Zero-frequency conductivity, temperature

Fig. 8. Temperature dependence of the zero-frequency conductivity of the paired holon superconductor. The curve is indistinguishable for the three coupling strengths X 0.1, X= 0.5 and X= 1.2.

Ionic conduction has been shown to occur in MHFg (M = K, Rb, or Cs) in both the a (tetragonal) and the / (cubic) phases. Plots of the zero-frequency conductivities versus T show discontinuities at the a-/S transition temperatures moreover, the gradients for the phases are all essentially the same (A 20 kcal), whereas there are considerable differences between the... 

Fig. 21. Real part of the conductivity of YbFe4St>i2- The symbols on die left axis represent dc values at different temperatures. Below T (fv 50 K), a narrow peak at zero frequency and a gap-like feature at 18 meV gradually develop. Inset Renormalized band structure calculated from die Anderson lattice Hamiltonian. % and f denote bands of free carriers and localized electrons, respectively. At low temperatures a direct gap A opens. The Fermi level, Ep is near die top of die lower band,, resulting in hole-like character and enhanced effective mass of die quasiparticles (Dordevic et al., 2001).

The Brillouin linewidth Td) depends on the dynamic shear and volume viscosities r s(w) and t v(w). If the hypersonic shear viscosity r s(Aa)(i)) is equal to the zero frequency shear viscosity and the small term caused by thermal conductivity is neglected, then measurements of Td) can be used to obtain the volume viscosity. Champion and Jackson (8) noticed that the volume viscosities determined in the above manner for the n-alkanes were essentially independent of temperature. The values of r(i) measured in the authors laboratory for n-hexadecane are plotted... 

Most studies of the electrical properties of HMFG report conductivity versus temperature measurements, either DC (see, e.g. Almeida and Mackenzie 1982) or AC with use of complex impedance plots extrapolated to zero frequency (see, e.g. Ravaine 1985). Arrhenius behavior was always observed for the electrical conductivity cr below Tg... 

Conductive-system dispersion (CSD) usually involves thermally activated conduction extending to zero frequency plus an always-present bulk dielectric constant, usually taken to be frequency-independent in the experimental range. Dielectric-system dispersion (DSD) often involves dielectric-level response with only weak temperature dependence, and it may or may not involve a non-negligible frequency-independent leakage resistivity, pc = Pdc = po= 1/ob- There may be cases where separate processes lead to the simultaneous presence within an experimental frequency range of both types of dispersion, but this is rare for most solid electrolytes. Further complications are present when conduction involves both mobile ionic and electronic charges, neither of whose effects are negligible (Jamnik [2003]). Here only ionic, dipolar, and vibronic effects will be further considered, with the main emphasis on conductive rather than on dielectric dispersion. 

Recent work by the Heeger group [196] on P(Py)/PF6, using a Kramers-Kronig transformation of IR Reflectance data to obtain conductivities and extinction coefficients at IR frequencies has shown up an interesting property of this material Nearly all the ambient temperature DC conductivity of this polymer appears from a narrow conductivity peak (Fig. 6-181 near zero frequency, and there appears to be... 

Figure 21 shows results for the frequency dependence of the ac conductivity, for E1.5B1H at several temperatures. As expected, and obtained by extrapolation to zero frequency, increase with increasing temperature. However, a discontinuity is observed in the spectra with a large step between 303 and... 

We consider a disordered system of point localization centers. The general expression for the low-frequency resonance AC conductivity in the pair approximation at zero temperature is [2]... 

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