An entirely new type of coupled surface electromagnetic mode has been observed, the existence of which depends upon a large imaginary component of the dielectric constant of a thin layer. It is a long-range mode, giving a very sharp reflectivity dip for transverse magnetic polarized radiation coupled to it using the attenuated-total-reflection technique. Because its existence relies on the presence of a highly absorbing layer it may open up new avenues for nonlinear optics experiments.

The resistivity ρ(T) of ${\mathrm{LaH}}_{\mathrm{x}}$ (2.80≤x≤2.90) was determined from Q-factor measurements at 100 K<T<700 K. Its temperature coefficient α>0 is small at T≤200 K, and ρ(T) peaks at some T between 220 and 260 K. The peak narrows with increasing x and is extremely sharp for x≥2.86. At higher temperatures the behavior of ρ(T) is consistent with variable-range hopping. It is suggested that a delocalized band of states at $E_F$, associated with the superlattice of octahedral vacancies, becomes localized and its mobility is quenched when the superlattice collapses above ∼240±20 K.

Recent infrared-absorption measurements of the vibrations of hydrogen adsorbed on W(001) have provided unambiguous evidence for electronic damping of atomic vibrations on metallic surfaces. This is a simple example of nonadiabatic coupling of a discrete state to a continuum. We describe here selection rules and other criteria for nonadiabatic electronic dampling of adsorbate vibrations and report the observation and characterization, using angle-resolved photoemission, of a surface resonance close to the Fermi level on H-saturated W(001) which satisfies these criteria.

The photoemission signal from the first atomic layer of W(110) is used to assess the nature of the interaction between the surface atoms of the metal substrate and the adsorbates Na, K, and Cs for coverages up to 1 atomic layer. Our results indicate that there is little or no charge transfer from the alkali metal to the W surface, even in the limit of low coverage. The satellite structure of the photoemission lines of the outermost p shell of the alkali metals confirms this conclusion. While contrary to the conventional picture of alkali-metal-charge donation, these findings fully support recent theoretical calculations.

Near-edge- and surface-extended-x-ray-absorption fine-structure measurements of ${\mathrm{H}}_2$S on $\mathrm{Cu}\mathrm{}\left(001\right)p(2\mathrm{}\times 2)\mathrm{S}$ have been used to make the first direct structural determination of an intermediate molecular precursor in dissociative adsorption. Our results indicate that population of these precursor states overcomes the kinetic barrier to ${\mathrm{H}}_2$S adsorption and leads to the formation of a $c(2\mathrm{}\times 2)\mathrm{S}$ structure.

We have found that the 1/f-noise magnitude of unirradiated metal-oxide-semiconductor (MOS) transistors correlates strikingly with the radiation-induced-hole trapping efficiency of the oxide ($f_{\mathrm{OT}}$). This suggests that the previously unidentified defect that causes 1/f noise in MOS transistors is linked to the radiation-induced-hole trap, the ‘‘E’ center,’’ or to a direct precursor (likely a simple oxygen vacancy) known to be present in ${\mathrm{SiO}}_2$ before irradiation. We derive a simple equation that relates the noise and $f_{\mathrm{OT}}$.

Using the many-channel approximation to Landauer’s formula and statistical scattering theory, we calculate analytically the average, G¯, and the variance, var(G), of the conductance of a disordered sample of length L, described by a microscopic random Hamiltonian, and coupled at each end to an ideally conducting lead. We show that the coupling to the leads strongly affects the behavior of G¯ and var (G) for sample sizes L≲$L_0$, where $L_0$ is a characteristic length of the order of several tens of the elastic mean free path. For L≫$L_0$, this coupling becomes unimportant.

We argue that whenever the transition between the insulating and superconducting phases of a disordered two-dimensional Fermi system at zero temperature (T=0) is continuous, the system behaves like a normal metal right at the transition; i.e., the resistance has a finite, nonzero value at T=0. This value is universal—independent of all microscopic details. These features, consistent with recent measurements on disordered films, are hypothesized to apply to other 2D transitions at T=0, such as Anderson localization with spin-orbit coupling, and the quantum Hall effect.

We report new features of the transverse magnetoresistance (MR) anisotropy in (TMTSF${)}_2$${\mathrm{ClO}}_4$ in both the metallic phase and field-induced spin-density-wave (FISDW) phases. In the metallic phase, the MR varies as Δ$R_{\mathrm{xx}}$∝$H^{\alpha }$ where α<2 and α decreases as the magnetic field is tilted from the $c^{\mathrm{*}}$ axis. In the FISDW states, there is a dramatic enhancement of the MR anomalies at the FISDW phase transitions as the magnetic field is tilted, with particular angles for stronger and weaker enhancement. This is clear experimental evidence that the FISDW phases are not simply 2D in nature.

The electronic structures of single-crystal and ceramic samples of the electron-doped superconductor ${\mathrm{Nd}}_{2\mathrm{-}\mathrm{x}}$${\mathrm{Ce}}_{\mathrm{x}}$${\mathrm{CuO}}_{4\mathrm{-}\mathrm{y}}$ with x=0 and 0.15 have been studied using resonant photoemission spectro- scopy. Comparing these spectra with previous results for ${\mathrm{La}}_{2\mathrm{-}\mathrm{x}}$${\mathrm{Sr}}_{\mathrm{x}}$${\mathrm{CuO}}_4$ shows that for both electron and hole doping the Fermi level lies at nearly the same energy, in states that fill in the x=0 insulator gap. We point out that this would occur if the states at the Fermi level obey a Luttinger-type sum rule, i.e., according to standard theory, if the metallic state is a normal Fermi liquid.

