A short, intense current pulse (I=150 A, Δt≃0.2 μs, N≃2×${10}^{14}$ electrons) is drawn from an electrode immersed in a magnetized afterglow plasma (n≃2×${10}^{11}$ ${\mathrm{cm}}^{\mathrm{-}3}$, ${\mathit{kT}}_{\mathit{e}}$≃1.3 eV, ${\mathit{B}}_0$=10 G). The induced magnetic field B(r,t) assumes the shape of a helical double vortex which propagates along ${\mathbf{B}}_0$ through the uniform plasma as a whistler mode. The observations support a prediction of force-free (J×B+neE=0) electromagnetic fields and solitary waves. Energy and helicity are approximately conserved.

Superfluorescence and amplified spontaneous emission of 29-${\mathrm{cm}}^{\mathrm{-}1}$ phonons are observed following inversion of the E¯${(}^2$E)-2A¯${(}^2$E) acoustic transition of ${\mathrm{Cr}}^{3+}$ in ruby. The conditions for both of these manifestations of phonon avalanches are selected via the ${\mathrm{Cr}}^{3+}$ concentration. Superfluorescence is described in terms of a pendulum equation of the acoustic Bloch vector. Rate equations of the level and phonon populations account for amplified spontaneous emission.

We propose a method of deforming a bulk diffusion couple which allows separate control of the effects on the kinetics of glass formation due to plastic flow and temperature increase. It is found that plastic flow enhances, by several orders of magnitude, the interdiffusion coefficient (whose temperature dependence is described by a dual-regime Arrhenius behavior) and that increasing the rate at which the load is applied results in a considerable enhancement of the process of diffusion. All these observations are tentatively ascribed to the creation of excess free volume by plastic flow.

The presence of Cu atoms in p-type Si is detected via their characteristic electric-field gradients measured at the radioactive acceptor ${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$${/}^{111}$Cd by the perturbed γγ angular correlation technique. Cu forms pairs with acceptor atoms, thereby electrically passivating them, and is present as a contamination in Si wafers. Using the experimentally known Cu diffusion data and taking into account the effect of ion pairing, a new activation energy of 0.15 eV is deduced, which is in accordance with the dissociation energy of 0.70 eV measured for Coulombic-bound-acceptor–Cu pairs.

From an interplay between scanning tunneling microscopy, surface x-ray-diffraction experiments, and theoretical predictions, an unequivocal structural model for the Cu(110)-c(6×2)O surface reconstruction is derived with ten Cu atoms within the c(6×2) unit cell, two of which form a Cu superstructure. A general picture evolves in which the present as well as the Cu(110)-(2×1)O and the Cu(100)-(2 √2 × √2 )R45°O reconstructions are stabilized by Cu-O-Cu chains directed along the [001] direction. The nucleation and growth of the c(6×2) structure occur preferentially at steps.

Korringa-Kohn-Rostoker (KKR) theory is formulated in a way that is independent of the assumption that the potential is of the muffin-tin type. The resulting form of the KKR equation retains the separation of its dependence on the lattice structure and on the potential.

Electron emission during oxidation of thin Cs films is confined to the stage ${\mathrm{Cs}}_2$${\mathrm{O}}_2$→${\mathrm{CsO}}_2$ and is caused by Auger deexcitation accompanying the (formal) reaction ${\mathrm{O}}_2^{2\mathrm{-}}$(s)+${\mathrm{O}}_2$→${2\mathrm{O}}_2^{\mathrm{-}}$(s). This nonadiabatic process becomes possible because resonance ionization of the affinity level of the impinging ${\mathrm{O}}_2$ molecule upon crossing the Fermi level ${\mathit{E}}_{\mathit{F}}$ is efficiently suppressed due to the absence of occupied states near ${\mathit{E}}_{\mathit{F}}$ at the surface.

The Pt(111)-surface ionization of hyperthermal mercury atoms (4–10 eV) was studied in helium- and hydrogen-seeded supersonic molecular beams. In spite of the large energy difference of 4.7 eV between the atomic ionization potential and the surface work function, an efficient ionization was observed. The ionization mechanism is discussed in terms of an extensive energy transfer to the surface and the creation of a transient local hot spot. Analytical applications are mentioned.

We report a numerical renormalization-group calculation of the spectral density for an electron that tunnels between two centers in a metal. The computed spectra, uniformly accurate over the parameter space, provide the first comprehensive survey of the model. Power laws at low energies and the absence of zero-energy spectral weight signal an infrared catastrophe. The renormalization of the tunneling rate by the interaction with the conduction band is discussed.

