Biphonon transverse

Macroscopic theory - Transverse, longitudinal, and surface biphonons... 

FlG. 6.8. Dependence of the dielectric function on the frequency in the region of overtone frequencies E b and E b are the energies of the longitudinal and transverse biphonons, respectively m n and emax are the minimum and maximum energy values in the band of two-particle states. 

In the region of longitudinal-transverse splitting 0yb < u> < Op, where e(u>) < 0, surface biphonons should also exist. At the boundary with the vacuum, their dispersion law satisfies the relation... 

FlG. 6.11. Polariton dispersion in the NH4CI crystal. Longitudinal-transverse splitting of the biphonon is observed in the frequency region v 1460 cm-1 (from (61)). 

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