Thermal modulation spectroscopy based on a photothermal process has been applied to hydrogenated amorphous silicon (a-Si:H)–silicon carbide (a-SiC:H) multilayered structures. The temperature derivative of the absorption spectrum drastically changes from a linear to a staircase form with decreasing a-Si:H well layer thickness below 50 Å. This result suggests that three-dimensional parabolic band transition is turned into subband transitions in the a-Si:H quantum well.

We report the first direct observation of ballistic hole transport in semiconductors, via energy spectroscopy experiments. Light holes are preselected and injected via tunneling into 31-nm-thick ${\mathrm{p}}^{+}$ GaAs layers. About 10% of the injected holes have been found to travel ballistically maintaining distributions ≃35 meV wide, with a mean free path of about 14 nm. Resonances in the injection currents, resulting from quantum interference effects of the ballistic holes, are used to support the light nature of the ballistic holes.

We report theoretical as well as experimental evidence for a new class of long-wavelength acoustic film excitations which we identify as longitudinal guided acoustic phonons. Despite a coupling to propagating transverse film modes, these new modes have lifetimes comparable to that of the Rayleigh mode and are the longitudinal counterpart to the well-known Lamb or Sezawa modes, with analogous existence criteria. The properties of the new modes are discussed in detail for ZnSe films on GaAs, the material system for which we were able to observe these modes by Brillouin spectroscopy.

It is shown that the fractional angular momentum of charged particles orbiting around a magnetic flux tube would result in fractional magnetic-flux quantization. A crucial experiment to test for the fractional quantum of magnetic-flux as well as anyons is proposed and analyzed.

Using an extended version of Handscomb’s Monte Carlo method we study the spin-(1/2 quantum antiferromagnetic Heisenberg model on square lattices of various sizes. The calculated correlation length associated with antiferromagnetic order grows very rapidly as the temperature is lowered suggesting an essential singularity. Our results are consistent with those recently observed by neutron scattering done on ${\mathrm{Lo}}_2$${\mathrm{CuO}}_4$.

Measurements of the lifetime of the zero-voltage state in a single hysteretic Josephson junction show clear evidence of two different damping regimes. Results are obtained for a wide range of damping within the underdamped region because the damping resistance depends exponentially on inverse temperature as does the junction’s quasiparticle resistance. Thus a further insight is also given on the thorny problem of the damping resistance for the resistively shunted junction model.

Ballistic point contacts, defined in the two-dimensional electron gas of a GaAs-AlGaAs heterostructure, have been studied in zero magnetic field. The conductance changes in quantized steps of $e^2$/πħ when the width, controlled by a gate on top of heterojunction, is varied. Up to sixteen steps are observed when the point contact is widened from 0 to 360 nm. An explanation is proposed, which assumes quantized transverse momentum in the point-contact region.

The magnetization and the volume magnetostriction were measured up to 39 T at low temperatures in the mixed valence ${\mathrm{Yb}}_{0.38}$${\mathrm{In}}_{0.62}$${\mathrm{Cu}}_2$ and the dense Kondo ${\mathrm{Yb}}_{0.50}$${\mathrm{Ag}}_{0.50}$${\mathrm{Cu}}_2$ compounds. ${\mathrm{Yb}}_{0.38}$${\mathrm{In}}_{0.62}$${\mathrm{Cu}}_2$ shows a distinct metamagnetic transition at 33 T. A remarkable negative volume magnetostriction was observed at the transition, giving evidence of an abrupt increase in Yb valence from the mixed-valence state to the trivalent state. ${\mathrm{Yb}}_{0.50}$${\mathrm{Ag}}_{0.50}$${\mathrm{Cu}}_2$ shows an appreciable upturn of magnetization and a gradual volume shrinkage, corresponding to a gradual Yb valence change toward the trivalent state also in the dense Kondo system.

Proposed is a molecular interpretation of the strong selectivity of field-inversion electrophoresis, recently applied to the separation of long DNA fragments. The sharp transition in the mobility is associated with an antiresonance occurring when chain-length fluctuations compete with the electrophoretic drift. A theory is outlined based on biased reptation (Slater and Noolandi) and length fluctuations (Doi). Systematic preaveraging allows a simple treatment, and important features of the data are correctly accounted for.

The probability of tunneling of the magnetization in a single-domain particle through an energy barrier between easy directions is calculated for several forms of magnetic anisotropy. Estimated tunneling rates prove to be large enough for observation of the effect with the use of existing experimental techniques.

This Letter reexamines questions about the practicality of computing the exact stability domains of certain classes of pendulum systems. We display plots showing that the intertwining of neighboring domains have a self-affine truncated-fractal structure. A simple proof of the existence of diffeomorphisms from connected basins to striated basins is also presented.

Critical correlation in thermal systems, Ising spins for example, is approximately described by clusters. A cluster is defined as a randomly picked, connected region of excess up (or down) spins. Its simulation utilizes a branching-out stochastic chain which allots spins continuously, either to the cluster or to a perimeter of average composition. Results in dimensionality from 2 to 10 show the cluster geometry to be very different than in (athermal) percolation.

The coding of chaotic trajectories in Hamiltonian systems and the stochastic reflection of points on circles introduce examples of a new kind of multifractal measure, whose Hölder α ranges all the way from 0 to ∞.

It has been argued that compression of nuclear matter to somewhat higher densities may lead to the formation of stable quark matter. A plausible alternative, which leads to radically new astrophysical scenarios, is that the stability of quark matter simply represents the stability of new particles compounded of quarks. A specific example is the SU(3)-symmetric version of the α particle, composed of spin-zero pairs of each of the baryon octet (an ‘‘octet’’ particle).

It is demonstrated by explicit construction that chiral fermions induce a nonassociative electric field algebra in a two-dimensional gauge theory.

A real-time finite-temperature formalism for interacting superstrings is described. It is used to compute the tree amplitude for open superstrings at finite temperature.

Polarization-asymmetry theorems are established which provide unambiguous tests of time-reversal invariance.

We show that binary collisions among atoms can couple the fundamental mode to its second harmonic by generating polariton modes which carry phase information between random scattering events and produce a constructively interfering component of the harmonic field.

The effects of a laser beam on the dielectronic recombination (DR) of H-like ions with continuum electrons was investigated for a single-mode, circularly polarized laser with irradiance ${10}^{12}$–${10}^{17}$ W/${\mathrm{cm}}^2$ and photon energy 0.1–5.0 eV. Laser-induced increases in the value of the DR rate coefficient, up to ∼100×, were found for recombinations via the lowest-lying intermediate states, over a narrow range of the ionic charge Z, centered near Z=5. Within this range of Z, the DR rate coefficient summed over all accessible intermediate states was increased by a factor of ∼10 over its zero-field value.

Speed ratios v/Δv greater than 1000 and temperatures less than 1 mK have been achieved for the first time in a gas expansion into vacuum. The pulsed-beam source used in these experiments had an open time of 150 μsec, a nozzle diameter of 0.125 mm, and was operated with pure He gas at 294 K and pressures between 34 and 136 atm. Speed distributions for the collimated He beam were measured by time of flight. It is possible that such temperatures may be low enough to probe the low-energy limiting behavior predicted by Wigner in 1948 for the single-collision quantum dynamics of atoms and molecules.