Simulations of the long-time behavior of the Zakharov model of Langmuir turbulence in two spatial dimensions reveal regimes where nucleation of localized electrostatic fields in previously burnt out density cavities is the mechanism which sustains the turbulence. Power spectrum diagnostics show that for moderate ion wave damping the Langmuir energy is carried by localized states.

Calculations of the Gibbs free energies of single-crystal and multiply twinned small metal particles clearly indicate for the first time both the presence of a quasimolten phase (where the particles are continuously fluctuating between different structures) at temperatures well below the melting point and the existence of distinct phase regions for different particle shapes. These results have important implications for the understanding of epitaxial growth processes; for instance, at temperatures where the quasimolten and single-crystal phases are contiguous one would expect far better epitaxial growth than at temperatures where the multiply twinned phases are stable.

The thermodynamic and kinetic conditions for the phase separation of a metastable reactive system are formulated. The lifetime of a metastable state is defined and its dependence on the extent of the quench and on the chemical reaction rates is found. When the chemical reaction is too fast the system will not separate into two phases even if such a separation is allowed by thermodynamics.

Ultrasonic measurements of static ${\mathrm{c}}_{44}$ shear elastic constants in K(CN${)}_{\mathrm{x}}$${\mathrm{Cl}}_{1\mathrm{-}\mathrm{x}}$, K(CN${)}_{\mathrm{x}}$${\mathrm{Br}}_{1\mathrm{-}\mathrm{x}}$, and Rb(CN${)}_{\mathrm{x}}$${\mathrm{Br}}_{1\mathrm{-}\mathrm{x}}$ mixed crystals are reported and analyzed with a recent mean-field theory including random strain fields. The good agreement between theoretical predictions and the present experiments clearly supports the suggestion that there exists a pretransitional temperature regime where the static shear elastic behavior can be understood in terms of competition between cyanide quadrupolar pseudospin lattice-mediated nonrandom interactions and quenched random strain fields.

We report the first identification of the phase of superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ in a geometry confined on the scale of the correlation length. For a wide range of pressures and temperatures at which the B phase is stable in bulk, the A phase occurs in thin films. The order-parameter structure is deduced by nuclear magnetic resonance. Simultaneous measurements of the superfluid density monitor the magnitude of the energy gap. We demonstrate that the boundary condition on the order parameter is tunable. Pair breaking is reduced dramatically at surfaces covered by adsorbed monolayers of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$.

We report observation of microcrystalline interface phases at the ${\mathrm{SiO}}_2$-Si(001) interface. The crystallites have varying degrees of orientational order with respect to the substrate depending on preparation techniques. Most of the diffraction peaks from these phases can be indexed as due to the α-cristobalite structure. Data are presented for oxides prepared on Si(001) surfaces by thermal oxidation, by electron beam evaporation, and by native oxide formation.

Experimental evidence is presented showing that the creation of vortices in He II involves macroscopic quantum tunneling through, or thermal activation over, a potential-energy barrier ε. The investigations, based on measurements of the rate at which negative ions create vortex rings in the isotopically pure superfluid within the temperature range 50<T<500 mK, have yielded a barrier height of ε/$k_{\mathrm{B}=3.1\mathrm{}\pm 0.1}$ K, in excellent agreement with the theoretical value predicted by Muirhead, Vinen, and Donnelly.

A long-wavelength lattice-dynamical calculation of the elastic and piezoelectric tensors that does not use the adiabatic approximation yields linear coupling to rotation as well as to strain in dynamic interactions. This leads in the general anisotropic case to 45 independent elastic components (rather than 21 as believed for over a century) and to 27 independent piezoelectric components (rather than 18). The new coupling should be observable at temperatures close to a second-order phase transition where a zone-center soft mode has fallen into the hypersonic region.

Scaling structures of the growth probability distribution are studied for a two dimensionally grown irregular fractal-like dendrite of ammonium chloride, whose fractal dimension coincides with that of diffusion-limited aggregation. Three different kinds of probability measure are brought into the analysis, i.e., growth site area, normal growth velocity obtained from two successive pictures, and the potential gradient calculated from the Laplace equation. Generalized dimensions D(q) with q=-∞,0,1,∞ are in good agreement with those obtained by the recent off-lattice diffusion-limited-aggregation simulation and theory.

Neutron diffraction shows that superconducting ${\mathrm{UPt}}_3$ can be an antiferromagnet with an ordered moment of (0.02±0.01)${\mathrm{\mu }}_{\mathrm{B}}$ and a Néel temperature (${\mathrm{T}}_{\mathrm{N}}$) of 5 K. The squared order parameter is linear function of temperature from ${\mathrm{T}}_{\mathrm{N}}$ to the superconducting transition temperature, ${\mathrm{T}}_{\mathrm{c}}$=0.5 K, below which it ceases to evolve. Inelastic neutron scattering demonstrates that the fluctuating moments are strongly correlated; the characteristic energy for fluctuations with wave vectors close to the ordering wave vector is 0.2 meV≊4${\mathrm{kT}}_{\mathrm{c}}$..AE

In a magnetic field, a wave function in a two-dimensional system is uniquely specified by the position of its nodes. We show that for high fields and a weak random potential, motion of the zeros of the wave function under smooth changes of the boundary conditions can be used to characterize the behavior of the one-electron states and distinguish between localized and extended states.

