DEPHASING RATE IN DIELECTRIC GLASSES AT ULTRALOW TEMPERATURES

A novel mechanism for dephasing in dielectric glasses is considered. T he mechanism is due to the delocalized collective excitations arising in the ensemble of the interacting two-level systems. The spectral dif fusion induced by these excitations gives rise to the phonon-independe nt transverse relaxation. The mechanism results in the linear temperat ure dependence of the dephasing rate and becomes predominant at ultral ow temperatures. A qualitative agreement with the experimental data is found.