We report on the $g$-factor measurement of the first isomeric state in ${}_{16}{}^{43}\mathrm{S}_{27}$ [$E_x=320.5(5)\mathrm{keV}$, $T_{1/2}=415(5)\mathrm{ns}$, and $g=0.317(4)$]. The $7/2^{-}$ spin-parity of the isomer and the intruder nature of the ground state of the nucleus are experimentally established for the first time, providing direct and unambiguous evidence of the collapse of the $N=28$ shell closure in neutron-rich nuclei. The shell model, beyond the mean-field and semiempirical calculations, provides a very consistent description of this nucleus showing that a well deformed prolate and quasispherical states coexist at low energy.

Based on the concept of complementary media, we propose an invisibility cloak operating at a finite frequency that can cloak an object with a prespecified shape and size within a certain distance outside the shell. The cloak is comprised of a dielectric core and an “antiobject” embedded inside a negative index shell. The cloaked object is not blinded by the cloaking shell since it lies outside the cloak. Full-wave simulations in two dimensions have been performed to verify the cloaking effect.

Using a highly coherent focused electron probe in a fifth-order aberration-corrected transmission electron microscope, we report on resolving a crystal spacing less than 50 pm. Based on the geometrical source size and residual coherent and incoherent axial lens aberrations, an electron probe is calculated, which is theoretically capable of resolving an ideal 47 pm spacing with 29% contrast. Our experimental data show the 47 pm spacing of a Ge $⟨114⟩$ crystal imaged with 11%–18% contrast at a 60%–95% confidence level, providing the first direct evidence for sub-50-pm resolution in annular dark-field scanning transmission electron microscopy imaging.

The (114) surface of the semimetal Bi is found to support a quasi-one-dimensional, metallic surface state. As required by symmetry, the state is degenerate along the $\overline{\Gamma }-\overline{Y}$ line of the surface Brillouin zone with a highest binding energy of $\approx 150\mathrm{meV}$. In the $\overline{\Gamma }-\overline{X}$ direction the degeneracy is lifted by the strong spin-orbit splitting in Bi, as directly shown by spin-resolved photoemission. This results in a Fermi contour consisting of two closely separated, parallel lines of opposite spin direction. It is argued that similar states on related insulators would give rise to a one-dimensional quantum spin Hall effect.

We have studied friction and dissipation in single and bilayer graphene films grown epitaxially on SiC. The friction on SiC is greatly reduced by a single layer of graphene and reduced by another factor of 2 on bilayer graphene. The friction contrast between single and bilayer graphene arises from a dramatic difference in electron-phonon coupling, which we discovered by means of angle-resolved photoemission spectroscopy. Bilayer graphene as a lubricant outperforms even graphite due to reduced adhesion.

We demonstrate nuclear double resonance for nanometer-scale volumes of spins where random fluctuations rather than Boltzmann polarization dominate. When the Hartmann-Hahn condition is met in a cross-polarization experiment, flip-flops occur between two species of spins and their fluctuations become coupled. We use magnetic resonance force microscopy to measure this effect between ${}^1\mathrm{H}$ and ${}^{13}\mathrm{C}$ spins in ${}^{13}\mathrm{C}$-enriched stearic acid. The development of a cross-polarization technique for statistical ensembles adds an important tool for generating chemical contrast in nanometer-scale magnetic resonance.

The dynamical onset of lane formation is studied in experiments with binary complex plasmas under microgravity conditions. Small microparticles are driven and penetrate into a cloud of big particles, revealing a strong tendency towards lane formation. The observed time-resolved lane-formation process is in good agreement with computer simulations of a binary Yukawa model with Langevin dynamics. The laning is quantified in terms of the anisotropic scaling index, leading to a universal order parameter for driven systems.

We propose an extension of the Landau-Lifshitz-Gilbert (LLG) equation by explicitly including the role of conduction electrons in magnetization dynamics of conducting ferromagnets. The temporal and spatial dependent magnetization order parameter $\mathbf{m}(\mathbf{r},t)$ generates both electrical and spin currents that provide dissipation of the energy and angular momentum of the processing magnet. The resulting LLG equation contains highly spatial dependence of damping term and thus micromagnetic simulations based on the standard LLG equation should be reexamined for magnetization dynamics involving narrow domain walls and spin waves with short wavelengths.

Heat transport in the quantum Hall regime is investigated using micron-scale heaters and thermometers positioned along the edge of a millimeter-scale two dimensional electron system (2DES). The heaters rely on localized current injection into the 2DES, while the thermometers are based on the thermoelectric effect. In the $\nu =1$ integer quantized Hall state, a thermoelectric signal appears at an edge thermometer only when it is “downstream,” in the sense of electronic edge transport, from the heater. When the distance between the heater and the thermometer is increased, the thermoelectric signal is reduced, showing that the electrons cool as they propagate along the edge.

Surface enhanced Raman scattering (SERS) is studied from optically trapped dielectric spheres partially covered with silver colloids in a solution with SERS active molecules. The Raman scattering and Brownian motion of the sphere are simultaneously measured to reveal correlations between the enhancement of the Raman signal and average position of the sphere. The correlations are due to the momenta transfer of the emitted Raman photons from the probe molecules. The addition of a mechanical force measurement provides a different dimension to the study of Raman processes.

