We solve a recently derived kinetic equation for a dilute quantum system at arbitrary degeneracy and polarization, M. From this equation we develop a spin hydrodynamic equation that allows the generalization of the treatment of spin waves and the Leggett-Rice effect to polarized degenerate Fermi gases. We find a transverse spin-diffusion collision time ${\tau }_{\perp }$ that is often shorter than the corresponding longitudinal collision time ${\mathrm{\tau }}_{\mathrm{\parallel }}$ that is often shorter than the corresponding longitudinal collision time ${\mathit{t}}_{\mathrm{\perp }}$. As T→0, ${\mathrm{\tau }}_{\mathrm{\parallel }}$ approaches T-independent value, in constrast to ${\mathrm{\tau }}_{\mathrm{\perp }}$∼1/${\mathit{T}}^2$. Spin waves would thus continue to be damped even to T=0 K.

A structure with quasiperiodicity in two dimensions and periodicity in the third has been generated by projection from 6D space. The effect of simultaneously distorting along one axis the 6D cubic cell as well as the icosahedron formed by the projection of the 6D unit vectors onto physical space has been examined for the first time. Some examples are considered to illustrate the generation of structures with P5¯mm, P${10}_5$/mcm, and P10/mmm symmetry.

The Read-Shockley treatment of small-angle grain boundaries in crystals is generalized to the case of quasicrystals. The dependence of the grain-boundary energy on the angle of mismatch between abutting quasicrystalline grains is calculated. It is found that, even for a symmetric tilt boundary in a quasicrystal, dislocations with at least two types of Burgers vectors are required; these dislocations have to be arranged quasiperiodically along the boundary. The possible clumping of these dislocations to form composites is discussed. Explicit calculations are presented for a pentagonal quasicrystal.

We distinguish the roles of the Laplace and diffusion fields in electrochemical deposition during growth of the dense-branching morphology. The shape of the growth is controlled by the Laplace field; the microscopic morphology is characteristic of diffusion-field-controlled growth; and the branch size length scale is hypothesized to be the result of the interplay of the two fields. The branching rate varies with system parameters so as to select an apparently constant interfacial velocity.

Containerless undercooling in an electromagnetic levitation device was used to observe solidification velocities as a function of undercooling temperature for pure Ni and Cu-Ni alloys. In a limited temperature range, the results can be interpreted using current theories, provided the conditions for local equilibrium at the solid-liquid interface are relaxed. Beyond a certain undercooling value, the observations differ markedly from current predictions.

Free-electron absorption of 1064-nm photons is measured photoacoustically in NaCl and ${\mathrm{SiO}}_2$. The electrons are generated with a 266-nm pump pulse by two- or three-photon transitions. For a given pump pulse energy, the photoacoustic signal and the rise in lattice temperature are observed as a function of the energy of the 1064-nm pulse and found to be in agreement with the theory of free-carrier heating. Temperatures approaching the melting point are produced in these materials under prebreakdown conditions. No evidence of electron-impact ionization and ensuing avalanche formation is found up to the intrinsic damage threshold.

We present a new type of localization phenomenon in a one-dimensional tight-binding model with a quasiperiodic potential ${\mathit{V}}_{\mathit{n}}$=tanh[Acos(2πωn)]/tanhA, where ω is an irrational number. When A is small, the localization starts from the center of the spectrum at a value of λ; then the mobility edges move towards the edges of the spectrum with increasing λ; finally all the states become localized. This behavior is in contrast to the Anderson localization in three-dimensional random systems. When A is large, a more complicated behavior is found.

A calculation is presented of the self-energy of an electron from the screened exchange energy. Vertex corrections are included. They have a large effect upon the predictions of the width of the occupied energy bands. For aluminum the band-width is predicted to be 0.7 eV wider in the GW approximation compared to GWΓ which includes vertex corrections. Results using the GWΓ approximation are similar to those of the random-phase approximation.

Contacts between heavily doped and moderately doped n-type silicon deviate drastically from conventional junctions upon shrinkage in size. Their resistance increases with increasing current injection, indicating a dipole of electron pileup and depletion near the resistivity discontinuity. Such microjunctions thus represent not the previously assumed ideal contacts but rather a novel type of Schottky barrier.

We present a systematic investigation of the influence of cross geometry on the Hall effect in narrow ballistic wires. Various differently shaped cross regions have been fabricated, which demonstrate that near zero magnetic field the Hall resistance can be quenched, enhanced over its classical value, or even negative. A ‘‘last plateau’’ is seen in all devices, proving that its cause is not intimately linked to the quenching. A simple physical picture is presented showing how these effects come about from the scattering of electrons in such geometries.

