Conduction plane temperature dependent

In this part we describe our experiments on studies of dissipation in Josephson flux-flow regime. We show that experiments of that type can be used for studies of temperature dependence of both the in-plane and the out-of-plane components of the quasiparticle conductivity [17]. 

Figure IV 2 10. Solid triangles show temperature dependence of the out-of-plane quasiparticle conductivity ac (a) and in-plane quasiparticle conductivity Gab (b). Below Tc they are extracted from the JFF experiment on BSCCO long stack [17] and above Tc they represent the normal state conductivities of whiskers measured independently on samples from the same batch. Open circles correspond to the oc data from Ref. 14, obtained on small mesas in zero field, open squares correspond to 14.4 GHz microwave data for cab from Ref. 18 obtained on epitaxial films. Solid lines in both plots are just guides for the eye. Insert in (a) shows the low temperature part of ac(T) plotted versus T2...

The most important result is that temperature dependence of the in-plane quasiparticle conductivity, heat transport measurements of the electronic part of the thermal conductivity [26],... 

Figure 4. The complex Cs[Pd(dmit)2]2- (a) temperature-dependent conductivity. [Adapted from (82).] (b) projection of the crystal structure onto the ac plane. [Drawn from the data available in (84).] (c) Projection of the crystal structure along the c axis. [Drawn from the data available in (84).]...

Suppose that one conducts a series of experiments to determine the stress and temperature dependence of creep behavior for the fibers and matrix these experiments would provide curves such as those shown schematically in Fig. 5.6a and b. Conducting these experiments over a range of temperatures and stresses would provide a family of curves that could be combined to provide a relationship between strain rate, stress, and temperature. Such a temperature and stress dependence of constituent intrinsic creep rates, together with the intrinsic creep mismatch ratio, is schematically illustrated in Fig. 5.6c. In this plot, the creep equations for the two constituents at a given temperature and stress are represented by planes in (1 IT, logo-, logs) space, with different slopes, described by <2/> Qm and ny, nm. The intersection of the two planes represents the condition where CMR = 1, which separates temperature and stress into two regimes CMR< 1 and CMR> 1. 

The origin for this apparent field dependence of rric is not fully understood. However, the nearly perfect two-dimensionality of -(ET)2l3 discussed in Sect. 2.3.3 seems to be the principal reason for the observed strange temperature and field dependence of the magnetic quantum oscillations. It was suggested that in this extremely 2D system quasiparticles with fractional statistics [365] may occur if the cyclotron orbits lie within an individual 2D conducting plane [363]. Since these quasiparticles do not obey Fermi statistics they should not contribute to the quantum oscillations observed. Hence, the effective cyclotron mass determined by the 3D Lifshitz-Kosevich formula could be underestimated. Further experimental verification for this suggestion is lacking. 

The brittle-ductile transition temperature depends on the characteristics of the sample such as thickness, surface defects, and the presence of flaws or notches. Increasing the thickness of the sample favors brittle fracture a typical example is polycarbonate at room temperature. The presence of surface defects (scratches) or the introduction of flaws and notches in the sample increases Tg. A polymer that displays ductile behavior at a particular temperature can break in the brittle mode if a notch is made in it examples are PVC and nylon. This type of behavior is explained by analyzing the distribution of stresses in the zone of the notch. When a sample is subjected to a uniaxial tension, a complex state of stresses is created at the tip of the notch and the yield stress brittle behavior known as notch brittleness. Brittle behavior is favored by sharp notches and thick samples where plane strain deformation prevails over plane stress deformation. 

The existence of a current hump near Tc is confirmed by several additional facts. In the first place, these are deduced from the results of the quantitative treatment of the impedance spectra of the HTSC/solid electrolyte system [147]. This approach consists of calculating from the experimental complex-plane impedance diagrams the parameters characterizing the solid electrolyte, the polarization resistance of the reaction with the participation of silver, and the double-layer capacitance (Cdi) for each rvalue (measured with an accuracy of up to 0.05°). Temperature dependence of the conductance and capacitance of the solid electrolyte (considered as control parameters) were found to be monotonic, while the similar dependences of two other parameters exhibited anomalies near Tc- The existence of a weakly pronounced minimum of Cji near Tc, which is of great interest in itself, was interpreted by the authors as the result of sharp reconstruction of the interface in the course of superconducting transition [145]. 

Critical current density also depends on magnetic field, decreasing monotonically to zero at the upper critical field Hc2 (16-17). In YBaCuO the slope of Hc2 with temperature is unusually large, of order 2 T/K when field is applied parallel to the predominant conduction planes of the structure (18-19). This implies record values (up to 200 T has been estimated) for the upper critical field at low temperatures and opens up the possibility of very high field magnets. 

Using these theoretical results for the quantities viVj) and Eqns. (8.74) and (8.75), a comparison with the experimentally determined temperature-dependent mobilities /Xy (see e.g. Fig. 8.35) yields the relaxation times r and the mean free path X as functions of the temperature. The results for holes in the naphthalene crystal are shown in Fig. 8.40. It follows that for T< 150 K, the conditions for the existence of band conductivity (Eqns. (8.64) and (8.65)) are well fulfilled in high-purity naphthalene crystals within the (a - h) plane. The same holds for other ul-... 

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