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On the lattice dynamical background of optical activity in crystals
Author(s) -
Claus R.
Publication year - 1979
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220960207
Subject(s) - polariton , physics , anharmonicity , dispersion relation , degenerate energy levels , condensed matter physics , lattice (music) , dispersion (optics) , phonon , scattering , optics , quantum mechanics , acoustics
The lattice dynamical theory of crystal optical activity developed by Born is discussed in the view of polariton dispersion. Three major difficulties occur: 1) For large wave vectors k no continuous connection with the phonon dispersion branches as recorded by neutron scattering is found. 2) There are spectral regions in which two left‐ or two right‐circularly polarized waves with different k are expected. 3) Polariton group velocities in the Γ‐point remain undefined when time reversal is required. An alternative model omitting these difficulties is proposed. It is based on the assumption of the existence of anharmonic resonance coupling between orthogonally polarized polariton waves with degenerate dispersion branches.