Original scientific paper
Acoustic collective excitations and static dielectric response in incommensurate crystals with real order parameter
V. Dananić
; Department of Physics, Faculty of Chemical Engineering and Technology, University of Zagreb, Maruli´cev trg 19, HR-10000 Zagreb, Croatia
A. Bjeliš
; Department of Theoretical Physics, Faculty of Science, University of Zagreb, Bijeniˇcka 32, HR-10000 Zagreb, Croatia
M. Latković
Abstract
Starting from the basic Landau model for the incommensurate-commensurate materials of the class I I, we derive the spectrum of collective modes for all (meta)stable states from the corresponding phase diagram. It is shown that all incommensurate states posses Goldstone modes with acoustic dispersions. The representation in terms of collective modes is also used in the calculation and discussion of static dielectric response for systems with the commensurate wave number in the center of the Brillouin zone.
Keywords
class I I incommensurate-commensurate materials; Landau model; spectrum of collective modes; Goldstone modes; dielectric response
Hrčak ID:
301052
URI
Publication date:
3.10.1999.
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