We performed electrochemical deposition of copper at very slow rates so that local growth effects such as surface relaxation and stochastic noise can compete with the nonlocal Laplacian effects. We observed that the initial growth pattern is consistent with the conventional Mullins-Sekerka instability. This is followed by coarsening and roughening of the surface that leads to a columnar structure with deep crevices. The surface roughness for length scales below the typical column width shows a power-law behavior with an exponent α=0.55±0.06, consistent with the prediction of Kardar, Parisi, and Zhang (KPZ). However, the time dependence of the total interface width is not the ${\mathit{t}}^{1/3}$ power law predicted by KPZ.

We have observed giant magnetoresistance in heterogeneous thin film Cu-Co alloys consisting of ultrafine Co-rich precipitate particles in a Cu-rich matrix. The magnetoresistance scales inversely with the average particle diameter. This behavior is modeled by including spin-dependent scattering at the interfaces between the particles and the matrix, as well as the spin-dependent scattering in the Co-rich particles.

We have observed isotropic giant magnetoresistance (GMR) in nonmultilayer magnetic systems using granular magnetic solids. We show that GMR occurs in magnetically inhomogeneous media containing nonaligned ferromagnetic entities on a microscopic scale. The GMR is determined by the orientations of the magnetization axes, the density, and the size of the ferromagnetic entities.

We present a simple cellular method for the exact solution of the single-particle Schrödinger equation of a complex system. It uses basis functions which are locally exact solutions within each potential cell. The wave-function expansion coefficients are determined by the boundary conditions between the neighboring cells, which can be specified on spheres instead of the cell boundaries. The method can yield an exact first-principles tight-binding theory with only nearest-neighbor couplings. Tests of the method using the two-dimensional empty lattice and the hydrogen molecule ion indicate that it converges rapidly and yields accurate results.

We generalize the analytic theory of universal conductance fluctuations to systems with Landau-level quantization. Results are valid to leading order in 1/g (g is conductance) but for arbitrary magnetic field. We show that the field only enters through the diffusion constant and cancels in the variance of g, which hence remains ∼(${\mathit{e}}^2$/h${)}^2$ over the entire range of magnetic fields. However, the correlation range ${\mathit{B}}_{\mathit{c}}$ does vary with field in good agreement with experiments.

Three-wave mixing was used to spectroscopically probe the interface electronic structure of a buried ZnSe/GaAs[001] heterointerface from 1.3 to 4.3 eV. An unusual resonance at 2.72 eV was observed and assigned to a virtual transition between the valence band of ZnSe and a quantum well state at the buried heterointerface. This assignment was confirmed by experiments that combine three-wave mixing with photoinduced band bending. The experiments also indicate the resonance may be a useful probe of defects at the buried interface.

We report the observation of quantum size effects in the thermal conductance and Peltier coefficient of a quantum point contact. Our experimental method involves a novel usage of quantum point contacts as local electron gas thermometers.

The two distinct peaks observed as a function of temperature in the dissipation of vibrating superconducting slabs in a tilted magnetic field are explained by thermally activated flux diffusion across the thickness and width (or length) of the slab. These conspicuous peaks thus do not necessarily indicate multiple phase transitions of the flux-line lattice as proposed previously. Anisotropic mobility of the flux lines may increase or decrease the separation of the peaks.

The temperature ${\mathit{T}}_{\mathit{s}}$ of spontaneous creation of vortex lines in Josephson coupled layered superconductors is obtained by taking into account the entropy contribution to the free energy due to thermal distortions. For Bi- and Ti-based high-${\mathit{T}}_{\mathit{c}}$ superconductors and superlattices, the superconducting critical temperature ${\mathit{T}}_{\mathit{s}}$ lies noticeably below the mean-field transition temperature ${\mathit{T}}_{\mathit{c}0}$(${\mathit{T}}_{\mathit{c}0}$-${\mathit{T}}_{\mathit{s}}$≊4 K or more). The contribution of thermal distortions to the free enery causes significant changes in the temperature and field dependences of magnetization below ${\mathit{T}}_{\mathit{s}}$ seen in Bi compounds.

The electronic and structural phase diagram of heavily doped ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_4$ (0.15≤x≤0.3) is reexamined. We demonstrate that the disappearance of superconductivity in ‘‘overdoped’’ ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_4$ is associated with an orthorhombic to tetragonal structural phase transition near x=0.2, implying a relationship between superconductivity and subtle structural change. The bulk superconducting phase is thus confined to a much narrower composition range than believed. A complete solid solution of La and Sr is observed in the composition range investigated.

We study the equilibrium behavior in a dilute system of classical Heisenberg spins coupled via the Ruderman-Kittel-Kasuya-Yoshida interaction using a hybrid Monte Carlo spin-dynamics method. We find that, even when anisotropy is absent, the system exhibits a spin-glass phase transition at a finite temperature, contrary to previous predictions.

