We investigate the size-dependent behavior for negative moments of current distribution in random resistor networks. With the extreme value statistics idea, we derive the explicit form of the current distribution in small-current regime. The distribution is found to be the Weibull distribution n(x)∼exp(-$x^m$), with m>1 and x==-logi/logL. $L— is the system size. Using this distribution function, we show breakdown of multifractal behavior in negative moments regime and nonoccurrence of thermodynamic phase transition.

We report ellipsometric coverage–vapor-pressure isotherm measurements for argon on graphite over the temperature range 64 to 84 K, which resolve up to eight layers. We confirm previous observations that the first-order layering transitions broaden near 67 K. However, in the fourth and higher layers, condensation again becomes sharp and apparently first order in the range between about 73 K and a new series of layer critical points near 77 K. Thus the surface roughening transition is above 77 K and the behavior near 67 K represents disordering of only the top layer of the film.

Elastic neutron diffraction is used to study the melting of multilayer argon films physisorbed on a graphite substrate. The layers are found to disorder sequentially from the outermost layer of the film toward the graphite surface with the melting of individual layers occurring gradually over a temperature range of about 10°. For films initially two or more layers thick the melting of the layer closest to the substrate occurs near 100 K. Comparisons are made with recent computer simulations and with thermodynamic measurements.

We present first systematic numerical simulation results which show a strong indication of phase transitions, in both 2+1 and 3+1 dimensions, between weak-coupling and strong-coupling regimes in a surface-growth model. A modified ballistic deposition model is used to demonstrate the transitions and the roughness scaling exponent is measured. While the transition in 3+1 dimensions confirms the prediction of the renormalization-group analysis, the one in 2+1 dimensions had not been previously anticipated and exhibits a complex critical behavior.

It is shown that in a simple model of surface dynamics of growing 3D quasicrystals, growth proceeds through the nucleation of steps whose heights $h_s$ diverse like (Δμ${)}^{\mathrm{-}1/3}$ as the growth-driving chemical-potential difference Δμ→0. This large step size leads to very low growth velocities ${\mathit{V}}_{\mathit{g}}$∝exp{-1/3[Δ${\mathrm{\mu }}_{\mathit{c}}$(T)/Δμ${]}^{4/3}$}. Δ${\mathrm{\mu }}_{\mathit{c}}$(T) defines a rounded kinetic roughening transition and is nonuniversal. For ‘‘perfect-tiling models’’ I find Δ${\mu }_c$(T)∝$T^{\mathrm{-}3/2}$ at high temperatures T, which fits recent numerical simulations, while in models with bulk phason Debye-Waller disorder, ln(Δ${\mu }_c$)∝- √T . The growing interface is algebraically rough.

Thermal hysteresis is observed in x-ray-diffraction studies of the melting and solidification of small crystalline precipitates of lead in aluminum. Reproducible superheating as well as supercooling is present in succesive heating sequences demonstrating that they are intrinsic physical phenomena. For lead precipitates of mean size 140 and 270 Å, the width of the hysteresis loop is 88 and 62 K, respectively. These results are discussed in a phenomenological context considering the lack of free surfaces.

A Bloch-wave analysis shows how a signal dependent on the electron intensity at the atom sites can be used to form an incoherent image of a crystal structure. To a good approximation the image is given by a convolution of a compositionally sensitive object function with an appropriate resolution function, and as such can be predicted and interpreted intuitively. Information on a scale below the resolution limit can be interpreted by deconvolution.

The desorption of hydrogen from alkali-promoted surfaces has been studied with electron-stimulated desorption. Excited hydrogen states are found for work functions that are larger than the binding energies of the corresponding atomic levels. This finding is in direct contrast with the conventional image shift of neutral atomic levels near surfaces and indicates that the levels are instead downshifted near the surface. Calculations of the energy shift and broadening of atomic hydrogen levels in the vicinity of a potassium atom chemisorbed on a metal surface confirms such a downshift. A model is presented that accounts for the observed formation of excited H in ESD from alkali-promoted surfaces.

Hot electrons and phonons excited in GaAs by subpicosecond laser pulses have been studied by inelastic light scattering for photoexcited electron densities varying between ${10}^{17}$ and ${10}^{19}$ ${\mathrm{cm}}^{\mathrm{-}3}$. Transient overshoot of longitudinal-optical (LO) phonon temperature above the electron temperature has been observed. This is explained by the fast production of zone-center LO phonons by hot electrons combined with slower reabsorption of the emitted phonons due to rapid cooling of Γ valley electrons by intervalley scattering.

