Anisotropy, phonon modes, and lattice anharmonicity from dielectric function tensor analysis of monoclinic cadmium tungstate

A. Mock, R. Korlacki, S. Knight, Mathias Schubert

Research output: Contribution to journalArticle

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Abstract

We determine the frequency dependence of four independent Cartesian tensor elements of the dielectric function for CdWO4 using generalized spectroscopic ellipsometry within mid-infrared and far-infrared spectral regions. Different single crystal cuts, (010) and (001), are investigated. From the spectral dependencies of the dielectric function tensor and its inverse we determine all long-wavelength active transverse and longitudinal optic phonon modes with Au and Bu symmetry as well as their eigenvectors within the monoclinic lattice. We thereby demonstrate that such information can be obtained completely without physical model line-shape analysis in materials with monoclinic symmetry. We then augment the effect of lattice anharmonicity onto our recently described dielectric function tensor model approach for materials with monoclinic and triclinic crystal symmetries [M. Schubert, Phys. Rev. B 93, 125209 (2016)2469-995010.1103/PhysRevB.93.125209], and we obtain an excellent match between all measured and modeled dielectric function tensor elements. All phonon mode frequency and broadening parameters are determined in our model approach. We also perform density functional theory phonon mode calculations, and we compare our results obtained from theory, from direct dielectric function tensor analysis, and from model line-shape analysis, and we find excellent agreement between all approaches. We also discuss and present static and above reststrahlen spectral range dielectric constants. Our data for CdWO4 are in excellent agreement with a recently proposed generalization of the Lyddane-Sachs-Teller relation for materials with low crystal symmetry [M. Schubert, Phys. Rev. Lett. 117, 215502 (2016)PRLTAO0031-900710.1103/PhysRevLett.117.215502].

Original languageEnglish (US)
Article number165202
JournalPhysical Review B
Volume95
Issue number16
DOIs
StatePublished - Apr 20 2017

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tensor analysis
tungstates
Cadmium
cadmium
Tensors
Anisotropy
anisotropy
tensors
Crystal symmetry
symmetry
line shape
Infrared radiation
Spectroscopic ellipsometry
Eigenvalues and eigenfunctions
ellipsometry
crystals
Density functional theory
Optics
eigenvectors
Permittivity

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Anisotropy, phonon modes, and lattice anharmonicity from dielectric function tensor analysis of monoclinic cadmium tungstate. / Mock, A.; Korlacki, R.; Knight, S.; Schubert, Mathias.

In: Physical Review B, Vol. 95, No. 16, 165202, 20.04.2017.

Research output: Contribution to journalArticle

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