The distinctive peak shapes observed in diffraction studies of the icosahedral phases of Al-Mn, Al-Li-Cu, and related alloys are shown to arise from a specific configuration of quenched phason strains in a grain. This configuration is determined by considerations of symmetry and continuity of the phason field. Al-Mn and Al-Li-Cu peak shapes are explained by minor variations of a single mechanism.

Several structural features, including electron transfer between atoms of different electronegativity, oxygen deficiency, and unsynchronized resonance of valence bonds, as well as tight binding of atoms and the presence of both hypoelectronic and hyperelectronic elements, cooperatre to confer metallic properties and high-temperature superconductivity on compounds such as (Sr,Ba,Y,La${)}_2$${\mathrm{CuO}}_{4\mathrm{-}\mathrm{y}}$. .AE

The properties of a model to describe the ${\mathrm{CuO}}_2$ planes in the high-${\mathrm{T}}_{\mathrm{c}}$ superconductors are discussed in the strong-coupling limit. On the assumption that doping creates holes on the O rather than the Cu sites, following the recent suggestion of Emery, it is shown that antiferromagnetic ordering of the Cu moments will lead to either localization or pairing of the O holes. The effect of magnetic anisotropy on the pairing interaction is discussed, and it is suggested that it will strongly enhance superconductivity in these systems.

The Eliashberg equations for magnetic fluctuations are solved for the case of ${\mathrm{UPt}}_3$. As input, the neutron data of Aeppli et al. are used for the spectral function, and the results of band-structure calculations are used to model the Fermi surface. The results indicate a mass renormalization factor of about 16, a value confirmed by comparisons of band calculations to de Haas–van Alphen data. Moreover, a superconducting transition temperature of the order of 0.1–0.2 K is calculated (due to the momentum dependence of the susceptibility) with polar gaps in parts of the zone.

The electron-stimulated desorption yields of ${\mathrm{O}}^{\mathrm{-}}$ from ${\mathrm{O}}_2$ condensed on a platinum substrate, with a rare-gas spacer layer between the ${\mathrm{O}}_2$ and Pt, are reported. The results differ dramatically from those found in the gas phase. These differences are interpreted in terms of the image charge induced in the metal.

A new maganese-related isotropic electron-spin-resonance signal at g=2.77 has been observed in GaAs. It is shown to arise from the neutral Mn acceptor, ${\mathrm{Mn}}^0$. The analysis gives an answer to the longstanding question of whether the structure of ${\mathrm{Mn}}^0$ correponds to the 3${\mathrm{d}}^4$ or to the 3${\mathrm{d}}^5$+hole. The data clearly favor the latter case, thus revealing that Mn is an exception within the 3d acceptor family in GaAs.

We show that Nosromanē mechanics provides a link between computer simulations of nonequilibrium processes and real-world experiments. Reversible Nose¯ equations of motion, when used to constrain non- equilibrium boundary regions, generate stable dissipative behavior within an adjoining bulk sample governed by Newton’s equations of motion. Thus, irreversible behavior consistent with the second law of thermodynamics arises from completely reversible microscopic motion. Loschmidt’s reversibility paradox is surmounted by this Nose¯-Newton system, because the steady-state nonequilibrium probability density in the many-body phase space is confined to a zero-volume attractor.

In contrast to the strong difference observed in the static-structure factors of icosahedral and glassy PdSiU samples of their dynamical properties as reflected in their generalized vibrational density of states are nearly identical and quite different from that of the fully crystallized samples. Low-energy modes are detected in the generalized vibrational density of states of the icosahedral phase, which lead to an enhanced intensity at energies below 10 meV as compared to that of the crystallized samples. Also the wavelength dependence of the low-energy modes in icosahedral PdSiU is very similar to that in the metallic glass.

We report the measurement of spin diffusion at zero field, observed by two-dimensional deuterium magnetic resonance of a polycrystalline sample. This demonstrates for the first time an appealing feature of pulsed zero-field magnetic resonance, namely the potential for structure determination in solids without the need for single crystals or oriented samples.

Unusual structure and large electric-field–induced oscillations have been observed in the current-voltage curves of small-area tunnel junctions arranged in a low-capacitance (≲1 fF) multiple-junction configuration. This behavior arises from the tunneling of individual electrons charging and discharging the capacitance. The observations are in accord with what would be expected from a simple model of the charging energies and voltage fluctuations of e/C associated with such effects.

This Letter is concerned with effective interatomic potentials in metals specifically arising from electronic quantum fluctuations. The cohesive energy is shown to contain large terms arising from generalized dispersion forces. Further, the density-density response function of the homogeneous electron gas is shown to contain a part decaying monotonically as 1/${\mathrm{r}}^6$ in real space; this has consequences in the construction of generalized functional theories of interatomic potentials.

The XY and the anisotropic Heisenberg models are considered above the Kosterlitz-Thouless transition temperature. Under the assumption of a gas of freely moving vortices, it is shown that the dynamic structure factor exhibits a central peak for both in-plane and out-of-plane correlations, in good agreement with the results of a combined Monte Carlo–molecular dynamics simulation. These results are also consistent with recent neutron-scattering data on ${\mathrm{Rb}}_2$${\mathrm{CrCl}}_4$ and ${\mathrm{BaCo}}_2$(${\mathrm{AsO}}_4$${)}_2$, which show qualitatively the same wave-vector and temperature dependences.

