Disorder-induced far infrared absorption in amorphous materials

Terahertz time-domain spectroscopy: A new tool for the study of glasses in the far infrared

“…(3) indeed provides a very good model for the data. The values of parameters b and K 0 obtained from the fit to the silica data agree with those quoted by Strom et al [12,13]. In particular, the exponent is b = 2, which is the expected value for covalent glasses such as silica.…”

“…This procedure gave a set of 10 results which were averaged to reduce the error. The averaged absorption [12][13][14][15] explains far-infrared absorption in amorphous materials in terms of disorder-induced coupling of radiation into the acoustic phonon modes of the material. The model applies at frequencies such that 2pm ) V D /l, where V D is the Debye velocity of sound and l is the average correlation length in the material; and states that the frequencydependent absorption coefficient a(m) can be describes by the power-law relation…”

First and Second Universalities: Expeditions Towards and Beyond

“…Figure 5 shows the example of a silver thiogermanate glass [39,40]. In this log-log representation of the total (ionic) conductivity, σ (ν), the contribution due to vibrations is seen to have a slope of two on its low-frequency flank, which is known to be the usual behaviour in ionic solids [41]. This component, σ vib (ν), can be carefully removed from the experimental spectrum.…”

Terahertz response of organic amorphous systems: experimental concerns and perspectives

“…In inorganic glasses, the temperature effect on the VDOS is usually negligible [21], but this is not the case for organic glasses. An example can be seen in Figure 6, where standard THz-TDS results have been extended to higher frequencies by a combination of the TDS data with those obtained using the far-infrared beamline B22 at the Diamond Light Source following Kramers-Kronig analysis for a sample of amorphous sorbitol [22].…”

“…The far-infrared absorption of glasses often follows α(ν) ∝ ν 2 [21], which can be explained by the approximation g(ν) ≈ g Debye (ν) and C(ν) ≈ A. Considering the latter to hold, it is possible to determine the excess to the Debye VDOS by examining α(ν)/ν 2 .…”