Synchrotron X-ray scattering studies of anomalous oxygen order in superconducting mercury barium copper oxide and of charge-transfer excitations in related undoped lamellar copper oxides
Abstract/Contents
- Abstract
- The first part of this Thesis describes the discovery, using diffuse X-ray scattering, of an unconventional interstitial-oxygen chain order in the model cuprate superconductor HgBa2CuO4+d. The oxygen order occurs within the Hg-O plane and the typical chain length is found to be about 25 unit cells. This order is unconventional, because of the observed high ordering temperature (around 800 K), the temperature-independent chain length, the weak associated lattice distortions, and the conservation of the global tetragonal symmetry of the crystal lattice. Moreover, the chains are observed only above a critical oxygen concentration, which coincides with the disappearance of a recently discovered novel magnetic order and the with the plateau anomaly on the underdoped side of the superconducting dome. One possible interpretation of the findings is that the appearance of the oxygen order is a manifestation of an underlying change in the electronic structure of the copper-oxygen planes. The second part of this Thesis describes experimental and theoretical Cu K-edge resonant inelastic X-ray scattering (RIXS) results for the charge-transfer excitations of several related undoped Mott insulators. First, in a study of Nd2CuO4, scattered-photon polarization effects are observed in the inelastic spectrum at the Brillouin-zone center. Raman selection rules accurately model these effects, which suggests that non-A1g charge-transfer excitations can be observed with RIXS. Next, the 1s4p electron-hole pair Coulomb scattering potential responsible for RIXS excitations at the Cu K-edge is calculated. While the strongest interaction is local and isotropic, non-local and anisotropic interactions are found to be sizable, and the formula for these Coulomb interactions is shown to follow selection rules which agree well with the observed scattered-photon polarization effects. In a separate experimental investigation, the momentum-dependent intensity of charge-transfer excitations of undoped cuprates is measured with RIXS, at the Cu K-edge. Reciprocal-space maps of the RIXS intensity at fixed energy show that the observed inelastic features are intrinsically broad and centered about high-symmetry points. Moreover, dispersion diagrams (constructed from energy scans collected along high-symmetry directions) show that these features correspond to distinct weakly-dispersing branches. Finally, a comparison of these branches for the compounds La2CuO4, Nd2CuO4, and Sr2CuO2Cl2 shows that the excitations constitute a universal set of features of the strongly-correlated electronic structure of the common copper-oxygen plane.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2010 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Chabot-Couture, Guillaume |
|---|---|
| Associated with | Stanford University, Department of Applied Physics |
| Primary advisor | Doniach, S |
| Primary advisor | Greven, Martin |
| Thesis advisor | Doniach, S |
| Thesis advisor | Greven, Martin |
| Thesis advisor | Devereaux, Thomas Peter, 1964- |
| Thesis advisor | Fisher, Ian R. (Ian Randal) |
| Advisor | Devereaux, Thomas Peter, 1964- |
| Advisor | Fisher, Ian R. (Ian Randal) |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Guillaume Chabot-Couture. |
|---|---|
| Note | Submitted to the Department of Applied Physics. |
| Thesis | Thesis (Ph. D.)--Stanford University, 2010. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2010 by Guillaume Chabot-Couture
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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