Effects of disorder

In this contribution, we discussed effects of disorder on the electronic properties of quasi-one-dimensional Peierls systems, like the conjugated polymer fraus-poly-acetylene. Since polymer materials generally are rather disordered and the effect of disorder on any quasi-one-dimensional system is strong, a proper description of these materials requires consideration of such effects. 

This model, which is sometimes referred to as the Fluctuating Gap Model (FGM) [42], has been used to study various aspects of quasi-one-dimensional systems. Examples arc the thermodynamic properties of quasi-one-dimensional organic compounds (NMP-TCNQ, TTF-TCNQ) [271, the effect of disorder on the Peierls transition [43, 44, and the effect of quantum lattice fluctuations on the optical spectrum of Peierls materials [41, 45, 46]. 

Thus, all above experimental examples indicate that additionally to effect of disordering of the surface of adsorbent on its adsorption characteristics it is necessary to account for the effect of the adsorption itself on degree of adsorbent disordering controlling both its own electrophysical characteristics and the adsorption-caused change while deriving the theory of adsorption response of polycrystalline semiconductor adsorbent. 

In order to study the effect of disorder between two atoms, single crystals composed of pairs of the complexes [TpBut]ZnCl, [TpBut]ZnI, and [TpBut]ZnMe, over a range of compositions, were studied. In each case, only a single atom was observed at the disordered site, and the Zn-X bond length that was measured corresponded to a composite for the... 

Depression is not just an individual problem it is also a social problem. The people most likely to become depressed are poor, unemployed and undereducated.53 To some extent, this may be due to what is called social selection or economic drift. People who are chronically depressed might find it harder to perform well or even hold a job, and this might lead to a downward shift in their economic status. But there are data showing that the cause and effect can also run in the opposite direction.54 Different ethnic groups, for example, have different rates of depression. As the authors of one of the studies investigating this pointed out, ethnic status cannot be an effect of disorder because it is present at birth . Another study showed that people are more likely to become depressed if their parents were poor or less educated. These data cannot be explained by the economic-drift hypothesis. In other words, poverty and discrimination can cause depression. 

H). As shown, a disordered structural model was obtained for the guest. The model comprises two mirror-related guest molecules. The oxygen atom and the proximal methyl C-atom are practically overlapping the same atomic positions in both orientations. However, the sulphur atomic positions do not average in the X-ray data and show a nearly 50/50 occupancy. As indicated by the comparison of the respective bond distances and intra-associate contact distances of the DMSO molecule (Table 17), the effect of disorder is serious (e.g. the S=0 distances appear abnormally short in the 20 DMSO instance). This precludes the possibility of assessing interaction between the O atom of the carboxyl and a methyl of dimethyl sulfoxide. 

In addition, many of the ferroelectric solids are mixed ions systems, or alloys, for which local disorder influences the properties. The effect of disorder is most pronounced in the relaxor ferroelectrics, which show glassy ferroelectric behavior with diffuse phase transition [1]. In this chapter we focus on the effect of local disorder on the ferroelectric solids including the relaxor ferroelectrics. As the means of studying the local structure and dynamics we rely mainly on neutron scattering methods coupled with the real-space pair-density function (PDF) analysis. 

Volume 45 Effect of Disorder and Defects in Ion-Implanted Semiconductors Electrical and Physiochemical Characterization... 

LEED theory for disordered surfaces (effects of disorder in the surface structure are added to a full dynamical theory). 

A more recent review of the properties of this material has been given by von Molnar and Penney (1985 see also von Molnar et al 1983, 1985). Results discussed in this article, involving the effects of disorder and electron-electron interaction, are described in Chapters 5 and 9. Briefly, the semiconductor-to-metal transition in an increasing magnetic field leads to a conductivity, at 300 mK, that increases linearly with H (von Molnar et al 1983). This is shown in Fig. 3.7. Hopping conduction is observed with an index indicating the influence of a Coulomb gap (Washburn et al 1984), and near the transition a temperature dependence of a as a+mT, with m positive (von Molnar et al 1985). 

Another important issue requiring further studies is the role of carrier-carrier correlation. It is known that the effect of disorder on carrier-carrier interactions controls the localization and enhances the spin susceptibility (Altshuler and Aronov 1985), and thus the tendency towards ferromagnetism. However, spin-disorder scattering may limit the efficiency of this process (Altshuler and Aronov 1985). If this is the case, LSDA (Jungwirth et al. 1999 Lee et al. 2000) can provide a reasonable evaluation of the relevant Fermi-liquid parameter. 

It is worth pointing out that, even without the effects of disorder, there will be a fairly rapid, though not monotonic, decrease of intensity with progressively higher order of diffraction maxima except in the artificial case of point atoms. The extreme case of this effect is illustrated by the argument associated with Equations (2.10) and (2.11). 

The influence of a commensurate lattice potential on a free density wave is considered in section 5. The full finite temperature renormalization group flow equation for this sine-Gordon type model are derived and resulting phase diagram is discussed. Furthermore a qualitative picture of the combined effect of disorder and a commensurate lattice potential at zero temperature is presented in section 6, including the phase diagram. 

The combined effect of disorder and the lattice potential on the zero temperature phase diagram, i.e., the competition between unpinning (Anderson) and lock-in (Mott) transition, is still controversially discussed [41, 14] and cannot be explained by the RG-results presented here, since both perturbations become relevant for small K. However, using Imry-Ma arguments one finds, that as soon as If is below one of the two critical values (for the unpinning and lock-in transition) the disorder dominates the lattice potential and only two phases exist. This is in contrast to the proposed existence of a so-called intermediate Mott- Glass phase [14]. 

In conclusion, we mention that the effects of disorder on the kinetics of quasiparticles confined in an insulator/normal-metal/superconductor (INS) hybrid structure due to Andreev reflections was first considered in Ref. [12] within a model where the disorder is provided by irregularities on the I/N boundary through the normal scattering of quasiparticles. 

This suggests that to first order the effect of disorder induced localization can be introduced into a reduced model for DNA by sampling the couplings from a normal distribution about the average B-DNA coupling. However, this may introduce too severe of an approximation when it comes to dynamics and transport related properties that may be sensitive to dynamical correlations amongst the coupling terms. 

In relation to these solid-state measurements, a detailed study,195 both empirical and theoretical, of the effect of disorder on the electronic excited states of a hexa(alkylthio)triphenylene 20 (R = S-alkyl) in the bulk state has been conducted. Small but measurable shifts in the absorption maximum are seen... 

The effect of disorder in the water structure on the correlation length Xm. 114... 

EFFECTS OF DISORDER WITH FINITE RANGE ON THE PROPERTIES OF D-WAVE SUPERCONDUCTORS... 

Effects of Disorder with Finite Range on the Properties of d-Wave... 

---