We investigate the formation of nucleating droplets in the neighborhood of the classical spinodal in systems with long-range forces. We find that the droplets are formed by the coalescence of several clusters that are associated with the critical phenomena fluctuations at the spinodal.

Structural studies on aqueous solutions of PEO-PPO-PEO block copolymers show three phases as the temperature is varied. At low T, the tri-block units are dissolved Gaussian chains. As T is increased still more unimers aggregate in micelles, until a volume fraction of 0.52 is reached. The micelles then crystallize in a body-centered-cubic lattice. Upon the application of a small shear, the high-T polycrystalline phase abruptly transforms into a single crystal, characterized by only quasi-long-range order in bond length, but true long-range correlations in the bond angle.

The temperature dependence of the characteristic length for the dynamic glass transition in ortho-terphenyl is determined, for the first time, from combined results of depolarized dynamic light scattering, photon correlation spectroscopy, and viscosity experiments. The length is found to vary according to ${\xi }_{\mathit{a}}$∼(T-${\mathit{T}}_{\mathrm{\infty }}$${)}^{\mathrm{-}\nu }$ where ${\mathit{T}}_{\mathrm{\infty }}$ is the Vogel temperature, with an exponent ν-0.69±0.06 in the temperatur region from up ${\mathit{T}}_{\mathit{g}}$ up to ${\mathit{T}}_{\mathit{g}}$+80 K.

The isotope effect E=(${\mathit{D}}_{\mathrm{\alpha }}$/${\mathit{D}}_{\mathrm{\beta }}$-1)/[(${\mathit{m}}_{\mathrm{\beta }}$/${\mathit{m}}_{\mathrm{\alpha }}$${)}^{1/2}$-1] of cobalt diffusion has been measured in melt-spun amorphous ${\mathrm{Co}}_{76.7}$${\mathrm{Fe}}_2$${\mathrm{Nb}}_{14.3}$${\mathrm{B}}_7$ ribbon at different stages of structural relaxation. A drastic drop of the isotope effect from E>0.5 in the as-quenched glass to E=0.1 in the relaxed state wass observed. While the latter value relflects highly cooperative diffusion, the large isotope effect in the as-quenched ribbon points to the prevalence of single-atom jumps and vacancylike holes of excess volume.

We have measured the 2D ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ superfluid density ${\mathrm{\sigma }}_{\mathit{s}}$ on hydrogen using a high-Q Al oscillator. We find that only 1/2 layer of helium remains normal well below the transition on hydrogen as opposed to 4 layers on bare Al. For transition temperatures ${\mathit{T}}_{\mathit{c}}$ below 0.9 K we find that ${\mathrm{\sigma }}_{\mathit{s}}$(${\mathit{T}}_{\mathit{c}}$)∝${\mathit{T}}_{\mathit{c}}$ as predicted by Kosterlitz-Thouless theory. For transitions above 1 K, where there is significant vapor damping, we see a striking suppression of ${\mathrm{\sigma }}_{\mathit{s}}$(${\mathit{T}}_{\mathit{c}}$) and find clear evidence for the appearnace of excess gas-atom slip in the superfluid phase.

We study a class of generalized car-parking problems and show analytically that whereas the properties (structure and density) of the configurations generated by the generalized and the standard parking processes are different at most times, they are identical at the jamming limit (t→+∞). We indicate how such models can be used to describe more realistic particle deposition processes which combine bulk diffusion and irreversible adsorption. This provides a theoretical basis to explain recent simulation results.

Phase transformation dynamics is of current interest in terms of the scaling behavior of the growth law and the prediction of self-similar cluster size distributions. We present the first experimental data to test model predictions for coalescence, showing that recent Monte Carlo simulations agree with measurements for Ga on GaAs(001). Detailed aspects of the growth and the relationship to the theoretical assumptions are discussed.

Time- and energy-resolved fluorescence methods with synchrotron radiation excitation are used to investigate excitation and decay processes of electronically excited ${\mathrm{XeAr}}_{\mathit{N}}$ clusters (N=20–5000). For excitations related to the first resonance transition of Xe, pronounced size and site effects are reported. In particular, three distinct sites of atomic Xe are established. Selective excitation of Xe on top of the cluster surface results in an escape of the electronically excited atom, whereas Xe atoms initially located in the interior of the cluster remain after electronic excitation in interior of the cluster.

The interaction of an optically induced nonstationary electron-hole plasma with coherently excited optical phonons in GaP has been investigated through time-resolved coherent anti-Stokes Raman spectroscopy. Nonexponential optical-phonon dephasing is observed in the presence of the electron-hole plasma. A model describing the interaction between the optical phonons and the electron-hole plasma is presented. A comparison of results from the theoretical model and from the experimental data indicates good agreement.

We have studied through real-time numerical simulations the question of polaron formation by a single electron injected in a band consisting of fluctuating amplitude or mobility edge eigenstates. We found that polaron formation depends strongly on how close to a mobility edge the initial state is, on its average energy, and, to a much lesser degree, on its shape. In some instances novel highly excited long-lived localized polarons appear. In general, the time evolution exhibits an unexpected behavior; even for very long times, the electron does not seem to transfer much of its energy to the lattice.

