It is well known that the optical branches of the dispersion curves of ionic crystals exhibit a polaritonic feature, i.e., a splitting about the electromagnetic dispersion line ω = ck. This phenomenon is considered to be due to the retardation of the electromagnetic forces among the ions. However, the problem is usually discussed at a phenomenological level, through the introduction of a macroscopic polarization, so that a microscopic treatment is apparently lacking. A microscopic first principles deduction is given here, in a classical frame, for a model in which the ions are dealt with as point charges. At a qualitative level it is made apparent that retardation is indeed responsible for the splitting. A quantitative comparison with the empirical data for LiF is also given, showing a fairly good agreement over the whole Brillouin zone.

Classical microscopic theory of polaritons in ionic crystals / A. Lerose, A. Sanzeni, A. Carati, L. Galgani. - In: THE EUROPEAN PHYSICAL JOURNAL. D, ATOMIC, MOLECULAR AND OPTICAL PHYSICS. - ISSN 1434-6060. - 68:2(2014 Feb). [10.1140/epjd/e2013-40331-y]

Classical microscopic theory of polaritons in ionic crystals

A. Sanzeni
Secondo
;
A. Carati
Penultimo
;
L. Galgani
Ultimo
2014

Abstract

It is well known that the optical branches of the dispersion curves of ionic crystals exhibit a polaritonic feature, i.e., a splitting about the electromagnetic dispersion line ω = ck. This phenomenon is considered to be due to the retardation of the electromagnetic forces among the ions. However, the problem is usually discussed at a phenomenological level, through the introduction of a macroscopic polarization, so that a microscopic treatment is apparently lacking. A microscopic first principles deduction is given here, in a classical frame, for a model in which the ions are dealt with as point charges. At a qualitative level it is made apparent that retardation is indeed responsible for the splitting. A quantitative comparison with the empirical data for LiF is also given, showing a fairly good agreement over the whole Brillouin zone.
Polaritons ; dispersion curves ; ionic crystals
Settore MAT/07 - Fisica Matematica
Settore FIS/02 - Fisica Teorica, Modelli e Metodi Matematici
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/232702
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