-8420-4f47df137004,
  abstract     = {In this thesis, the high temperature superconductors (HTSC) Ba&lt;sub&gt;0.6&lt;/sub&gt;K&lt;sub&gt;0.4&lt;/sub&gt;BiO&lt;sub&gt;3&lt;/sub&gt;, La&lt;sub&gt;2&lt;/sub&gt;CuO&lt;sub&gt;4+x&lt;/sub&gt;, Bi&lt;sub&gt;2&lt;/sub&gt;Sr&lt;sub&gt;2&lt;/sub&gt;Ca&lt;sub&gt;1-x&lt;/sub&gt;Y&lt;sub&gt;x&lt;/sub&gt;Cu&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt; 8+d&lt;/sub&gt;, Bi&lt;sub&gt;2&lt;/sub&gt;Sr&lt;sub&gt;2&lt;/sub&gt;CuO&lt;sub&gt;6+d&lt;/sub&gt; as well as semiconducting Ba&lt;sub&gt;0.9&lt;/sub&gt;K&lt;sub&gt;0.1&lt;/sub&gt;BiO&lt;sub&gt;3&lt;/sub&gt; and the strongly magnetoresistant material La&lt;sub&gt;1-x&lt;/sub&gt;Sr&lt;sub&gt;x&lt;/sub&gt;MnO&lt;sub&gt;3&lt;/sub&gt; have been studied by photoelectron spectroscopy. By using the tunability of synchrotron radiation, techniques such as resonant photoemission and x-ray absorption spectroscopy have been applied. The aim of the studies has been to investigate the electronic structure of these compounds with an emphasis on strong electron-electron correlation, the distribution of valence states, band structure effects, the importance of oxygen nonstoichiometry, and the influence of metal overlayers. Experimental results from the high quality single crystals are compared to band structure calculations and atomic absorption calculations.<br/><br>
<br/><br>
Resonant photoemission was performed on Ba&lt;sub&gt;1-x&lt;/sub&gt;K&lt;sub&gt;x&lt;/sub&gt;BiO&lt;sub&gt;3&lt;/sub&gt; at photon energies in the vicinity of the Ba 4&lt;i&gt;d&lt;/i&gt;, Ba 5&lt;i&gt;p&lt;/i&gt; and O 1&lt;i&gt;s&lt;/i&gt; core levels. The enhancements seen in the valence band at photon energies corresponding to the Ba 5&lt;i&gt;p&lt;/i&gt;-5&lt;i&gt;d&lt;/i&gt; excitation are assigned to Ba states. From the resonance at the Ba 4&lt;i&gt;d&lt;/i&gt; threshold, Ba states were also identified close to the Fermi level whereas no resonant enhancement was seen for photon energies close to the O &lt;i&gt;K&lt;/i&gt; absorption threshold. In addition, angle resolved measurements were used to identify the G and X high symmetry points in Ba&lt;sub&gt;0.6&lt;/sub&gt;K&lt;sub&gt;0.4&lt;/sub&gt;BiO&lt;sub&gt;3&lt;/sub&gt;, and laterally resolved photoelectron microscopy showed a strongly varying Fermi level intensity on a micron length scale.<br/><br>
<br/><br>
For Bi&lt;sub&gt;2&lt;/sub&gt;Sr&lt;sub&gt;2&lt;/sub&gt;CaCu&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;8+d&lt;/sub&gt; and Bi&lt;sub&gt;2&lt;/sub&gt;Sr&lt;sub&gt;2&lt;/sub&gt;CuO&lt;sub&gt;6+d&lt;/sub&gt;, a satellite enhancement was seen for photon energies close to the main oxygen &lt;i&gt;K&lt;/i&gt;-edge absorption threshold. From the data, the values of the electron-electron interaction energies &lt;i&gt;U&lt;sub&gt;dd&lt;/sub&gt;&lt;/i&gt; and &lt;i&gt;U&lt;sub&gt;pp&lt;/sub&gt;&lt;/i&gt;, as well as the charge transfer energy D, can be found. The core level shifts and the valence-band shape in cuprate HTSC were also investigated by means of yttrium substitution and surface derived electronic bands.<br/><br>
<br/><br>
For La&lt;sub&gt;1-x&lt;/sub&gt;Sr&lt;sub&gt;x&lt;/sub&gt;MnO&lt;sub&gt;3&lt;/sub&gt;, core-level spectroscopy and x-ray absorption measurements indicated that x and temperature dependent changes in the electronic structure can be connected to the various magnetic phases. Temperature dependent resonant photoemission at the O &lt;i&gt;K&lt;/i&gt; and Mn &lt;i&gt;L&lt;/i&gt;&lt;sub&gt;3&lt;/sub&gt; edges showed enhanced spectral intensity close to the Fermi level and for photon energies around the Mn &lt;i&gt;L&lt;/i&gt; edge, strong enhancements were seen in the valence band.<br/><br>
<br/><br>
The importance of small deviations in oxygen content is common for all compounds investigated in this thesis, although x-ray absorption and resonant photoemission measurements showed that O 2&lt;i&gt;p&lt;/i&gt; holes play different roles in the doping mechanisms of cuprate and bismuthate high temperature superconductors as well as of magnetoresistant manganites.},
  author       = {Nylén, Henrik},
  isbn         = {91-628-2914-9},
  language     = {eng},
  publisher    = {Henrik Nylén, Dept. of Synchrotron Radiation Research, Box 118, S-221 00 Lund,},
  school       = {Lund University},
  title        = {Photoelectron Spectroscopy of High Temperature Superconductors and Related Compounds},
  year         = {1998},
}