Crystalline confined systems of charges exhibit structural phase transitions as a function of the anisotropy of the confining potential. A theory which describes these structural transitions is presented. The theory is based on the transitions which occur in infinite homogeneous 1D and 2D systems. These transitions have been previously explored for 1D systems but not for 2D systems. The charge density in the inhomogeneous crystal is found using a fluid theory as well as a theory which keeps correlations in the local density approximation.

It is proposed to describe blue phases by two order parameters: the standard alignment tensor field ${\mathit{Q}}_{\mathrm{\alpha }\mathrm{\beta }}$(r) and a bond orientational tensor order parameter of octahedral point group symmetry scrO(432). The yet mysterious blue fog then emerges as a liquid of purely cubic bond orientational order. In the transition from the cubic blue phases to the blue fog the cubic space group symmetry is being reduced to its octahedral factor group. Because of the new order parameter the ${\mathit{scrO}}^5$(scrI432) structure, which in all previous calculations proved most stable, but never has been detected in experiment, is eliminated from the phase diagram.

We have investigated the viscosity η of liquid ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He mixtures at 1≤T≤100 mK and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ concentrations 0.98%≤x≤9.5%. We report on the first measurements of its pressure dependence at 0≤p≤20 bars. At 3≤T≤10 mK, the T dependence of η agrees with the Landau Fermi-liquid theory at all investigated x and p. Our results agree with calculations using quasiparticle interaction potentials V(k) derived from solubility measurements, but they disagree with predictions from pseudopotential theory. In the ballistic regime of the mixtures the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ component remains in the normal fluid state to 0.13 mK.

We introduce a model to calculate the equilibrium configuration of the interface between two monolayers of large, planar organic molecules bonded by van der Waals (vdW) forces. The model significantly simplifies analysis by replacing the conventional atom-atom vdW potential summation with a single ellipsoidal potential centered in the molecular plane. Our results indicate that recent observations of crystalline ‘‘quasiepitaxial’’ vacuum growth of incommensurate lattices of these planar molecular films result from the relative intralayer stiffness as compared to the small interlayer shear stress. The model can be used to predict molecular structures which are likely to form quasiepitaxial layers.

We study a ballistic deposition model in 1+1 dimensions in which the incident angles (the angles between the incident trajectories and the substrate) of incoming particles and randomly distributed in the range [θ,π-θ]. We find a sharp morphological transition at a critical angle ${\mathrm{\theta }}_{\mathit{c}}$≊10 °. For θ>${\mathrm{\theta }}_{\mathit{c}}$, the scaling properties of the interface are described by the Kardar-Parisi-Zhang equation. For θ<${\mathrm{\theta }}_{\mathit{c}}$, the shadowing effect leads to a very different morphology. We determine the scaling properties of this new universality class numerically and analytically.

Results of a high resolution x-ray reflectivity study of growth morphology and ordering of thin liquid-crystal films on flat glass substrate are reported. An adsorbed bilayer of crystalline order, under three dimensional clusters, was found to persist well beyond the nematic to isotropic transition. This adsorbed layer appears to be related to the surface memory effects in liquid-crystal devices. The morphology of these films can be described by the Stranski-Krastanov growth mode.

We present a stochastic method able to deal with complex Hermitian Hamiltonians where time reversal invariance is broken explicitly. We fix the phase of the wave function and show that the equation for the modulus can be solved by quantum Monte Carlo techniques. Then, any choice for its phase provides a variational upper bound for the ground state energy of the system. We apply the fixed-phase method to the 2D electron gas in the presence of a magnetic field with generalized periodic boundary conditions, where we study the transition between an incompressible ν=1/m Laughlin liquid and a Wigner crystal.

The near-${\mathit{E}}_{\mathit{F}}$ electronic structure and Fermi surface of ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_{8+\mathrm{\delta }}$ have been mapped out with angle-resolved photoemission. Key features of the measured band structure are (1) an extended region of flat ${\mathrm{CuO}}_2$ derived bands very near ${\mathit{E}}_{\mathit{F}}$ and (2) a strong propensity for Fermi surface nesting. Comparative analysis of these data with those from other cuprate superconductors suggests that these features may be responsible for many of the anomalous physical properties of the p-type cuprates, while the absence of these features may be related to the more ‘‘normal’’ physical properties of the n types.

The free induction decay signal from excitons in a ${\mathrm{ZnP}}_2$ single crystal shows an unexpected temporal evolution, polariton beat, and coherent dip. We show that the effects come from a nonzero thickness of the sample and nonzero time width of the excitation pulses. A systematic numerical calculation provides good qualitative agreement with the data. These effects are very important in understanding the experimental results which deal with the coherent interaction between excitons and optical fields.

In this paper, we present the exact solution (in the thermodynamic limit) to a one-dimensional, two-component, quantum many-body system in which like particles interact with a pair potential s(s+1)/${\sinh }^2$(r), while unlike particles interact with a pair potential -s(s+1)/${\cosh }^2$(r). We first give a proof of integrability, then derive the coupled equations determining the complete spectrum. All singularities occur in the ground state when there are equal numbers of the two components; we give explicit results for the ground state and low-lying states in this case.

We report a first-principles comparison between quasiparticle (QP) theory and density-functional theory (DFT) at a jellium surface. Once long-range Coulomb correlations—which are outside the local-density approximation—are incorporated into DFT through the exchange-correlation potential, the same yields wave functions and energy eigenvalues which are excellent approximations to their QP image-state counterparts. By contrast, our results for the electron self-energy near the surface do not support the use of local potentials for the description of excited-state damping.

