The photon pair correlation in the laser-excited fluorescence of a single trapped and cooled ${\mathrm{Ba}}^{+}$ ion shows antibunching and, in addition, novel nonclassical phenomena absent in the fluorescence of two-level atoms. They include excessive transient values of the correlation caused by optical pumping, and temporally extended sub-Poissonian photon emission probability which arises from the transient excitation of nonabsorbing Raman coherence. The fluorescence also displays sub-Poissonian photon statistics.

A frequency-tunable source of squeezed light is employed for spectroscopic measurements of atomic cesium. Relative to the usual quantum limit associated with vacuum-state fluctuations, enhanced sensitivity is demonstrated for the detection of Doppler-free resonances in saturation spectroscopy, with an improvement of 3.1 dB directly observed and 3.8 dB inferred after correcting for detector thermal noise.

Numerical and analytic techniques are used to study the roll patterns which appear following a convective instability as modeled by the Swift-Hohenberg equation. The results of this work reveal the presence of a disordered state and a quasiordered state at large and small noise strengths, respectively. The dynamical approach to these states is shown to be rapid in the former case and slow in the later. Both numerical and analytic calculations indicate that the slow dynamics can be characterized by a simple scaling relationship.

We examine the derivation of eddy-diffusivity equations for transport of passive scalars in a turbulent velocity field. Our main contention is that, in the long-time–large-distance limit, the eddy-diffusivity equations can take very different forms according to the statistical properties of the subgrid velocity, and that these equations depend very sensitively on the interplay between spatial and temporal velocity fluctuations. Such crossovers can be represented in a ‘‘phase diagram’’ involving two relevant statistical parameters. Strikingly, the Kolmogorov-Obukhov statistical theory is shown to lie on a phase-transition boundary.

Large-scale steady-state convection is found to dominate the particle transport just inside the last closed flux surface (LCFS) in Ohmic discharges in the CCT tokamak. Near the limiter radius and in the scrape-off layer, fluctuation-induced transport is prevalent. At the L-H transition, the convection pattern near the LCFS is disrupted and a more poloidally symmetric, near-sonic plasma flow develops. Convective and turbulent particle transport are reduced across the entire edge region, resulting in the formation of the H-mode edge transport barrier.

A new quantitative representation of the generalized Kirchhoff’s law relating the emission from each propagating branch to the absorption along the corresponding branch is established, including for the first time the effects of inhomogeneous magnetic fields on cyclotron and synchrotron radiation from mode conversion theory. The concept of optical depth is revised to include effects of reflection and conversion in addition to transmission. Via the use of a variational principle, the source distribution function for the inhomogeneous emitting layer is calculated.

A series of experiments was conducted to study the surface memory effect at the liquid-crystal–polymer interface. The results show that the liquid-crystal molecules appear to have anchored at the memory-imprinted polymer surface with a rather weak azimuthal anisotropy in their orientational distribution arising from reorientation in local surface potential wells by the bulk alignment.

We performed ab initio molecular-dynamics simulations on an equimolar Si-C amorphous alloy. a-SiC is found not to exhibit chemical order and to be much complex than commonly believed. Our simulation is in good agreement with most measurements, although many interpretations of experimental data disagree with our results. The reasons for this discrepancy are analyzed and it is proposed that neutron scattering experiments can resolve the issue. Our study highlights the importance of reliable techniques complementary to experiment for a full characterization of amorphous semiconducting alloys.

We present computer simulations of kinetic growth models with a physically realistic surface diffusion process and without desorption. The results demonstrate that the asymptotic statistical scaling properties of the surface generated under these conditions are still correctly depicted by the Kardar-Parisi-Zhang (KPZ) theory. We show that surface diffusion nevertheless introduces a novel type of scaling at early times which will eventually crossover to the KPZ scaling. Furthermore, we make a clear connection between kinetic growth models and molecular-beam-epitaxy processes by illustrating the impact of surface diffusion on reducing the concentration of bulk defects.

The audio-frequency mechanical properties of oscillators fabricated from boron-doped single-crystal silicon were measured as a function of temperature. The mechanical properties (${\mathit{Q}}^{\mathrm{-}1}$ and period) are dominated by the boron impurities and cannot be attributed to glassy defects. We also found the higher strain mechanical response of these crystals to be nonlinear below 0.3 K. The strength of this nonlinearity is related to the boron concentration.

