We report on shelled bubbles that can be manipulated with magnetic fields. The magnetic shell consists of self-assembled magnetic nanoparticles. The magnetic susceptibility of the bubbles is proportional to the surface area, ${\chi }_b=(9\pm 3\times {10}^{-6}\mathrm{m})r^2$ where $r$ is the radius. Magnetic bubbles are compressible in moderate acoustic fields. A bubble with a radius of $121\mu \mathrm{m}$ oscillates in resonance in a sound field of 27 kHz with a peak-to-peak radial amplitude of $1.7\mu \mathrm{m}$. The bubble oscillations induce a microstreaming flow with a toroidal vortex at the upper pole of the bubble. Further findings are the longevity of the magnetic bubbles and the ease of manipulation with standard magnets.

We present a search for a Higgs boson decaying to two $W$ bosons in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ center-of-mass energy. The data sample corresponds to an integrated luminosity of $3.0{\mathrm{fb}}^{-1}$ collected with the CDF II detector. We find no evidence for production of a Higgs boson with mass between 110 and $200\mathrm{GeV}/c^2$, and determine upper limits on the production cross section. For the mass of $160\mathrm{GeV}/c^2$, where the analysis is most sensitive, the observed (expected) limit is 0.7 pb (0.9 pb) at 95% Bayesian credibility level which is 1.7 (2.2) times the standard model cross section.

We experimentally demonstrate a chiral metamaterial exhibiting negative refractive index at terahertz frequencies. The presence of strong chirality in the terahertz metamaterial lifts the degeneracy for the two circularly polarized waves and allows for the achievement of negative refractive index without requiring simultaneously negative permittivity and negative permeability. The realization of terahertz chiral negative index metamaterials offers opportunities for investigation of their novel electromagnetic properties, such as negative refraction and negative reflection, as well as important terahertz device applications.

Here, we report the synthesis of cubic ${\mathrm{BC}}_5$ ($\mathrm{c}\mathrm{\text{−}}{\mathrm{BC}}_5$), the diamondlike B-C phase with the highest boron content ever achieved, at 24 GPa and about 2200 K, using both a laser-heated diamond anvil cell and large-volume multianvil apparatus. The synthesized phase is low compressible (bulk modulus of 335 GPa), conductive, and exhibits extreme Vickers hardness (71 GPa), unusually high for superhard materials fracture toughness ($9.5\mathrm{MPa}{\mathrm{m}}^{0.5}$), and high thermal stability (up to 1900 K); this makes it an exceptional superabrasive and promising material for high-temperature electronics.

We report results from the Cryogenic Dark Matter Search at the Soudan Underground Laboratory (CDMS II) featuring the full complement of 30 detectors. A blind analysis of data taken between October 2006 and July 2007 sets an upper limit on the weakly interacting massive particle (WIMP) nucleon spin-independent cross section of $6.6\times {10}^{-44}{\mathrm{cm}}^2$ ($4.6\times {10}^{-44}{\mathrm{cm}}^2$ when combined with previous CDMS II data) at the 90% confidence level for a WIMP mass of $60\mathrm{GeV}/c^2$. This achieves the best sensitivity for dark matter WIMPs with masses above $44\mathrm{GeV}/c^2$, and significantly restricts the parameter space for some favored supersymmetric models.

We report an inelastic neutron scattering investigation of the quantum dynamics of hydrogen molecules trapped inside anisotropic fullerene cages. Transitions among the manifold of quantized rotational and translational states are directly observed. The spectra recorded as a function of energy and momentum transfer are interpreted in terms of the rotational potential and the cage dimensions. The thermodynamics of orthohydrogen and parahydrogen are investigated through temperature dependence measurements.

Edge structures of thermally treated graphite have been studied by means of atomically resolved high-resolution TEM. The method for the determination of a monolayer or more than one layer graphene sheets is established. A series of tilting experiments proves that the zigzag and armchair edges are mostly closed between adjacent graphene layers, and the number of dangling bonds is therefore minimized. Surprisingly bilayer graphene often exhibits $AA$ stacking and is very hard to distinguish from a single graphene layer. Open edge structures with carbon dangling bonds can be found only in a local area where the closed (folding) edge is partially broken.

In ab initio theory, defects are routinely modeled by supercells with periodic boundary conditions. Unfortunately, the supercell approximation introduces artificial interactions between charged defects. Despite numerous attempts, a general scheme to correct for these is not yet available. We propose a new and computationally efficient method that overcomes limitations of previous schemes and is based on a rigorous analysis of electrostatics in dielectric media. Its reliability and rapid convergence with respect to cell size is demonstrated for charged vacancies in diamond and GaAs.

Coherent x-ray diffraction microscopy is a lensless phase-contrast imaging technique with high image contrast. Although electron tomography allows intensive study of the three-dimensional structure of cellular organelles, it has inherent difficulty with thick objects. X rays have the unique benefit of allowing noninvasive analysis of thicker objects and high spatial resolution. We observed an unstained human chromosome using coherent x-ray diffraction. The reconstructed images in two or three dimensions show an axial structure, which has not been observed under unstained conditions.

We investigate the equidistribution of the eigenfunctions on quantum graphs in the high-energy limit. Our main result is an estimate of the deviations from equidistribution for large well-connected graphs. We use an exact field-theoretic expression in terms of a variant of the supersymmetric nonlinear $\sigma$ model. Our estimate is based on a saddle-point analysis of this expression and leads to a criterion for when equidistribution emerges asymptotically in the limit of large graphs. Our theory predicts a rate of convergence that is a significant refinement of previous estimates, long assumed to be valid for quantum chaotic systems, agreeing with them in some situations but not all. We discuss specific examples for which the theory is tested numerically.

