Neutron scattering studies of the electron-doped high-temperature superconductor neodymium cerium copper oxide
Abstract/Contents
- Abstract
- While the mechanism for the high transition temperatures (Tc) in the cuprate superconductors remains unsolved, antiferromagnetic fluctuations on the copper-oxygen sheets are thought to play an important role. Long-range antiferromagnetic order is present in the undoped insulating parent compounds, whereas superconductivity is observed when these materials are doped with a sufficient number of holes or electrons. Because these two phases are well separated on the hole-doped side of the phase diagram, the interplay between antiferromagnetism and superconductivity is perhaps better studied in the electron-doped compounds, where the two phases appear to overlap. In this Thesis work, single crystals of electron-doped Nd{2-x}Ce{x}CuO4 (NCCO) were grown over a wide range of cerium concentration, and the following two neutron scattering studies were performed on these crystals. In the first study, an energy-integrating neutron scattering method is used to measure the two-dimensional instantaneous magnetic correlation length as a function of temperature and doping. For x < 0.12, the correlation length diverges at the same temperature at which magnetic Bragg peaks appear, as expected. For x > 0.12, on the other hand, the correlation length remains finite down to the lowest measured temperatures. Since bulk superconductivity is only found above about x=0.13, this shows that there is no genuine coexistence between superconductivity and long-range antiferromagnetic order, which was previously thought to extend to x = 0.17. The second study is the first inelastic neutron scattering investigation of an electron-doped cuprate superconductor in an applied magnetic field. This experiment measures how the weakening of superconductivity due to a magnetic field affects the antiferromagnetic response. An advantage of the electron-doped cuprates is that the critical field Hc2 required to completely suppress superconductivity is relatively low (~10 T). In zero field, the antiferromagnetic excitation spectrum of NCCO (x=0.166) is gapped below 2.5 meV. The gap energy is found to decrease linearly with applied field and to extrapolate to zero near Hc2. The observed behavior indicates that the non-superconducting ground state is similar to the (zero-field) paramagnetic state at temperatures above Tc, and thus that superconductivity and antiferromagnetism are not competing orders in this part of the phase diagram.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Copyright date | 2010 |
| Publication date | 2009, c2010; 2009 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Motoyama, Eugene M |
|---|---|
| Associated with | Stanford University, Department of Physics |
| Primary advisor | Greven, Martin |
| Primary advisor | Kapitulnik, Aharon |
| Thesis advisor | Greven, Martin |
| Thesis advisor | Kapitulnik, Aharon |
| Thesis advisor | Kivelson, Steven |
| Advisor | Kivelson, Steven |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Eugene Makalu Davenport Motoyama. |
|---|---|
| Note | Submitted to the Department of Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2010. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2010 by Eugene M Motoyama
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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