We show that antiferromagnetic correlations with frequencies scaling as the inverse-mass enhancement are universal features of coherent heavy fermions. The associated neutron cross-section peaks may be either quasielastic or inelastic. Spin-orbit and crystal-field interactions yield zone-center peaks at comparable frequencies. This experimentally observed behavior is derived from a 1/N expansion. Because these correlations are not ‘‘soft’’ and are general features of hybridized band structure, they do not necessarily elucidate the superconducting mechanism.

The small-signal impedance of chemical cells with ‘‘blocking’’ electrodes is dominated at low frequencies (f<∼100 Hz) by the impedance of the metal-electrolyte interfaces which is accurately represented by ${\mathrm{Z}}_{\mathrm{i}}$=A(jω${)}^{\mathrm{-}\mathrm{n}}$. The frequency exponent n, n<1, is sensitive to the texture of the interface, and several recent theories have been proposed that relate n with the fractal dimension d¯ of the rough interface. We find no correlation between n and d¯ from experiments using aqueous electrolytes and metal and semiconductor electrodes.

The crossover between 2${\mathrm{k}}_{\mathrm{F}}$ and 4${\mathrm{k}}_{\mathrm{F}}$ charge-density waves in an extended one-dimensional Hubbard model is studied in the U→∞ limit by mapping onto a Heisenberg antiferromagnet with a competing second-neighbor Ising interaction. The phase diagram is obtained by a combination of field theory techniques and numerical solution of finite chains. Regions of staggered spin order (4${\mathrm{k}}_{\mathrm{F}}$ site or bond order) and (2,2) spin order (2${\mathrm{k}}_{\mathrm{F}}$ site order) are mapped out. Critical exponents in the algebraic phase are obtained.

A set of Jastrow wave functions comprises exact eigenstates of a family of S= $\frac{1}{2}$ antiferromagnetic chains with ${\mathrm{r}}^{\mathrm{-}2}$ exchange. The ground state of the isotropic model is in this set, and is identical to the U→∞ limit of the Gutzwiller wave function, also identified as Anderson’s ‘‘resonating-valence-bond’’ state. The full set of energy levels of this model is obtained; the spectrum exhibits remarkable ‘‘supermultiplet’’ degeneracies suggesting the existence of a hidden continuous symmetry.

The S=1/2 Heisenberg Hamiltonian H=1/2${\mathcal{J}}_{\mathrm{n}=1\mathrm{}}^{\mathrm{N}\mathrm{-}1}$${\mathcal{J}}_{\mathit{m}=1\mathrm{}}^{\mathit{N}}$${\mathit{J}}_{\mathit{n}}$${\mathrm{\sigma }}_{\mathit{m}}$⋅ ${\mathrm{\sigma }}_{\mathit{m}+\mathit{n}}$, with $J_n$=$J_0$/${\sin }^2$(nπ/N), is shown to have a simple singlet ground state in the form of a Jastrow function. The spectrum and correlations are explicitly known and the magnetic susceptibility is shown to be Pauli type at T=0. The model has a striking similarity to the nearest-neighbor isotropic Heisenberg model and may be viewed as a discretized version of the Sutherland-Calogero-Moser system.

Novel time-domain data on the nuclear Zeeman effect are presented from ${}_{}{}^{67}{}_{}{}^{}\mathrm{Zn}$ Mössbauer experiments. The results are in accordance with a theory developed for magnetic phase modulation. The self-calibrating feature of the high-frequency Zeeman scanning method allows precise determination of the 93-keV-state magnetic moment of the ${}_{}{}^{67}{}_{}{}^{}\mathrm{Zn}$ nucleus. For ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ in magnetically soft materials, the present approach predicts rf-field-induced sidebands without any mechanical motion, and an associated collapse phenomenon.

A novel technique, which employs ωχ’/χ’’ of the longitudinal susceptibility in place of the shape function χ’’/ωχ(0), reveals a coupling of the heavily overdamped soft mode to a relaxation mode in the transverse Ising ferromagnet ${\mathrm{LiTbF}}_4$. Our analysis by exact Mori-Langevin equations suggests that this contribution to the central peak, which becomes temperature dependent only below ${\mathrm{T}}_{\mathrm{c}}$, arises from a dynamical coupling to the transverse polarization.

A theoretical prediction of a new spin effect by Tamura, Piepke, and Feder has been experimentally verified: Photoelectrons can be polarized even if the photoemission is performed with linearly polarized radiation and even if it is studied in the highly symmetrical setup of normal incidence and normal emission. Radiation with energies between 21 and 22.4 eV ejects photoelectrons from Pt(111) polarized with a degree between 10% and 40%. The spin direction coincides with a plane parallel to the surface and changes its sign when the crystal is rotated by 60° about the surface normal.

Whenever the escaping entity and the thermal reservoir in contact with it move at comparable rates, escape must be viewed as due to diffusion in the space of the action variables. For almost integrable systems, the effective barrier height is argued to exceed substantially the potential-energy barrier of conventional theory, at least in the common case in which the potential barrier arises from terms in the Hamiltonian responsible for the nonintegrability, and to the extent that the usual quasiperturbative treatment of almost integrable systems is applicable at energies of order of the barrier.