[Pt(en${)}_2$][Pt(en${)}_2$${\mathrm{Cl}}_2$](${\mathrm{ClO}}_4$${)}_4$ (en=ethylenediamine) is found to undergo a novel phase transition from the charge-density-wave (CDW) state to a new phase under hydrostatic pressure. The new phase appears at 3 GPa and coexists with the CDW state up to 6 GPa, at least. The volume ratio between the two coexisting phases measured by Raman scattering spectroscopy changes continuously with pressure. The result is discussed in terms of the theoretical approach to the polymorphic phase transition developed recently by Bassler, Sasaki, and Griffiths. It is suggested that kink solitons play an important role in this phase transition.

We analyze statistical properties of random walkers which disappear when they meet and make offsprings by a controllable rate. Numerical results for one, two, and three dimensions and for the Sierpinski gasket are assessed in a view of the mean-field theory predictions. Universality classes are found to depend on the number of offsprings in space dimension less than 3.

A model for ion transport in glass is presented which is based on the experimental evidence that cations in glass create and maintain their own characteristic environments. By postulating the existence of a site memory effect, we are able to visualize the formation of conducting pathways. We develop a quantitative theory which explains the general occurrence of the mixed cation (alkali) effect in glassy material and, in addition, shows that the anomalous dependence of conductivity on the modifier content in single alkali glasses follows a simple power-law relation.

We report measurements of heat transport from a solid substrate into a thick superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ film at sub-kelvin temperatures. We believe this transport is bottlenecked by the insufficient generation of excitations in the film capable of causing evaporation of atoms. An effective film temperature and an effective Kapitza resistance are defined. The effective Kapitza resistance is more than 3 orders of magnitude larger than for bulk helium, with an exponential temperature dependence.

We examine the metallic phase of the positionally disordered Anderson-Hubbard model as a prototype of a strongly correlated disordered metal. We find that the low-temperature thermodynamics is dominated by spin excitations in rare regions, leading to non-Fermi-liquid behavior as T→0 with a diverging susceptibility, a specific heat rising faster than T, and a vanishing spin diffusion coefficient. We argue that the results should, in principle, apply throughout the metallic phase of random alloys which undergo a transition, as a function of concentration, to an insulating phase with local moments.

We find that strong magnetic fields reduce the effectiveness of the Coulomb gap in determining the variable-range-hopping (VRH) resistivity ρ. We propose a crossover phenomenon characterized by a temperature ${\mathit{T}}_{\mathit{c}}$ with the Coulomb gap affecting the VRH resistivity only below ${\mathit{T}}_{\mathit{c}}$. The value of ${\mathit{T}}_{\mathit{c}}$ decreases as the magnetic field increases. Our theoretical model explains the observed crossover from a lnρ(H=0)∝${\mathit{T}}^{\mathrm{-}1/2}$ law to a lnρ(H)∝[${\mathit{T}}_0$(H)/T${]}^{1/3}$ law with ${\mathit{T}}_0$∝H.

We report the time-resolved circular dichroism induced by nonthermal distributions of carriers in GaAs quantum wells, separating completely, for the first time, the effects of screening and phase space filling. Thermalization of the initial excitation is strongly inhibited when carriers are laterally confined into zero dimensions by a large perpendicular magnetic field.

We report measurements of the phase-slip process by which charge-density-wave (CDW) current is converted to single-particle current at electrical contacts. An excess voltage ${\mathit{V}}_{\mathrm{ps}}$ produces a large static deformation of the CDW phase, which drives formation of dislocation loops. Measurements of the phase-slip rate as a function of the applied stress ${\mathit{V}}_{\mathrm{ps}}$ for both CDWs in ${\mathrm{NbSe}}_3$ reveal a diodelike relation, analogous to that for phase slip in superfluids. Our results are generally consistent with the predictions of Ramakrishna et al., and may have significant implications for study of CDW dynamics of temperatures well below the Peierls transition.

We observe the capacitance signal resulting from single electrons tunneling into discrete quantum levels. The electrons tunnel between a metallic layer and confined states of a single disk in a microscopic capacitor fabricated in GaAs. Charge transfer occurs only for bias voltages at which a quantum level resonates with the Fermi energy of the metallic layer. This creates a sequence of distinct capacitance peaks whose bias positions directly reflect the electronic spectrum of the confined structure. From the magnetic field evolution of the spectrum, we deduce the nature of the bound states.

We report low-temperature measurements of the frequency-dependent magnetic noise and magnetic susceptibility of nanometer-scale antiferromagnetic horse-spleen ferritin particles, using an integrated dc SQUID microsusceptometer. A sharply defined resonance near 1 MHz develops below T∼0.2 K. The behavior of this resonance as a function of temperature, applied magnetic field, and particle concentration indicates that it results from macroscopic quantum tunneling of the Néel vector of the antiferromagnets.