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Quantum saturation of the order parameter and the dynamical soft mode in quartz

2003; IOP Publishing; Volume: 15; Issue: 2 Linguagem: Inglês

10.1088/0953-8984/15/2/331

1361-648X

Francisco Javier Romero, Ekhard K. H. Salje,

High-pressure geophysics and materials

The temperature evolution of the static order parameter of α-quartz and its soft-mode frequencies were determined at temperatures below 300 K. While these parameters follow classic Landau theory at higher temperatures, quantum saturation was found below room temperature with a characteristic quantum temperature of 187 K. A quantitative analysis gave a good agreement with the predictions of a Φ6 model close to the displacive limit and a rather flat dispersion of the soft-mode branch. No indication of any effect of strong mode–mode coupling on the saturation behaviour was observed.