We report neutron inelastic scattering measurements of the dispersion of the phase mode of the charge-density-wave (CDW) collective excitations in the blue bronze. Anisotropy and temperature-dependence analysis yields phase elasticity parameters relevant for a classical deformable model of CDW. The considerable stiffening of the longitudinal phason velocity observed upon cooling clearly shows that Coulomb forces play a fundamental role in CDW deformation processes.

The attenuation of the Cu ${\mathit{M}}_{2,3}$VV Auger peak with Cs coverage on Cu(100) was measured using positron-annihilation-induced Auger electron spectroscopy (PAES) and conventional (electron-induced) Auger electron spectroscopy. The data (obtained at both 303 and 163 K) indicate that below a critical coverage (∼0.7 monolayer) the positrons are trapped at the Cu/Cs interface in agreement with theoretical calculations. We observe a sharp (less than 0.02 monolayer wide) drop in the normalized PAES intensity at the critical coverage indicating a transition to another position state in which the positrons are localized on the vacuum side of the Cs overlayer.

The effective partition function of a fractional quantum Hall system, which is described by the Laughlin quasiparticle wave function, is obtained in the path-integral representation. It shows that the quasiparticles cannot be treated as ordinary anyons in view of the freeze of the kinetic energy and the ‘‘bosonic aspect’’ of the Hilbert space. By using the constrained anyon systems, we find that one type of filling fractions is more stable than other fractions predicted by the standard hierarchy theory. This work also sheds considerable light on the possible equivalence between the hierarchy theory and the composite-fermion approach proposed by Jain recently.

We provide a theoretical basis for Clark’s proposal that for quantum Hall liquids at magic filling factors, where the longitudinal conductivity is exponentially activated, ${\mathrm{\sigma }}_{\mathit{x}\mathit{x}}$=${\mathrm{\sigma }}_{\mathit{x}\mathit{x}}^0$${\mathit{e}}_{\mathit{B}}^{\mathrm{-}\mathrm{\Delta }/\mathit{k}}$T, the prefactor ${\mathrm{\sigma }}_{\mathit{x}\mathit{x}}^0$ is proportional to the square of the quasiparticle charge. We also propose that the same experiments uncover a remarkable law of corresponding states.

The microwave surface resistance at 2.95 GHz of a very-high-quality crystal of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ exhibits unusual nonmonotonic temperature dependence. After a sharp drop below ${\mathit{T}}_{\mathit{c}}$ by a factor of 5000 the loss rises to a peak at 35 K and then falls at lower temperature. The peak is due to a rapid decrease in the scattering of thermally activated quasiparticles below ${\mathit{T}}_{\mathit{c}}$ and this suppression of scattering suggests that the excitations responsible for the large resistivity of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ are gapped below ${\mathit{T}}_{\mathit{c}}$. A technological implication is that disorder may lower the microwave loss.

We have observed Josephson coupling between CuO double layers in ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_8$ single crystals by direct measurements of ac and dc Josephson effects with current flow along the c axis. The results show that a small ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_8$ single crystal behaves like a series array of Josephson junctions which can exhibit mutual phase locking.

The physics of flux lines in the cuprate superconductors pinned by columnar defects is mapped onto boson localization in two dimensions. The theory predicts a Bose glass phase with an infinite tilt modulus and zero linear resistivity, as well as an entangled flux liquid. We describe correlations and transport in these phases, and propose a scaling theory for the irreversibility line which separates them.

We study variationally the possible occurrence of a Luttinger liquid in the normal state of the 2D t-J model. For this, we generalize to 2D a Luttinger-Jastrow-Gutzwiller-type wave function introduced by Hellberg and Mele for the 1D t-J model. We show that this wave function does show also in 2D the characteristic correlations of a Luttinger liquid and the gains in kinetic energy stabilize the Luttinger liquid state with respect to Fermi liquid states with short-range correlations only. In addition, we provide rigorous lower bounds to the transition to the fully phase separated state at larger ratios J/t.

We show that the geometrical (Berry) phases discovered in Hamiltonian systems can also be defined as resulting from parallel transportation of vectors for nonlinear dissipative systems with cyclic attractors. If the nonlinear dissipative systems possess a certain kind of asymptotic solution defined in this Letter, the phase and amplitude accumulation of a geometrical type can be defined. Detuned one- and two-photon lasers showing periodic intensity pulsations are taken as examples of such systems.

We present the results of numerical calculations of internal fractal dimensions of a dynamically triangulated two-dimensional gravity coupled to c=-2 matter. Internal fractal dimensions as a function of internal geodesic distance are measured from the number of boundaries and the total length of boundaries, and show clear scaling behavior, while the number of triangles starts to scale only around the maximum size. We apply a recursive sampling algorithm for c=-2, which makes it possible to generate the most probable triangulations of spherical topology, consisting of 5×${10}^6$ triangles.