It is shown that the scale invariant solutions of the KS and KPZ models of surface roughening are identical for dimensions d<2, but may differ for dimensions d>2 in the strong coupling limit. For d>2, these models posses two different scaling solutions, one with d-independent scaling exponents y=z=2, and the other with d-dependent nontrivial exponents. The first of these solutions is realizable in one of these models, but not the other. These conclusions are valid to all orders in renormalized perturbation theory.

We formulate the Kohn-Sham density functional theory in terms of nonorthogonal, localized orbitals. Within this formulation we introduce a simple and effective method to localize the orbitals. Our approach leads to a plane-wave-based algorithm for total energy calculations whose computational complexity is of O(N), where N is the number of electrons. This opens the way to calculations of unprecedented scale. Our method appears to be of general character and applicable in other contexts such as quantum chemical or projected quantum Monte Carlo calculations.

Magnetotransport experiments on a low-disorder electron system in an 800 Å-wide GaAs quantum well reveal a dramatic evolution from a double- to a single-layer system as the electron density is decreased or the system is made asymmetric. At an intermediate density of 9.7×${10}^{10}$ ${\mathrm{cm}}^{\mathrm{-}2}$, we observe fractional quantum Hall states at Landau level filling factors of ν=3/4, 1/2, and 1/3, with an insulating phase separating the ν=1/2 and 1/3 liquid states. Our data demonstrate that the ν=1/2 state and the insulating phase are most stable in symmetric double-layer systems with appropriate parameters while the ν=1/3 and 3/5 states have a single-layer origin.

The magnitude of the 1/f noise in indium oxide films and ZnO accumulation layers is studied as a function of static disorder. The noise level, of both systems, is much higher than in typical metals even for the diffusive regime. The correlation between noise and static disorder leads us to suggest tht incipient localization may play an important role in determining the noise characteristics of diffusive systems near an Anderson transition.

We study the Caldeira-Leggett model of a particle coupled to a heat bath moving in a periodic cosine potential. In the limit of small viscosity we obtain an integral equation for the nonlinear response of the system to a constant or a slowly oscillating field. The equation is derived by a resummation of the infinite series expansion in the strength of the cosine potential. When solved via a self-consistent approximation it gives an analytic expression for the response function. Applications to Josephson junctions driven by a low-frequency source are discussed.

Thermodynamic quantities in quasi-2D type-II superconductors exhibit characteristic scaling behavior for high fields in the critical region around ${\mathit{H}}_{\mathit{c}2}$(T). Using a nonperturbative approach to the Ginzburg-Landau free energy functional, the scaling functions for the free energy, magnetization, entropy, and specific heat are evaluated in a closed form. The experimental data for ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{Ca}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{10}$ are presented which are in agreement with the theoretical results.

We have investigated the behavior of the superconducting energy gap Δ in ultrathin films of quench condensed Bi near the superconductor-insulator (SI) transition. From electron tunneling measurements on these films, we conclude that Δ becomes very small and approaches zero at the SI transition. We studied high-sheet-resistance films with ${\mathit{T}}_{\mathit{c}0}$’s as low as 0.19 K. This is a factor of 40 lower than the low-sheet-resistance film ${\mathit{T}}_{\mathit{c}0}$ of 6.4 K.

We have measured the dynamic spin correlation function for the quasi-one-dimensional S=1 antiferromagnet NENP by inelastic magnetic neutron scattering. Long-lived excitations (ωτ>10) exist for 0.3π≤q̃≤π, and within error exhuast the total moment sum rule. The dispersion relation retains the fundamental periodicity of the spin chain, explicitly demonstrating the absence of broken translational symmetry in the ground state. The instantaneous spin correlation function follows a square-root Lorentzian for q̃≃π but deviates substantially from this form for q̃<0.8π.

Magneto-optical Kerr effect measurements have been used to investigate the orientational dependence of the magnetic anisotropy in ultrathin Ni/Co-wedge/Ni sandwiches deposited by molecular beam epitaxy on single-crystal Cu substrates. The results show a marked dependence of both the volume and interface anisotropy terms on the growth direction of the samples: [100], [110], and [111]. In addition, the (111) interface term was found to be significantly larger than existing literature values for Co/Ni multilayers. This effect is discussed in terms of the microstructure of the studied films.

Second-harmonic spectroscopy is shown to be sensitive to interfacial electronic traps, lattice relaxation and buried surface reconstruction in ZnSe/GaAs(001) heterostructures. Newly developed photomodulation-second-harmonic-generation experiments reveal that the interfacial region contains predominantly hole traps, and that the density of these traps is substantially lower for 3×1 buried surface reconstructed samples.