The temperature dependence of the anisotropic upper critical magnetic field, ${\mathrm{H}}_{\mathrm{c}2}$(T), has been determined resistively in antiferromagnetic ${\mathrm{Sm}}_{1.85}$${\mathrm{Ce}}_{0.15}$${\mathrm{CuO}}_{4\mathrm{-}\mathrm{y}}$ single crystals. We observe the first evidence in high-${\mathrm{T}}_{\mathrm{c}}$ copper oxides for the interaction between superconductivity and antiferromagnetic ordering of rare-earth ions; estimates of the exchange coupling J≊0.1 eV and the Ginzburg-Landau coherence lengths ${\xi }_{\mathrm{ab}}$=79 Å and ${\xi }_{\mathrm{c}}$=14.7 Å are obtained. In both ${\mathrm{Nd}}_{1.84}$${\mathrm{Ce}}_{0.16}$${\mathrm{CuO}}_{4\mathrm{-}\mathrm{y}}$ and ${\mathrm{Sm}}_{1.85}$${\mathrm{Ce}}_{0.15}$${\mathrm{CuO}}_{4\mathrm{-}\mathrm{y}}$, the ${\mathrm{H}}_{\mathrm{c}2}$ data above ${\mathrm{T}}_{\mathrm{N}}$ can be described by ${\mathit{H}}_{\mathit{c}2}$(T)/${\mathit{H}}_{\mathit{c}2}^{+}$(0)=(1-T/${\mathit{T}}_{\mathit{c}}$${)}^{1.6}$.

High-resolution electron-energy-loss spectroscopy is used to characterize the resistivity, vibrations, and electronic structure of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ and ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_8$ single crystals cleaved in ultrahigh vacuum. Cleaved surfaces show a variety of terminations with different properties. Spectroscopy on superconducting regions reveal energy gaps in the ab plane corresponding to 7.8±0.3$k_B$$T_c$. The superconducting gap in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ shows a non-BCS temperature dependence and appears to be related to a delocalized excitation near 45 meV that persists well above $T_c$.

Picosecond infrared excitation experiments on acetanilide, an α-helix protein analog, indicate that the anomalous 1650-${\mathrm{cm}}^{\mathrm{-}1}$ band which appears on cooling of acetanilide crystals persists for at least several microseconds following rapid pulsed heating. The ground-state recovery time is 15±5 psec, consistent with a conventional mode strongly coupled to the phonon bath. We therefore suggest that the unusual temperature-dependent spectroscopy of acetanilide can be accounted for by slightly nondegenerate hydrogen atom configurations in the crystal.

A periodically driven relaxation-oscillator circuit is used to study experimentally the multifractal structure of the quasiperiodic parameter set on the critical line. The experimental data provide evidence of a phase transition in the thermodynamic free energy q(τ). The experimental thermodynamics compares well with that of the sine circle map and provides strong evidence for universality in the parameter scaling at the borderline of chaos.

It is shown that for any physical system there is an infinite number of measurements which are related to one of the undecidable problems. The undecidability of the physical systems indicates that there is an infinite number of incomputable correlation functions for each physical system. These results show that there is an inherent and irreducible limitation on the knowledge of the nature of physical systems. This uncertainty principle is caused by the undecidability principle.

An experimental search for new forces coupling to nuclear isospin with a range of ≥3 m was conducted using a torsion balance driven in resonance by a set of masses configured to generate a nearly pure isospin source field. The strength of any such coupling ξ in units of gravity per atomic mass unit is found to be bounded by -2.3×${10}^{\mathrm{-}4}$≤ξ≤+2.7×${10}^{\mathrm{-}5}$, where the positive sign represents an attractive force between like isospin charges.

We propose a new scenario of baryogenesis in which baryon number is an exact symmetry of the fundamental Lagrangian. If the global U(1) symmetry associated with baryon number is spontaneously broken at early times (when the temperature was of order 1–100 GeV) then the out-of-equilibrium decay of baryonic scalar particles can yield a cosmic baryon asymmetry in ordinary matter. This baryon number is exactly compensated by antibaryon number in the vacuum. At low temperatures, the symmetry is restored, and the antibaryons show up as neutral (antibaryonic) scalar particles or as nontopological solitons.

The gravitational field of a global monopole, recently found by Barriola and Vilenkin, is used to constrain the number density of global monopoles present in the Universe today. Requiring that the mass density in such monopoles should not greatly exceed the critical density implies that there is at most one global monopole in the local group of galaxies. Equally stringent bounds are also derived which do not depend on cosmological assumptions, using the large tidal gravitational forces associated with such monopoles.

The production rate of charged $D^{\mathrm{*}}$ mesons in jets has been measured in 1.8-TeV p¯p collisions at the Fermilab Tevatron with the Collider Detector at Fermilab. In a sample of approximately 32 300 jets with a mean transverse energy of 47 GeV obtained from an exposure of 21.1 ${\mathrm{nb}}^{\mathrm{-}1}$, a signal corresponding to 25.0±7.5(stat)±2.0(syst) $D^{\mathrm{*}\pm }$→$K^{\mp }$${\pi }^{\pm }$${\pi }^{\pm }$ events is seen above background. This corresponds to a ratio N($D^{\mathrm{*}+}$+$D^{\mathrm{*}\mathrm{-}}$)/N(jet) =0.10±0.03±0.03 for $D^{\mathrm{*}}$ mesons with fractional momentum z greater than 0.1.

A model is proposed which predicts that $m_t$ is large, that one family (e, u, and d) has only radiatively generated—and hence small—masses, and that at the unification scale $m_{\tau }^0$≃$m_b^0$ but $m_{\mu }^0$≠$m_s^0$ and $m_e^0$≠$m_d^0$. An essential feature of the model is a close connection between the pattern of breaking of unified gauge symmetry at large scales and the pattern of fermion masses at low scales, which gives a group-theoretical understanding of many features of the quark and lepton masses.