International Journal of Modern Physics B

The Edwards model for polymers with excluded-volume interaction has been used to study steric stabilization of colloidal dispersions since Dolan and Edwards' work in 1975. Following the standard picture of steric stabilization since 1950s, Dolan and Edwards solved the model by treating the surfaces of colloidal particles as plane surfaces. Consequently, their result was also consistent with the standard picture: Reduction of conformational entropy of the adsorbed homopolymers results in a purely repulsive force that stabilizes the colloidal dispersion. Recently the Edwards model was solved without treating the spherical particle surfaces as plane surfaces. It was found that, contrary to the standard picture, the conformational entropy indeed increases and the force between particles may be either purely attractive or attractive at large particle-particle separation, repulsive at intermediate separation, and again attractive at small separation. Thus, the standard picture of steric stabilization was challenged. This review summarizes this recent progress in the theory of steric stabilization of colloidal dispersions. Reconciliation between the standard picture and the recent result, and possible directions for further research are also discussed.

We calculate the contribution of deconfined spinons to inelastic neutron scattering (INS) in the fractionalized antiferromagnet (AF*), introduced elsewhere. We find that the presence of free spin-1/2 charge-less excitations leads to a continuum INS signal above the Néel gap. This signal is found above and in addition to the usual spin-1 magnon signal, which to lowest order is the same as in the more conventional confined antiferromagnet. We calculate the relative weights of these two signals and find that the spinons contribute to the longitudinal response, where the magnon signal is absent to lowest order. Possible higher-order effects of interactions between magnons and spinons in the AF* phase are also discussed.

The Y(M_xAl_{1 - x})₃ compounds with M = Fe or Co crystallize in BaPb₃-type structure for compositions x ≤ 0.4 while for x ≥ 0.6 the crystal structure is of PuNi₃-type. Two phases were evidenced in the intermediate composition range. Magnetic measurements were performed on Y(M_xAl_{1 - x})₃ compounds in the temperature range 5–800 K and external field up to 10 T. The compounds with x ≥ 0.8 for M = Fe and Co are ferromagnetically ordered. For x < 0.8 a short range order and freezing effects of magnetic clusters originating from replacement of Fe by Al are evidenced. The mean magnetic moments of iron clusters as well as their number are estimated. For the samples with cobalt for x = 0.4 no magnetic order, down to 4.2 K was evidenced. For all compositions, the thermal variations of magnetic susceptibilities obey Curie–Weiss type dependencies.

Magneto-transport and magnetic data on MgB₂ polycrystalline samples are reported for applied magnetic fields up to 9 T. In the normal state we find that MgB₂ compound has a temperature and field-dependent resistivity behavior like a simple metal. The critical magnetic field H_c2(T) and the irreversibility field H_irr(T) curves were determined. The Hall coefficient R_H is slightly temperature dependent. Using the extracted data, we calculated the electronic mean free path, coherency length ξ₀ and London penetration depth λ_L.

The full pattern decomposition method by Le Bail was applied to a single phase orthorhombic (Bi,Pb):2223 superconductor with an accentuated three dimensional excess conductivity. The space group Pmam, with the lattice parameters a = 5.2598, b = 5.5381, c = 37.174 Å was found. The Fourier maps derived show that delocalization of the Sr atoms induces terracing of the Cu/Ca/Cu superconducting stacking of 0.3 Å, close to the c-axis coherence length, yielding the three dimensional character of the conduction evidenced by the resistivity measurements.

A quantum resonance in the conduction through the normal-conductor–superconductor junction is investigated in the presence of a magnetic field using a numerical transfer matrix method. It is shown that dip-pairs in the conductance curve occur at a certain geometry of the system owing to the resonant reflection caused by the interference of the reflected electron and hole waves under a finite magnetic field. By examining a local density of quasiparticles, we found that the feature of the resonant state giving the dip-pair in the conductance (in a magnetic field) is very different from that in a finite bias voltage.

We have analyzed what new fundamental information on the properties of superconductors can be obtained by systematic investigation of the Bernoulli effect. We show that the latter is a tool to determine the effective mass of Cooper pairs, the volume density of charge carriers, the temperature dependence of the penetration depth and the condensation energy. To this end, the theoretical results for disordered and anisotropic-gap superconductors are systematized. For clean anisotropic-gap superconductors we present a simple derivation of the temperature dependence of the penetration depth.

We have shown in this report the application of projection operator method of group theory in deriving the wavefunctions for the surface state in Cu(110) which had been used in calculating photocurrent. This approach gives a qualitative characterization of surface states simply on the basis of existing bulk-band structure calculations.

By using canonical and unitary transformations and the Lewis–Riesenfeld invariant method, the generalized invariant and the exact Schrödinger wave functions for a time-dependent parametric oscillator with and without an inverse quadratic potential are obtained.

Within a varied Nagel–Schreckenberg model of traffic flow on one-lane highways, we study the probability of "takeover" and its effect on traffic flow. In the paper, we define the probability of takeover, and compare the results derived partially from the equation estimated accordingly with those completely obtained from the computer simulations. The probability of driver-oriented takeover is also considered.

A construction for the generation of eight-fold symmetry planar patterns is introduced. The basic building blocks are four triangle prototiles with six edge lengths. Subpatterns with three prototile shapes and two edge lengths can also be derived.