We report ab initio calculations of total energies and electronic structures of P, As, and Sb donors in GaAs and InP. In the ${\mathit{T}}_{\mathit{d}}$ geometry, all these defects exhibit two donor states in the forbidden gap: an internal optical excitation energy of the order of 1 eV, and a Franck-Condon shift of the order of 0.1 eV. All these defects possess a metastable geometry of the electrically neutral vacancy-interstitial pair with no donor states in the band gap. We discuss the differences between the six systems and explain why an optically inducible transition to the metastable state is inefficient for GaAs:${\mathrm{Sb}}_{\mathrm{Ga}}$.

The cyclotron motion of electrons in coupled-well AlGaAs/GaAs superlattices is investigated by photoluminescence of conduction band to acceptor transitions in magnetic fields up to 13 T, applied either parallel or perpendicular to the layers. For parallel fields, three different regimes are observed as the ratio of the cyclotron radius to the superlattice period is reduced, namely, tunneling cyclotron motion within the miniband, miniband breakdown, and finally a transition from electric to magnetic quantization. A fully quantum-mechanical calculation agrees well with experiment.

We report on the first observation of magnetic-domain structure during spin reversal under field in ultrathin metallic films with perpendicular anisotropy. The magnetization reversal is either dominated by the nucleation process or by domain-wall motion. The related magnetic aftereffect is analyzed starting from the Fatuzzo theory.

We have determined the Curie temperature ${\mathit{T}}_{\mathit{c}}$ of an epitaxial monolayer of Fe(110) on a W(110) substrate by means of spin-polarized low-energy-electron diffraction. Adsorption of submonolayer amount of Fe causes ${\mathit{T}}_{\mathit{c}}$ to increase distinctly. An enhancement of ${\mathit{T}}_{\mathit{c}}$ by about the same amount is also found upon adsorption of submonolayers of Pd, Ag, and ${\mathrm{O}}_2$.

The anisotropy and temperature dependence of the magnetic-field penetration in superconducting ${\mathrm{UPt}}_3$ have been measured by muon spin relaxation. The extrapolated zero-temperature values for the penetration depths parallel and perpendicular to the c axis are ${\lambda }_{\mathrm{\parallel }}$=7070±30 Å and ${\lambda }_{\mathrm{\perp }}$=7820±30 Å, respectively. The temperature dependences of ${\lambda }_{\mathrm{\parallel }}$ and ${\lambda }_{\mathrm{\perp }}$ are different and can both be accounted for by a superconducting gap function with a line of nodes in the basal plane and axial point nodes.

We study the fluctuation Ettingshausen effect in a type-II superconductor using the time-dependent Ginzburg-Landau equation. The free-fluctuation theory predicts a divergence in the Ettingshausen coefficient at T=${\mathit{T}}_{\mathit{c}2}$(H), in conflict with the recent data of Palstra et al. [Phys. Rev. Lett. 64, 3090 (1990)]. Including interactions through a self-consistent Hartree approximation eliminates the divergence and provides a quantitative explanation of the experiments.

It is shown that the parity-violated ground state of two-dimensional strongly correlated electronic systems (commensurate flux state) provides a physical realization of the anyon mechanism of superconductivity. The electromagnetic response of the commensurate flux state is calculated. It is found that the superconducting ground state is accompanied by the restoration of parity and time-reversal symmetry: the parity-violation signal is very small at low energies and momentum, and vanishes in the static limit as well as in the uniform limit.

Measurements of the field-dependent radiofrequency penetration depth λ(H,T) are used to delineate the lower-critical-field ${\mathit{H}}_{\mathit{c}1}$-T phase boundary, and to study flux dynamics in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{y}}$ crystals. For both H∥c^ and H⊥c^ ${\mathit{H}}_{\mathit{c}1}$ obeys a BCS temperature dependence with a temperature-independent anisotropy of 3.4±0.3. In the mixed state, the data obey ${\lambda }^2$(H)=[${\mathrm{\phi }}_0$/${\mathrm{\mu }}_0$α(T)]B(H), and yield both the functional dependence B(H) and the pinning force constant α(T). The latter is anisotropic, obeys an approximately (1-${\mathit{t}}^2$${)}^2$ temperature dependence, and vanishes slightly below the bulk transition temperature.

We study an interacting one-dimensional quantum lattice gas, based on the Heisenberg-Ising ring. The particles are given a charge, and the ring is threaded by a magnetic flux. We then calculate exactly the energy of the state, which begins as the ground state with zero magnetic flux, when the magnetic flux is adiabatically increased. We find the result that the period of the ground state is two flux quanta, which can be interpreted as charge carriers with half-integer charge.

A Bell inequality is derived for a state of n spin-1/2 particles which superposes two macroscopically distinct states. Quantum mechanics violates this inequality by an amount that grows exponentially with n.

Differential and absolute cross sections for the reaction p(γ,${\mathrm{\pi }}^0$) have been measured with energy-defined photons in the threshold region (${\mathit{E}}_{\gamma }$=131.4–157.2 MeV). The ${\mathit{E}}_{0+}$ amplitude has been extracted out of the data. The values found are in disagreement with predictions of low-energy theorems.