We reinterpret the Hubbard model in terms of doubly occupied sites and empty sites with an attractive interaction U whose pairing leads to the Mott-Hubbard transition. We develop a mean-field theory for this pairing which in a triangular lattice at T=0 leads to a first-order transition from a spiral, incommensurate metal to a commensurate insulator at U≃5.27t where a charge gap (≃0.085t) opens up. We also discuss the effect of fluctuations.

We have studied the dynamics of the nonequilibrium state produced in single-crystal superconducting indium by pulsed laser irradiation using tunnel junctions. By a suitable choice of a thin metal film in intimate contact with the indium crystal, we have been able to produce a pronounced change in the time evolution of the excess quasiparticle density which indicates that the quasiparticles are trapped in the film. This effect can take place both when the film is another superconductor of lower energy gap or is a normal metal made superconducting by the proximity effect.

We present experimental data on proximity tunneling in InGaAs/InP/InGaAs heterostructures due to a Nb film which induces superconductivity into the top InGaAs layer. The proximity effect is demonstrated in tunneling measurements yielding superconducting parameters induced in the top InGaAs layer, such as the gap, Δ, the tunneling density of states, D(E), and their variations with the temperature, T. We observe a significant smearing of D(E). This is attributed to a spatial decay of the gap into the depth of the InGaAs layer. Superconductivity in InGaAs is also directly evidenced through measurements of the lateral current using a sequence of Au-Nb-Au pads on InGaAs.

We calculate the rsponse of an N×N array of resistively shunted Josephson junctions to an imposed current I=${\mathit{I}}_{\mathrm{dc}}$+${\mathit{I}}_{\mathrm{ac}}$sin(2πνt). In a transverse dc magnetic field of p/q==f flux quanta per plaquette of area, we find fractional giant Shapiro steps in the time-averaged voltage 〈V〉 at values 〈V〉=nNhν/2eq, n=1,2,3,..., in agreement with the measurements of Benz et al. At f=1/5, 2/5, and 1/3, we find additional fractional steps at 〈V〉=Nhν/(4e). A generalization of the model of Benz et al. accounts for both the fractional giant steps at p/q and the anomalous half-integer steps.

We present the first direct observation of Lorentz-force-induced dissipative flux motion and the effect of twin boundaries as pinning centers in a single crystal of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ with twin planes oriented in a single direction.

The ground-state configurations of a lattice-gas model introduced by de Fontaine, Wille, and Moss for the distribution of empty and occupied oxygen sites in the Cu-O basal plane of the high-temperature superconductor ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathrm{z}}$ are determined. It is shown rigorously that the configurations proposed earlier by Wille and de Fontaine basically exhaust the set of possible stable ground-state structures. States of partial order are excluded, except for special values of the interaction constants.

We use a renormalized mean-field theory to study competitions between the flux phase and the resonating-valence-bond d-wave states in the t-J model. The staggered (antiferromagnetic) flux phase is unstable against infinitesimal electron-pairing amplitude at all non-half fillings. This instability finally leads to a pure d-wave resonating-valence-bond state. The hole-hole repulsive Coulomb interaction tends to stabilize the flux phase.

I give a second-quantized example of infinite statistics (in which any representation of the symmetric group can occur) for identical particles and discuss the properties of the example.

The second virial coefficient ${\mathrm{B}}_2$ for a system of spin-one-half flux-carrying fermions is computed. It is found that there arise significant differences from known results for the corresponding spinless system. Apart from the existence of cusps and a restricted periodicity of ${\mathrm{B}}_2$ when viewed as a function of the flux parameter α, one obtains here the remarkable result that there exist discontinuities in ${\mathrm{B}}_2$ at all even, nonzero values of α.

Deep modifications to the current strange-star structure can occur if strange matter is not stable all the way down to zero pressure. This would be the case, for example, if some stable particle is formed at relatively low pressure and/or temperature. We show that the inclusion of a likely specific candidate particle (quark α) in the strange-matter picture leads to stellar models that present more realistic behavior in the light of current pulsar understanding.

The two-matrix-model representation of the Ising model on a random surface is solved exactly to all orders in the genus expansion. The partition function obeys a fourth-order nonlinear differential equation as a function of the string coupling constant. This equation differs from that derived for the k=3 multicritical one-matrix model, thus disproving that this model describes the Ising model. A similar equation is derived for the Yang-Lee edge singularity on a random surface, and is shown to agree with the k=3 multicritical one-matrix model.