The properties of the Gutzwiller variational wave function, which is frequently used to study ground-state properties of correlated fermions with a short-range interaction, are investigated by use of a new, analytically tractable approach. As a first application several ground-state quantities are evaluated exactly in dimensionality d=1 for arbitrary band-filling and interaction strengths. The results allow for the first approximation-free assessment of the wave function. The method itself is applicable to arbitrary space dimensions.

The electron tunneling through quantized states in an ultrathin hydrogenated amorphous silicon (a-Si:H) layer sandwiched with stoichiometric silicon nitride (a-${\mathrm{Si}}_3$${\mathrm{N}}_4$:H) barriers has been systematically investigated. The I-V characteristics have exhibited the current bumps arising from the resonant tunneling through the double barriers. The effective mass of tunneling electron is obtained to be 0.6${\mathrm{m}}_0$, being consistent with the value determined from the optical band-gap data for a-Si:H/a-${\mathrm{Si}}_3$${\mathrm{N}}_4$:H multilayers.

The ac magnetic susceptibility of the spin-glass ${\mathrm{Eu}}_{0.4}$${\mathrm{Sr}}_{0.6}$S is found to have a power-law dependence on frequency near the freezing temperature. Extrapolating to zero frequency causes the peak in the real component to sharpen and shift to a lower temperature ${\mathrm{T}}_{\mathrm{c}}$. That ${\mathrm{T}}_{\mathrm{c}}$ marks a phase transition is supported by exponents describing the divergence of the relaxation time, development below ${\mathrm{T}}_{\mathrm{c}}$ of the order parameter ${\mathrm{q}}_{\mathrm{EA}(\mathrm{T}}$), suppression of ${\mathrm{T}}_{\mathrm{c}}$ by a magnetic field, and scaling of the nonlinear susceptibility.

We have observed large discrepancies between the dc magnetization and ferromagnetic resonance (FMR) magnetic anisotropy in Mo-Ni superlattices. We show that higher-order anisotropy is present in both measurements and develop an analysis by which the first-order and second-order energies can be treated independently. The low-temperature results show a systematic divergence of the first-order FMR and dc anisotropy as the Ni-layer thickness decreases. It is shown that the source of the divergence is an enhanced surface anisotropy measured by FMR. Possible sources of this enhancement are discussed.

Electron-stimulated desorption of ${\mathrm{H}}^{\mathrm{-}}$, ${\mathrm{O}}^{\mathrm{-}}$, and ${\mathrm{OH}}^{\mathrm{-}}$ ions from a metal-deposited multilayer ${\mathrm{O}}_2$ film covered with ${\mathrm{C}}_{\mathrm{n}}$${\mathrm{H}}_{2\mathrm{n}+2\mathrm{}}$ molecules is reported for the incident energy range 5–20 eV. By producing selectively with the electron beam ${\mathrm{O}}^{\mathrm{-}}$${(\mathrm{}}^2$P) ions on the film, via the dissociative attachment reaction ${\mathrm{O}}_2$${(}^3$${\mathrm{\Sigma }}_{\mathrm{g}}^{\mathrm{-}}$)+${\mathrm{e}}^{\mathrm{-}}$→${\mathrm{O}}_2^{\mathrm{-}}$${(}^2$${\mathrm{\Pi }}_{\mathrm{u}}$${,}^2$${\mathrm{\Sigma }}_{\mathrm{g}}^{+}$) →${\mathrm{O}}^{\mathrm{-}}$${(\mathrm{}}^2$P)+O${(\mathrm{}}^3$P), the surface reaction ${\mathrm{O}}^{\mathrm{-}}$+${\mathrm{C}}_{\mathrm{n}}$${\mathrm{H}}_{2\mathrm{n}+2\mathrm{}}$→${\mathrm{OH}}^{\mathrm{-}}$ +${\mathrm{C}}_{\mathrm{n}}$${\mathrm{H}}_{2\mathrm{n}+1\mathrm{}}$ can be induced and controlled.

We present an analytic derivation of a chiral-symmetry-breaking transition in (zero-temperature) U(1) and $Z_N$ lattice gauge-Higgs theories with fermions. Several remarkable properties of this transition are discussed. Implications for confining models of weak interactions are noted.

We show that while the exactly integrable spin-(3/2 Heisenberg antiferromagnet is a representation of the nonlinear σ model with nontrivial Wess-Zumino term, the generic massless antiferromagnet has long-wavelength behavior equivalent to spin (1/2. This is demonstrated by comparing the predictions of conformal symmetry and rotational symmetry to the gaps calculated for finite chains. The leading corrections are eliminated leading to stable estimates of the conformal central charge and exponents for the spin-correlation functions.

We show through all-electron first-principles electronic structure calculations of core levels that, contrary to previous expectations, the valence-band offsets in the common-anion semiconductors AlAs-GaAs and CdTe-HgTe are decided primarily by intrinsic bulk effects and that interface charge transfer has but a small effect on these quantities. The failure of previous models is shown to result primarily from their decision to omit cation d orbitals.