Strong-correlation fluctuations

Both the room-temperature thermoelectric power and the phonon-drag component at low temperatures increase with hydrostatic pressure due to a decrease in the volume fraction of strong-correlation fluctuations in an itinerant-electron matrix. 

Where strong-correlation fluctuations are present in an itinerant-electron matrix, the magnetic susceptibility may be interpreted as a coexistence of Curie-Weiss and mass-enhanced Pauli paramagnetism. 

A semidilute solution is characterized by the large and strongly correlated fluctuations in the segment density such as we have in dilute solutions. Although the fluctuations decrease with increased polymer concentration, the semidilute solution still retains the same character as critical phenomena in statistical mechanics, and presents the same kind of problem as we discussed in Sections 2.5 and 2.6. ... 

An extension of fluorescence correlation spectroscopy is to measure the cross-correlation of fluorescence from two different fluorophores, such as a ligand and its receptors [272]. Strongly correlated fluctuations of the fluorescence from a small volume element indicate that the two species diffuse into and out of the element together, as would be expected for a complex. This approach has been used to study renaturation of complementary strands of nucleic acids [273], enzymatic fusion and... 

I = insulator, s.c. = semiconductor, cond. = conductor, AF = antiferromagnetic, F = ferromag-net, scf = strong-correlation fluctuations, J-T = cooperative Jahn-Teller orbital ordering, LS = J-T that maximizes orbital angular momentum, dis. = disproportionation 2(j = e + e, SDW/ CDW = spin/charge-density wave. 

Three features of Fig. 15a are noteworthy (i) the p(T) curves, which are similar at ambient pressure to those reported by others [80, 81], have a temperature dependence typical for a Fermi liquid however, they are too high and pressure-sensitive for a conventional metal with a mean-free path of more than one lattice parameter (ii) the low-temperature phonon-drag enhancement, which has a maximum at T ax 70 K in the oxide perovskites, is largely suppressed but it is partially restored by pressure (iii) a d a(300 K) / dP > 0 (a is enhanced by 15% in 14 kbar pressure) indicates an anomalous increase in m with pressure. Features (ii) and (iii) were also found in CaV03 where they were shown (see Sect 1.2.1) to be a signature for the existence of strong-correlation fluctuations in a Fermi liquid. The features (i) and (iii) are also present in the metallic phase of the orthorhombic samples, see Fig. 15b, c ... 

Significantly, the (T) curve for Ndo.5Smo.5Ni03, Fig. 18d, shows no anomaly at Tt as defined by p(T). This observation demonstrates that the CDW below a Tt > Tn is not stabilized by either Fermi-surface nesting or the onset of a homogeneous Mott-Hubbard transition. However, it is compatible with an order-disorder transition for strong-correlation fluctuations. 

The enhancement of x(T) in the metallic phase exhibits temperature and bandwidth dependencies that are not described by existing models of homogeneous electronic systems, but they are consistent with a heterogeneous model of strong-correlation fluctuations in a mass-enhanced matrix as deduced from our transport measurements. 

The lack of any change in x(T) on traversing the insulator-metal transition at T, > Tn is incompatible with a homogeneous model of Fermi-surface nesting or a Mott-Hubbard transition, but it can be understood as an order-disorder transition of preexisting strong-correlation fluctuations. 

Finally, Ghosh et al. [88] have reported low-energy excitations in LaNiOs that require the existence of two conditions (i) a collection of two-level systems with a broad distribution and (ii) a flat density of states at low energy. Both of these conditions are fulfilled by the model of strong-correlation fluctuations in a Fermi-liquid matrix. 

According to the discussion of Fig. 3, these last features are the signature for strong-correlation fluctuations in a Fermi liquid that approaches the Mott-Hubbard transition from the itinerant-electron side. We should, therefore,... 

Fig. 43. Tentative phase diagram for the system La2 xSrxCu04. scfs = strong-correlation fluctuations...

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