We present a numerical study of the effect of knotting on the ejection of flexible and semiflexible polymers from a spherical, viruslike capsid. The polymer ejection rate is primarily controlled by the knot, which moves to the hole in the capsid and then acts as a ratchet. Polymers with more complex knots eject more slowly and, for large knots, the knot type, and not the flexibility of the polymer, determines the rate of ejection. We discuss the relation of our results to the ejection of DNA from viral capsids and conjecture that this process has the biological advantage of unknotting the DNA before it enters a cell.

A new calculation of the $\overline{p}/p$ ratio in cosmic rays is compared to the recent PAMELA data. The good match up to 100 GeV allows us to set constraints on exotic contributions from thermal weakly interacting massive particle (WIMP) dark matter candidates. We derive stringent limits on possible enhancements of the WIMP $\overline{p}$ flux: a $m_{\mathrm{WIMP}}=100\mathrm{GeV}$ (1 TeV) signal cannot be increased by more than a factor of 6 (40) without overrunning PAMELA data. Annihilation through the $W^{+}{W}^{-}$ channel is also inspected and cross-checked with $e^{+}/(e^{-}+e^{+})$ data. This scenario is strongly disfavored as it fails to simultaneously reproduce positron and antiproton measurements.

Experimental data obtained using low energy electron beams are presented which show that films of ${\mathrm{N}}_2\mathrm{O}$, of several hundred monolayers (ML), spontaneously acquire a positive potential of as high as 5 V. Films do not possess a dipole double layer but for $>40\mathrm{ML}$ display a constant electric field within the material. This new phenomenon is attributed to dipole alignment. The phenomenon also shows a strong temperature dependence. This is revealed by the differing dependence of the surface potential on the film thickness at different temperatures and by electron transmission spectra which display marked structure at 62 K which is absent at 40 K.

A new compression technique, which enables the study of solids into the TPa regime, is described and used to ramp (or quasi-isentropically) compress diamond to a peak pressure of 1400 GPa. Diamond stress versus density data are reported to 800 GPa and suggest that the diamond phase is stable and has significant material strength up to at least this stress level. Data presented here are the highest ramp compression pressures by more than a factor of 5 and the highest-pressure solid equation-of-state data ever reported.

First-principles molecular dynamics simulations reveal a liquid-liquid phase transition in supercooled elemental silicon. Two phases coexist below $T_c\approx 1232\mathrm{K}$ and above $p_c\approx -12\mathrm{kB}$. The low-density phase is nearly tetracoordinated, with a pseudogap at the Fermi surface, while the high-density phase is more highly coordinated and metallic in nature. The transition is observed through the formation of van der Waals loops in pressure-volume isotherms below $T_c$.

We analyze the magnetic and electronic properties of the quantum critical heavy fermion superconductor $\beta \mathrm{\text{−}}{\mathrm{YbAlB}}_4$, calculating the Fermi surface and the angular dependence of the extremal orbits relevant to the de Haas–van Alphen measurements. Using a combination of the realistic materials modeling and single-ion crystal field analysis, we are led to propose a layered Kondo lattice model for this system, in which two-dimensional boron layers are Kondo coupled via interlayer Yb moments in a $J_z=\pm 5/2$ state. This model fits the measured single-ion magnetic susceptibility and predicts a substantial change in the electronic anisotropy as the system is pressure tuned through the quantum critical point.

Spin filtering happens due to the discriminative tunneling probabilities for spin-up and spin-down electrons through a magnetic barrier and can result in highly spin polarized tunnel currents. Combining two such barriers in a tunnel junction thus leads to large magnetoresistance without the necessity of magnetic electrodes. We demonstrate the realization of such unconventional tunnel junctions using double EuS spin filter barriers with Al electrodes. The novel nonmonotonic and asymmetric bias behavior in magnetoresistance can be qualitatively modeled in the framework of WKB approximations.

Thermal diffusion of high polymers in a continuous medium is independent of the molecular weight $M_w$. Accounting for the solvent molecular structure and the Brownian motion of the solute, we derive an additional contribution of opposite sign which is significant for short chains but vanishes as $M_w\to \infty$. Our findings explain the dependence on $M_w$ observed recently for polystyrene, and its inverse Soret effect at very small $M_w$. Moreover, they bridge the gap between the macroscopic hydrodynamics description for large solutes and the enthalpy-of-transport picture for small molecules.

Experimental results of secondary electromagnetic radiation, stimulated by high-frequency radio waves irradiating the ionosphere, are reported. We have observed emission peaks, shifted in frequency up to a few tens of Hertz from radio waves transmitted at several megahertz. These emission peaks are by far the strongest spectral features of secondary radiation that have been reported. The emissions are attributed to stimulated Brillouin scattering, long predicted but hitherto never unambiguously identified in high-frequency ionospheric interaction experiments. The experiments were performed at the High-Frequency Active Auroral Research Program (HAARP), Alaska, USA.

We present an angle resolved photoemission study of ${\mathrm{V}}_2{\mathrm{O}}_3$, a prototype system for the observation of Mott transitions in correlated materials. We show that the spectral features corresponding to the quasiparticle peak in the metallic phase present a marked wave vector dependence, with a stronger intensity along the $\Gamma Z$ direction. The analysis of their intensity for different probing depths shows the existence of a characteristic length scale for the attenuation of coherent electronic excitations at the surface. This length scale, which is larger than the thickness of the surface region as normally defined for noncorrelated electronic states, is found to increase when approaching the Mott transition. These results are in agreement with the behavior of quasiparticles at surfaces as predicted by Borghi et al. [Phys. Rev. Lett. 102, 066806 (2009)].