Phonon modes of MgB2 : Super-lattice structures and spectral response
Alarco, Jose A., Chou, Alison, Talbot, Peter Cade, & Mackinnon, Ian D.R. (2014) Phonon modes of MgB2 : Super-lattice structures and spectral response. Physical Chemistry Chemical Physics, 16, pp. 24443-24456.
Micrometre-sized MgB2 crystals of varying quality, synthesized at low temperature and autogeneous pressure, are compared using a combination of Raman and Infra-Red (IR) spectroscopy. These data, which include new peak positions in both spectroscopies for high quality MgB2, are interpreted using DFT calculations on phonon behaviour for symmetry-related structures. Raman and IR activity additional to that predicted by point group analyses of the P6/mmm symmetry are detected. These additional peaks, as well as the overall shapes of calculated phonon dispersion (PD) models are explained by assuming a double super-lattice, consistent with a lower symmetry structure for MgB2. A 2x super-lattice in the c-direction allows a simple correlation of the pair breaking energy and the superconducting gap by activation of corresponding acoustic frequencies. A consistent physical interpretation of these spectra is obtained when the position of a phonon anomaly defines a super-lattice modulation in the a-b plane.
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|Item Type:||Journal Article|
|Keywords:||MgB2, Phonon disperson, Phonon density of states, Raman spectroscopy, superconductivity|
|Subjects:||Australian and New Zealand Standard Research Classification > PHYSICAL SCIENCES (020000) > CONDENSED MATTER PHYSICS (020400) > Condensed Matter Modelling and Density Functional Theory (020403)
Australian and New Zealand Standard Research Classification > PHYSICAL SCIENCES (020000) > CONDENSED MATTER PHYSICS (020400) > Electronic and Magnetic Properties of Condensed Matter; Superconductivity (020404)
Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > ANALYTICAL CHEMISTRY (030100) > Analytical Spectrometry (030101)
|Divisions:||Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > Institutes > Institute for Future Environments
Current > QUT Faculties and Divisions > Science & Engineering Faculty
|Copyright Owner:||Copyright 2014 the Owner Societies|
|Copyright Statement:||Open Access Creative Commons Attribution Non-commercial 3.0|
|Deposited On:||19 Oct 2014 22:24|
|Last Modified:||21 Oct 2014 21:55|
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