The nearest-neighbor Heisenberg spin glass in two and three dimensions is studied by means of a T=0 domain-wall renormalization-group method with a focus on the chiral ordering. In d=2 dimensions, both the spin and chiral components order at zero temperature with different correlation-length exponents, while d=3 appears to be just above the lower critical dimension of the chiral component ${\mathit{d}}_{\mathit{l}}^{\left(\mathit{c}\right)}$, though the possibility that ${\mathit{d}}_{\mathit{l}}^{\left(\mathit{c}\right)}$=3 cannot be ruled out. A chirality driven mechanism is proposed as a new possible mechanism of experimentally observed spin-glass transitions.

Potassium clusters are incorporated into supercages of zeolite LTA crystals, with the supercages arrayed in a simple cubic structure at a number density of 5.3×${10}^{20}$ ${\mathrm{cm}}^{\mathrm{-}3}$. About four 4s electrons of K atoms are included in each cluster. The ac magnetic susceptibility increases dramatically with decreases in temperature below 8 K, and shows ferromagnetism below about 4 K. The effective magnetic moment per supercage is estimated to be about 0.13${\mathrm{\mu }}_{\mathit{B}}$ at 1.7 K. Magnetic properties resemble those of a reentrant spin glass.

We report measurements of annihilation gamma-ray spectra from the isolated two-body interaction of room-temperature positrons with a range of chemical species. The Doppler broadening of these spectra provides information about the wave functions of the annihilating particles. For a variety of hydrocarbons, we observe linewidths of approximately 2.2 keV (FWHM), while for perfluorocarbons the widths are approximately 2.8 keV, as compared with 1.7 keV for molecular hydrogen. The implications of these results for a number of physical problems are discussed.

The charge-state distribution of 0.5-MeV He ions scattered from a SnTe(001) surface has been investigated using a new technique of high-resolution high-energy ion scattering spectroscopy. The ions scattered from successive atomic layers can be resolved in the energy spectra of the scattered ions. The observed charge-state distribution of the ions scattered from the topmost atomic layer coincides with that of ions scattered from the subsurface region and does not depend on the incident charge state but depends on the exit angle. The observed exit-angle dependence is explained by a model which includes the charge-exchange process with the valence electrons in the tail of the electron distribution at the surface.

Binary mixtures of suspended hard-sphere colloidal particles, radius ratio ${\mathit{R}}_{\mathit{B}}$/${\mathit{R}}_{\mathit{A}}$=0.58, were observed to undergo entropically driven freezing transitions into both the ${\mathit{AB}}_2$ and the ${\mathit{AB}}_{13}$ superlattice structures at different relative proportions of the two species. The structures were identified by powder light crystallography and by electron microscopy of the dried solid phases. An approximate (constant volume) phase diagram containing three eutectics was determined. The results are compared with earlier work at size ratio 0.62.

A new method of quantifying correlations in symbolic sequences is applied to DNA nucleotides. Spectral density measurements of individual base positions demonstrate the ubiquity of low-frequency 1/${\mathit{f}}^{\mathrm{\beta }}$ noise and long-range fractal correlations as well as prominent short-range periodicities. Ensemble averages over classifications in the GenBank databank (primate, invertebrate, plant, etc.) show systematic changes in spectral exponent β with evolutionary category.

Although originally thought to show great promise in solving quantum many-body problems on a lattice, numerical real-space renormalization-group techniques have had little success for such problems. We explore the nature of the difficulties involved by studying the applicaton of the method to the simple tight-binding model in one dimension. The standard approach fails dramatically for this model. We show that the key to successfully applying the renormalization-group technique lies in applying a variety of boundary conditions to a block in order to simulate the effect of neighboring blocks.

We examine quantum chaotic scattering in the semiclassical regime for the two cases where the classical scattering is hyperbolic and nonhyperbolic. It is shown that in the nonhyperbolic case the energy-dependent S-matrix autocorrelation function C(ɛ) exhibits a cusp-shaped peak at ɛ=0 (where ɛ denotes the energy difference). This indicates that the fine scale fluctuations with energy of the S matrix are characteristically greatly enhanced in the nonhyperbolic case as compared with the hyperbolic case.

Coupled map lattices with asymmetric short-range couplings are studied analytically and numerically. It is shown that with open boundary conditions these systems exhibit spatially uniform, but temporally chaotic states that are stable even in the thermodynamic limit. The stability of this state is associated with the appearance of a gap at zero wave number in the spectrum of the linear operator describing the fluctuations about the uniform state. The long-range order is unstable to noise. We calculate the finite coherence length of the chaotic state in the presence of weak noise.