The magnetic susceptibility along the c axis (${\mathrm{\chi }}_{\mathrm{c}}$) and in the basal plane (${\mathrm{\chi }}_{\mathrm{b}}$) has been measured on a single crystal of Gd in the reduced temperature range 4×${10}^{\mathrm{-}4}$${10}^{\mathrm{-}2}$. Uniaxial anisotropy is observed. Magnetic dipole-dipole interactions are shown to account for the magnitude of the uniaxial anisotropy and also to lead to complex crossover effects. The observed temperature dependence of ${\mathrm{\chi }}_{\mathrm{c}}$(T) and ${\mathrm{\chi }}_{\mathrm{b}}$(T) is described by effective exponents ${\gamma }_{\mathrm{eff}}$=1.23±0.02 and 1-${\mathrm{\alpha }}_{\mathrm{eff}}$=1.01±0.03, respectively.

Well resolved multifrequency ${\mathrm{\mu }}^{+}$ spin-resonance spectra were observed as function of field direction and temperature in a single crystal of ${\mathrm{PrNi}}_5$. Two interstitial ${\mathrm{\mu }}^{+}$ positions were identified. A ${\mathrm{P}}_{\mathrm{x}}$(cosθ) term, in addition to ${\mathrm{A}}_0$, is sufficient to describe the angular dependence. Neither the angular dependence nor the temperature dependence of the shifts can be accounted for by Pr magnetic moments. Evidence is provided for magnetic moments at Ni sites, contradicting prevailing views.

Frequency moments of the light-scattering spectrum from spin-pair excitations are calculated for the spin-½ planar Heisenberg antiferromagnet. The quantitative agreement with the experimental $B_{1g}$ spectrum in ${\mathrm{La}}_2$Cu${\mathrm{O}}_4$ demonstrates that the observed linewidth is dominated by quantum fluctuations and yields a value for the exchange parameter $J$ of 1030±50 ${\mathrm{cm}}^{-1\mathrm{}}$. Quantum fluctuations also permit light scattering due to diagonal-next-neighbor spin-pair excitations. Observed spectral features in the $A_{1g}$ and $B_{2g}$ symmetries are consistent with those calculated for this process.

The spin-polarized sulfur ${\mathrm{L}}_2$,3VV Auger spectrum is recorded for the system c(2×2)S/Fe(001). Convolution of the calculated spin-dependent projected local density of states gives good agreement with the measured spectrum. As in previous studies a strong satellite is observed in the Auger spectrum and this is shown to be due to the presence of hybridized iron states at the sulfur site. The spectrum also shows an exchange splitting of 0.2 eV in reasonable agreement with the calculation. The integrated spin-up and spin-down Auger intensity gives an estimate of the magnetic moment of the sulfur adsorbate ≤0.10${\mathrm{\mu }}_{\mathrm{B}}$.

Ferroelectricity in ${\mathrm{Zn}}_{\mathrm{x}}$${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$Te was found from the temperature variation of the dielectric constant, and from the hysteresis loop. The Zn contents varied from 4% to 45%. No ferroelectricity was found in pure CdTe but all samples containing Zn had a second-order ferroelectric transition. The transition temperature varied from 90 to 245 °C. The polarization was in a 〈111〉 direction. While no existing model matches the rapid rise of the Curie constant for 0<x<0.04, there is some evidence to support an order-disorder transition.

Berry’s phase is defined for the dynamics of electrons in periodic solids and an explicit formula is derived for it. Because of the special torus topology of the Brillouin zone a nonzero Berry phase is shown to exist in a one-dimensional parameter space. Symmetry of the Bloch functions in the Brillouin zone leads to the quantization of Berry’s phase. A connection is established between the latter and the Wyckoff positions in the crystal in the framework of band representations of space groups. Berry’s phase can therefore be used for labeling energy bands in solids.

${\mathrm{La}}_{2\mathrm{-}\mathrm{x}}$${\mathrm{Ba}}_{\mathrm{x}}$${\mathrm{CuO}}_4$ has been found to undergo the following sequence of transformations upon cooling: tetr.(I4/mmm) →ortho.(Bmab)→tetr.(P$4_2$/ncm), over a range of composition 0.05<x<0.20. The newly discovered low-temperature tetragonal phase can be thought of as a coherent superposition of the twin-related Bmab structures. The system can be modeled as an XY-spin system with temperature-dependent quartic anisotopy, v(T). Slight differences between orthorhombic and tetragonal structures appear to have large effects upon the superconductivity.

We investigate the statistical mechanics of a simple lattice model for the denaturation of the DNA double helix. The model consists of two chains connected by Morse potentials representing the H bonds. We determine the temperature dependence of the interstrand separation and we show that a mechanism involving an energy localization analogous to self-focusing may initiate the denaturation.

A simple model is introduced to describe the observed coexistence of gelation and phase demixing in atactic polystyrene solutions. It is shown that the multiple equilibria conditions for molecular clustering caused by physical cross linking can lead to a characteristic feature of the phase diagram. The condition is examined for the appearance of new critical phenomena, such as a tricritical point or a triple point (or a three-phase equilibrium) as a result of interference between gelation and phase separation.

We study the roughening of a growing surface near to a morphological transition within a general scaling framework. For a class of systems, where the transition can be related to directed percolation, the anomalous roughness at the critical point is at most logarithmical. In two-dimensional simulations we find ${\mathrm{w}}^2$∼logL where w is the width of the surface and L is the substrate size.