Using density-functional theory we investigate the electron-lattice coupling of Ga dangling bonds at GaAs(110)/Na and GaAs(110)/K. We find that the electron capture at the bond causes a significant local surface unrelaxation. The lattice distortion even overcompensates the electron-electron repulsion, leading to the formation of a two-electron bound state (surface bipolaron), which manifests the negative-U behavior of the Ga orbital. The electron pairing favors the clustering of adatoms. The influence of the pairing on scanning tunneling microscope images and surface core-level spectra is discussed.

Spin polarized photoemission is used to examine the spin polarization of the quantum well states observed in copper films grown on a fcc Co(001) substrate. The states are observed to predominantly carry minority spin polarization and this is shown through comparison with calculation to reflect a preferential hybridization in the interface. The calculation also provides evidence that the quantum well states observed in the experiments are not only sp derived but also reflect the hybridization with the more localized copper d bands.

By spin resolved photoemission we have detected exchange-split spin-polarized electronic states in a nonmagnetic material deposited on a magnetic substrate. Epitaxial Cu overlayers on fcc Co(100) exhibit sp symmetry electronic states which are spin polarized by the confining magnetic interface. These spin-polarized states can be observed up to a film thickness of at least 10 atomic layers. The spectral polarization and intensity at the Fermi level display a periodicity correlated with the oscillations of the long range coupling between magnetic films separated by Cu(100) layers.

We introduce and calculate the work function ${\mathrm{\Phi }}_{2\mathrm{D}\mathrm{E}\mathrm{G}}$ of a 2-dimensional electron gas (2DEG). In contrast to the situation in 3D metals ${\mathrm{\Phi }}_{2\mathrm{D}\mathrm{E}\mathrm{G}}$ is determined by the image tail of the potential, which arises due to the screening by the free carriers in the 2DEG. The work function ${\mathrm{\Phi }}_{2\mathrm{D}\mathrm{E}\mathrm{G}}$ can be measured by the photoelectric effect in the far-infrared regime using existing experimental structures and techniques. Typical values for GaAs/AlGaAs heterojunctions are in the range ${\mathrm{\Phi }}_{2\mathrm{D}\mathrm{E}\mathrm{G}}$≊1.5–2 meV.

We propose a unified magnetic phase diagram of the cuprate superconductors. A new feature of this phase diagram is a broad intermediate doping region of quantum-critical, z=1, behavior, characterized by temperature independent ${\mathit{T}}_1$T/${\mathit{T}}_{2\mathit{G}}$ and linear ${\mathit{T}}_1$T, where the high energy spin waves are not overdamped. The spin gap in the moderately doped materials is related to the suppression of the spectral weight for frequencies smaller than ${\mathrm{\Delta }}_{\xi }$=c/ξ in the quantum disordered, z=1, regime. The crossover to the z=2 regime, where ${\mathit{T}}_1$T/${\mathit{T}}_{2\mathit{G}}^2$≃const, occurs only in the fully doped materials.

Time dependent fluctuations of the fraction of normal-conducting part in random resistor-superconductor (RS) and resistor-insulator (RI) networks lead to a novel effect close to the percolation threshold. The normalized noise scales as a function of the resistance with a characteristic exponent λ. The value of λ is different from the value found in classical percolation models but can be related to the resistivity exponent s (t) of the RS (RI) transition by a simple scaling relation: λ=2/s (2/t). Results of recent experiments on high-${\mathit{T}}_{\mathit{c}}$ superconducting thin films are interpreted in terms of this new effect and a crossover from three to two dimensional percolation behavior is found.

The theory of flux-line motion and ac response of a thin superconducting strip or circular disk in perpendicular time-dependent magnetic field is given. Flux dynamics in general is governed by a complex nonlinear sheet resistivity ρ/d (d is the thickness). In contrast to longitudinal fields, perpendicular field changes do not obey a diffusion equation but an integral equation with singular kernel. Screening currents immediately penetrate to the strip center and at times t≫${\mathrm{\tau }}_0$ decay as exp(-t/${\mathrm{\tau }}_0$) with ${\mathrm{\tau }}_0$=0.249ad${\mathrm{\mu }}_0$/ρ (2a is the strip width). Maximum ac losses occur at ω${\mathrm{\tau }}_0$=1.11.

We report on joint conduction noise and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ NMR measurements in the sliding spin-density wave (SDW) state of (TMTSF${)}_2$${\mathrm{PF}}_6$, where TMTSF is tetramethyltetraselenafulvalene. The noise distribution is narrow and scales linearly with current. Narrowing of the NMR line was observed simultaneously. The comparison of these two sets of data shows that the sliding motion is highly coherent and that the conduction noise frequency is equal to the winding rate of the SDW. In the depinned volume, a substantial fraction of the conduction electrons participate in the sliding mode. Consequences on the origin of conduction noise and on other transport measurements are discussed.

We have measured the specific heat, C, of the easy-axis triangular lattice antiferromagnet ${\mathrm{CsNiCl}}_3$ in order to investigate the critical behavior associated with a multicritical point when the chiral symmetry is induced by an external magnetic field B. Critical exponents α determined from C are close to zero for two successive zero-field transitions, while α=0.25±0.08 near the multicritical point at ${\mathit{T}}_{\mathit{M}}$≊4.48 K and ${\mathit{B}}_{\mathit{M}}$≊2.25 T, and α=0.37±0.08 at the high-field phase boundary (B=6 T) far away from ${\mathit{B}}_{\mathit{M}}$. The observed crossover from ordinary XY behavior for B<${\mathit{B}}_{\mathit{M}}$ to n=3 chiral behavior at ${\mathit{B}}_{\mathit{M}}$ and finally to n=2 chiral behavior for B≫${\mathit{B}}_{\mathit{M}}$ is in very good agreement with recent theoretical predictions.