A study of solar-wind hydrogen and helium temperature observations collected by the Wind spacecraft offers compelling evidence of heating by an Alfvén-cyclotron dissipation mechanism. Observations are sorted by the rate of Coulomb interactions, or collisional age, in the plasma and the differential flow between the two species. We show that helium is preferentially heated perpendicular to the magnetic field direction by more than a factor of 6 when the flow between the species is small relative to the Alfvén wave speed and collisions are infrequent. These signatures are consistent with predictions of dissipation in the presence of multiple ion species. We also report an unexpected result: observations of efficient heating of helium parallel to the magnetic field for large differential flow relative to the sound speed.

We report x-ray magnetic circular dichroism and superconducting quantum interference device magnetometry experiments to study magnetic order and coupling in thin $\mathrm{Fe}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}(100)$ films. We observe induced magnetic order in the $(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ layer that extends over more than 2 nm, even at room temperature. We find spectroscopic evidences of a hybridized $d$ configuration of Mn atoms in $\mathrm{Fe}/(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$, with negligible Mn diffusion and/or MnFe intermixing. We show by experiment as well as by theory that the magnetic moment of the Mn ions couples antiparallel to the moment of the Fe overlayer.

The idea that we live near the center of a large, nonlinear void has attracted attention recently as an alternative to dark energy or modified gravity. We show that an appropriate void profile can fit both the latest cosmic microwave background and supernova data. However, this requires either a fine-tuned primordial spectrum or a Hubble rate so low as to rule these models out. We also show that measurements of the radial baryon acoustic scale can provide very strong constraints. Our results present a serious challenge to void models of acceleration.

A claim for evidence of dark matter interactions in the DAMA experiment has been recently reinforced. We employ a new type of germanium detector to conclusively rule out a standard isothermal galactic halo of weakly interacting massive particles as the explanation for the annual modulation effect leading to the claim. Bounds are similarly imposed on a suggestion that dark pseudoscalars might lead to the effect. We describe the sensitivity to light dark matter particles achievable with our device, in particular, to next-to-minimal supersymmetric model candidates.

Parametrization of a molecular two-electron reduced density matrix (2-RDM) enables energies and properties to be directly computed at a highly efficient computational cost. In this Letter an improved 2-RDM parametrization yields energies and properties that are markedly better than those calculated with a similar computational scaling by traditional ab initio methods. Computed 2-RDMs very nearly satisfy well-known $N$-representability conditions. Applications are made to ground-state energies of several molecules and equilibrium bond distances and harmonic frequencies of HF, ${\mathrm{F}}_2$, and CO. The method for single-bond breaking in HF and ${\mathrm{CH}}_4$ yields similar accuracy at equilibrium and nonequilibrium geometries.

We realize experimentally an atom-optics quantum-chaotic system, the quasiperiodic kicked rotor, which is equivalent to a 3D disordered system that allows us to demonstrate the Anderson metal-insulator transition. Sensitive measurements of the atomic wave function and the use of finite-size scaling techniques make it possible to extract both the critical parameters and the critical exponent of the transition, the latter being in good agreement with the value obtained in numerical simulations of the 3D Anderson model.

Using scanning tunneling spectroscopy in an ultrahigh vacuum at low temperature ($T=0.3\mathrm{K}$) and high magnetic fields ($B\le 12\mathrm{T}$), we directly probe electronic wave functions across an integer quantum Hall transition. In accordance with theoretical predictions, we observe the evolution from localized drift states in the insulating phases to branched extended drift states at the quantum critical point. The observed microscopic behavior close to the extended state indicates points of localized quantum tunneling, which are considered to be decisive for a quantitative description of the transition.

We report the observation of wave turbulence on the surface of a ferrofluid mechanically forced and submitted to a static normal magnetic field. We show that magnetic surface waves arise only above a critical field. The power spectrum of their amplitudes displays a frequency-power law leading to the observation of a magnetic wave turbulence regime which is experimentally shown to involve a 4-wave interaction process. The existence of the regimes of gravity, magnetic and capillary wave turbulence is reported in the phase space parameters as well as a triple point of coexistence of these three regimes. Most of these features are understood using dimensional analysis or the dispersion relation of the ferrohydrodynamic surface waves.

It is experimentally shown that the critical current for onset of spin torque instability in current-perpendicular-to-plane spin valves can be strongly increased using “synthetic-ferrimagnet” free layers of form ${\mathrm{FM}}_1/\mathrm{Ru}/{\mathrm{FM}}_2$ ($\mathrm{FM}=\mathrm{\text{ferrromagnet}}$). However, this increase occurs for only one polarity of bias current. A two-macrospin model is shown to reproduce the observations. The model suggests that this phenomenon is related to a polarity-dependent, spin torque-induced coresonance between the two natural dynamic modes of the ${\mathrm{FM}}_1/{\mathrm{FM}}_2$ couple. The coresonance condition facilitates energy transfer out of the spin-torque destabilized mode into the other stable mode whose effective damping (or line width) is strongly enhanced by spin torques.

A novel doubly chiral magnetic order is found in the structurally chiral langasite compound ${\mathrm{Ba}}_3{\mathrm{NbFe}}_3{\mathrm{Si}}_2{\mathrm{O}}_{14}$. The magnetic moments are distributed over planar frustrated triangular lattices of triangle units. On each of these they form the same triangular configuration. This ferrochiral arrangement is helically modulated from plane to plane. Unpolarized neutron scattering on a single crystal associated with spherical neutron polarimetry proved that a single triangular chirality together with a single helicity is stabilized in an enantiopure crystal. A mean-field analysis allows us to discern the relevance on this selection of a twist in the plane to plane super-superexchange paths.