Transverse conductivity

One of the surprising results of the early pressure studies is shown in Fig. 10 [27]. In the range investigated, both transverse components of the conductivity increased with pressure at the same rate as important factors in the development of Weger s theory of the transverse conductivity of anisotropic metals [75]. In this... 

Knowledge of the pressure-induced commensurability led to a series of beautiful experiments searching for evidence for a collective electron-phonon or CDW contribution to the low field conductivity in TTF-TCNQ above Tp. Clear evidence was indeed found for a substantial fall in ah between about 150 and 80 K in the narrow commensurability domain, as shown in Fig. 14 [85]. No such dip was found for the transverse conductivity [86], and the dips in ah were also shown to be suppressed by only a 2 x 10 3 molecular fraction of irradiation induced defects [87]. All of this leads to a consistent picture in favor of a collective electron-phonon CDW contribution to ah above Tp of TTF-TCNQ, as discussed in Ref. 2. However, the extra CDW conductivity is not more than 6000 (fl-cm)-1 at 80 K, that is, about one-half of the ambient pressure conductivity of (TMTSF)2PF6 at the same temperature (Fig. 1) and the latter is usually considered to be a single-particle contribution. So until the mechanism... 

The resistivity anisotropy of the TM2X series is typically 1 200 30,000 along the a, b, and c axes, respectively, leading to the overlap anisotropy ta tb tc = 10 1 0.1 with the assumption of incoherent transverse conduction... 

The longitudinal thermal conductivity of solid wood is approximately 2.5 times higher than the transverse conductivity [45] ... 

The inter-chain hopping of electrons observed by the NMR experiment could be the same mechanism for the transverse conductivity. Assuming the diffusive mechanism for the transverse conductivity, qj., Cj. is given by... 

TTF-TCNQ and TTF-TCIMQC04). The pressure variation of the norma lized transverse conductivity a (P)/c (1 atm) is also shown. 

The cut-off frequency has been found strongly pressure dependent /6/ and the large increase observed at low temperature /32/ is correlated with the low temperature increase of the transverse conductivity /23, 33/. The transverse motion progressively changes from a diffusive model at high temperature to a coherent model at low temperature. A detailed experimental analysis of the Id to 3d change occurring in the electronic properties as a function of the temperature has been performed in HQ /2 5/. 

Defining the longitudinal and transversal conductivities from relation ... 

Thus, in the quasistationary approximation for the considered model of a medium, the dependence of conductivity on frequency is absent, and consequently, expressions for transversal conductivity and coefficient of anisotropy have the form ... 

An arbitrary oriented magnetic dipole can be presented as a sum of two dipoles, namely, a vertical and a horizontal one. In excitation of the field by a vertical magnetic dipole, induced currents are located in horizontal planes and do not depend on the transversal conductivity cr . 

Thus, at the range of small parameters, L/h, the quadrature component of the field is directly proportional to the transversal conductivity [Pg.613]

When the electric field is applied perpendicular to the fiber direction, a suspension of fibers is similar to the suspension of cells described above (in Figure 21. la, we must now imagine that the circles represent cross sections of cylindrical fibers, rather than spherical cells). The expression for the effective transverse conductivity of a suspension of cylindrical cells, of radius a and intracellular conductivity cr , placed in a solution of conductivity a, with intracellular volume fraction/, is [Cole, 1968]... 

In the second model, each filament carried the same fraction I/Ic of its critical current, and for this case hystersis loss depends upon I and higher powers of I/Ic. Whether or not an interfacial resistance exists at the filaments may be determined from the transverse conductivity, (7j, of the composite. An approximate expression for this conductivity, in the absence of interfacial resistance, is [ ]... 

Hall coefficient, for nearly free transverse conductivity... 

Very recently, Harris (1986) has employed the Kubo-Greenwood formalism and weak-scattering theory to evaluate the transverse conductivity in a magnetic field, and hence He finds... 

He thus conclude that the effect of different velocities In adjacent channels is not great. This conclusion was reached, however, for a model which excludes axial conduction of heat. However, we have made calculations for three different types of transverse conduction different geometries of the duct (7 ), peripheral conduction around the duct (5), and now different velocities in adjacent ducts. In the first two cases the Inclusion or exclusion of axial conduction had little effect on the qualitative conclusion as to the importance of the effect, and there is no reason to assume that the multiple channel analysis will be any different. The inclusion of axial conduction will have a dramatic effect on the hysteresis but that hysteresis should not be greatly affected by any of the three transverse phenomena different geometries, peripherlcal conduction, or multiple channels with different velocities. We thus conclude that analyzing a single channel suffices. 

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