Electrons bound to a metal surface by the image potential are seen to persist in the presence of various adsorbates. A new two-photon photoemission spectrometer with high resolution and sensitivity permits precise measurement of adsorbate-induced changes in image state binding energy and dispersion. This provides a unique probe of electron interaction with thin dielectric films. Monolayer xenon on Ag(111) reduced the electron’s effective mass. Spectra of alkane multilayers show rich structure with layer-by-layer shifts in binding energy. Bilayers gave evidence of electron localization.

If the SU(2)×U(1) model is extended by adding a complex singlet spin-zero field and a spontaneously broken global U(1) symmetry, a Higgs scalar can decay into a pair of Goldstone bosons. This decay could dominate over the conventional decay modes into fermion-antifermion pairs. In that case, the Higgs boson may escape detection in the standard search through ${\mathit{ZZ}}^{\mathrm{*}}$H coupling and hence could be lighter than implied by the CERN LEP data. Restrictions on the Higgs boson mass and other parameters of the model are derived using the data on the standard model Higgs boson search in the mass region 10–50 GeV.

We discuss weak-vector-boson scattering, at next-to-leading order in QCD within the framework of hadronic structure functions. We use this approach to calculate the Higgs-boson production cross section via vector-boson fusion at the CERN Large Hadron Collider and the Superconducting Super Collider; we find a modest increase over the leading-order prediction. We also give expressions for the distribution of vector bosons in a proton (effective-W approximation) including O(${\mathrm{\alpha }}_{\mathit{s}}$) corrections.

The decay ${\mathrm{\tau }}^{\mathrm{-}}$→${\nu }_{\mathrm{\tau }}$${\mathrm{\pi }}^{\mathrm{-}}$${\mathrm{\pi }}^0$η has been observed for the first time using the CLEO-II detector at the Cornell Electron Storage Ring. The measured branching ratio (0.17±0.02±0.02)%, agrees with the CVC (conserved vector current) prediction based on ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$→${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$η data. Upper limits on the branching ratios for other τ decays to final states including η mesons are improved by an order of magnitude compared to previous measurements.

We analyze the quark number susceptibility at high temperature in three-dimensional QCD where the susceptibility carries nonperturbative temperature effects at next-to-leading order. Using arguments of dimensional reduction, we show that the Coulomb bound state description used recently to describe the DeTar correlators is consistent with the free quark susceptibility, and offers a nonperturbative framework for discussing next-to-leading-order effects. The relevance of our results to four-dimensional QCD at high temperature is discussed.

Spin precession of channeled particles in bent crystals has been observed for the first time. Polarized ${\mathrm{\Sigma }}^{+}$ were channeled using bent Si crystals. These crystals provided an effective magnetic field of 45 T which resulted in a measured spin precession of 60±17°. This agrees with the prediction of 62±2° using the world average of ${\mathrm{\Sigma }}^{+}$ magnetic moment measurements. This new technique gives a ${\mathrm{\Sigma }}^{+}$ magnetic moment of (2.40±0.46±0.40)${\mathrm{\mu }}_{\mathit{N}}$, where the quoted uncertainties are statistical and systematic, respectively. We see no evidence of depolarization in the channeling process.

The relativistic cascade code arc is applied to data from the experiment E814 covering projectile rapidities in Si+Pb collisions at 14.6 GeV/c per nucleon. The result is a quantitative theoretical description of the entire range of the experimental rapidity spectrum, as well as of the number and transverse energy dependence of ‘‘punchthrough’’ protons. This plus additional detailed comparisions of transverse mass distributions strongly suggest the cascade approach can be highly useful for understanding energetic ion collisions.

The photodetachment of ${\mathrm{H}}^{\mathrm{-}}$ near the H(N=4) and H(N=5) thresholds in an external electric field is studied theoretically. The recently observed photodetachment threshold shifts of Halka et al. are interpreted in terms of the shifts of the barrier heights of the hyperspherical potential curves as the electric field strength is varied. It is shown that higher members of the zero-field Feshbach resonances can emerge as field-induced shape resonances in an electric field.

We consider the deflection of a resonant two-level atom by a quantized electromagnetic field using the Jaynes-Cummings Hamiltonian. We show that a joint measurement of the atomic momentum and an appropriate field variable allows us to reconstruct the original photon statistics even for this demolition Hamiltonian. We demonstrate that the momentum distribution of atoms scattered at the nodes of the standing wave also follows the original photon statistics of the field. In this sense a recent experiment on the optical Stern-Gerlach effect [T. Sleator et al., Phys. Rev. Lett. 68, 1996 (1992)] measures the intensity fluctuations of the standing wave.

The kicked Harper model is numerically investigated. The long-time nature of the wave function dynamics and a multifractal analysis of the spectrum provide evidence for the existence of different regimes marked by different spectral types and diffusion exponents, with a phase diagram substantially different from that of the standard Harper model.