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The importance of high temperature electron-phonon coupling to the thermodynamic properties of Ce0.9Th0.1 and other f-electron bonded metals
- M. E. Manley, R. J. McQueeney, B. Fultz, T. Swan-Wood, O. Delaire, E. A. Goremychkin, J. C. Cooley, W. L. Hults, J. C. Lashley, R. Osborn, J. L. Smith
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- Journal:
- MRS Online Proceedings Library Archive / Volume 802 / 2003
- Published online by Cambridge University Press:
- 01 February 2011, DD2.3
- Print publication:
- 2003
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- Article
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Recent results from inelastic neutron scattering studies on Ce0.9Th0.1 are used to demonstrate the importance of electron-phonon coupling to the physical properties of f-electron bonded metals. In the case of Ce0.9Th0.1, the phonon density of states (DOS) of α-phase shows a significant softening when heated but shows no change across the α-γ transition despite the 11% volume change. This is supported by analysis of the magnetic spectra showing that most of the transition entropy can be accounted for with the crystal field and spin fluctuations. The precursor phonon softening, the lack of any phonon change across the transition, the magnetic spectra, and the volume transition itself can all be explained in terms of the atomic displacement sensitivity of the hybridization of the local f-electrons with conduction electrons. The electron-phonon coupling resulting from these displacement-sensitive electronic states appears to be essential to understanding cerium. Some of the behavior characteristic of these states, a large volume changes and precursor phonon softening, occurs in many other f-electron bonded metals suggesting that the phenomena is not unique to cerium.
10 - Experimental evidence of local lattice distortion in superconducting oxides
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- By T. Egami, Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104-6272, USA; Department of Materials Science and Engineering, W. Dmowski, Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104-6272, USA; Department of Materials Science and Engineering, R. J. McQueeney, Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104-6272, USA; Department of Materials Science and Engineering, T. R. Sendyka, Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104-6272, USA; Department of Physics, S. Ishihara, Institute for Materials Research, Tohoku University, Sendai 980, Japan, M. Tachiki, Institute for Materials Research, Tohoku University, Sendai 980, Japan, H. Yamauchi, International Superconductivity Technology Center, Superconductivity Research Laboratory, Tokyo 135, Japan, S. Tanaka, International Superconductivity Technology Center, Superconductivity Research Laboratory, Tokyo 135, Japan, T. Hinatsu, Department of Applied Physics, University of Tokyo, Tokyo 103, Japan, S. Uchida, Department of Applied Physics, University of Tokyo, Tokyo 103, Japan
- Edited by E. K. H. Salje, University of Cambridge, A. S. Alexandrov, University of Cambridge, W. Y. Liang, University of Cambridge
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- Book:
- Polarons and Bipolarons in High-Tc Superconductors and Related Materials
- Published online:
- 24 November 2009
- Print publication:
- 07 September 1995, pp 155-179
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Summary
Abstract
If lattice polarons exist in high-temperature superconducting oxides then there must be evidence of local lattice distortion associated with polarons. While the distortions are dynamic and subtle, making direct observation difficult, there are numerous indications that some anomalous local deviations from the crystallographic lattice structure exist in superconducting oxides. Based largely upon the results of pulsed neutron scattering measurements, we present an argument in favor of the presence of local lattice distortions consistent with lattice polarons. A few implications of the observation in relation to other physical properties are discussed.
Introduction
Even though polarons have been known for a long time, direct experimental observation of lattice distortions associated with them is surprisingly scarce, largely because the density of polarons is usually low and consequently the lattice distortion is small on average, making observation very difficult. While some observations of lattice distortion associated with polarons have been made for low-dimensional organic conductors in which the periodic lattice distortion (Peierls distortion) can be regarded as an array of localized polarons [1], there are very few such reports for oxides [2]. Moreover, most known cases of polarons are heavy, small polarons, while in high-temperature superconducting (HTSC) oxides the presence of mobile large polarons is suspected. For those reasons, local lattice distortion has been observed so far mostly by nontraditional methods of structural study, while the crystallographic community has largely been skeptical. In this paper we discuss why observation is difficult, whether there is sufficient experimental evidence to support the presence of polarons in high-temperature superconducting oxides or not, and the implications of these observations.