Polymer glasses have numerous advantageous mechanical properties in comparison to other materials. One of the most useful is the high degree of toughness that can be achieved due to significant yield occurring in the material. Remarkably, the onset of plasticity in polymeric materials is very poorly quantified, despite its importance as the ultimate limit of purely elastic behavior. Here, we report the results of a novel experiment which is extremely sensitive to the onset of yield and discuss its impact on measurement and elastic theory. In particular, we use an elastic instability to locally bend and impart a local tensile stress in a thin, glassy polystyrene film, and directly measure the resulting residual stress caused by the bending. We show that plastic failure is initiated at extremely low strains, of the order ${10}^{-3}$ for polystyrene. Not only is this critical strain found to be small in comparison to bulk measurement, we show that it is influenced by thin film confinement—leading to an increase in the critical strain for plastic failure as film thickness approaches zero.

We have used low energy electron microscopy to demonstrate how the interaction of $4,4^{\prime }$-biphenyldicarboxylic acid (BDA) molecules with (steps on) the Cu(001) surface determines the structure of supramolecular BDA networks on a mesoscopic length scale. Our in situ real time observations reveal that steps are permeable to individual molecules but that the change in crystal registry between different layers of the Cu substrate causes them to be completely impermeable to condensed BDA domains. The resulting growth instabilities determine the evolution of the domain shape and include a novel Mullins-Sekerka-type growth instability that is characterized by high growth rates along, instead of perpendicular to, the Cu steps. This growth instability is responsible for the majority of residual defects in the BDA networks.

We have investigated the structure of the ${\mathrm{Al}}_{13}{\mathrm{Fe}}_4(010)$ surface using both experimental and ab initio computational methods. The results indicate that the topmost surface layers correspond to incomplete puckered ($P$) planes present in the bulk crystal structure. The main building block of the corrugated termination consists of two adjacent pentagons of Al atoms, each centered by a protruding Fe atom. These motifs are interconnected via additional Al atoms referred to as “glue” atoms which partially desorb above 873 K. The surface structure of lower atomic density compared to the bulk $P$ plane is explained by a strong Fe-Al-Fe covalent polar interaction that preserves intact clusters at the surface. The proposed surface model with identified Fe-containing atomic ensembles could explain the ${\mathrm{Al}}_{13}{\mathrm{Fe}}_4$ catalytic properties recently reported in line with the site-isolation concept [M. Armbrüster et al., Nat. Mater. 11, 690 (2012)].

The quantum Hall state at total filling factor ${\nu }_T=1$ in bilayer systems realizes an exciton condensate and exhibits a zero-bias tunneling anomaly, similar to the Josephson effect in the presence of fluctuations. In contrast to conventional Josephson junctions, no Fraunhofer diffraction pattern has been observed, due to disorder induced topological defects, so-called merons. We consider interlayer tunneling in the presence of microwave radiation, and predict Shapiro steps in the tunneling current-voltage characteristic despite the presence of merons. Moreover, the Josephson oscillations can also be observed as resonant features in the microwave dynamical conductance.

The correlation between magnetic and structural transitions in ${\mathrm{Gd}}_5{\mathrm{Si}}_x{\mathrm{Ge}}_{4-x}$ hampers the studies of valence electron concentration (VEC) effects on magnetism. Such studies require decoupling of the VEC-driven changes in the magnetic behavior and crystal structure. The designed compounds, ${\mathrm{Gd}}_5{\mathrm{GaSb}}_3$ and ${\mathrm{Gd}}_5{\mathrm{GaBi}}_3$, adopt the same ${\mathrm{Sm}}_5{\mathrm{Ge}}_4$-type structure as ${\mathrm{Gd}}_5{\mathrm{Ge}}_4$ while the VEC increases from $31e^{-}/\mathrm{formula}$ in ${\mathrm{Gd}}_5{\mathrm{Ge}}_4$ to $33e^{-}/\mathrm{formula}$ in ${\mathrm{Gd}}_5{\mathrm{GaPn}}_3$ (Pn: pnictide atoms). As a result, the antiferromagnetic ground state in ${\mathrm{Gd}}_5{\mathrm{Ge}}_4$ is tuned into the ferromagnetic one in ${\mathrm{Gd}}_5{\mathrm{GaPn}}_3$. First-principles calculations reveal that the nature of interslab magnetic interactions is changed by introducing extra $p$ electrons into the conduction band, forming a ferromagnetic bridge between the adjacent ${}_{\propto }{}^2[{\mathrm{Gd}}_5{T}_4]$ slabs.

High degeneracy in ground states leads to the generation of exotic zero-energy modes, a representative example of which is the formation of molecular spin-liquid-like fluctuations in a frustrated magnet. Here we present single-crystal inelastic neutron scattering results for the frustrated magnet ${\mathrm{MgCr}}_2{\mathrm{O}}_4$, which show that a common set of finite-energy molecular spin excitation modes is sustained in both the liquid-like phase above magnetic ordering temperature $T_{\mathrm{N}}$ and an ordered phase with an extremely complex magnetic structure below $T_{\mathrm{N}}$. Based on this finding, we propose the concept of high degeneracy in excited states, which promotes local resonant elementary excitations. This concept is expected to have ramifications on our understanding of excitations in many complex systems, including not only spin but also atomic liquids, complex order systems, and amorphous systems.

We develop a microscopic theory of finite-temperature spin-nematic orderings in three-dimensional spatially anisotropic magnets consisting of weakly coupled frustrated spin-$\frac{1}{2}$ chains with nearest-neighbor and next-nearest-neighbor couplings in a magnetic field. Combining a field theoretical technique with density-matrix renormalization group results, we complete finite-temperature phase diagrams in a wide magnetic-field range that possess spin-bond-nematic and incommensurate spin-density-wave ordered phases. The effects of a four-spin interaction are also studied. The relevance of our results to quasi-one-dimensional edge-shared cuprate magnets such as ${\mathrm{LiCuVO}}_4$ is discussed.

We report on detailed polarized small-angle neutron scattering on cubic FeGe in magnetic fields applied either along (transverse) the scattering vector or parallel (longitudinal) to the neutron beam. The ($H$, $T$) phase diagrams for all principal axes contain a segmented $A$-phase region just below the onset of magnetic order. Hexagonal Bragg-spot patterns were observed across the entire $A$-phase region for the longitudinal geometry. Scattering intensity was observed in parts of the $A$ phase for both scattering configurations. Only in a distinct pocket ($A_1$) was vanishing scattering intensity found in the transverse geometry.

We show that actin lamellar fragments driven solely by polymerization forces at the bounding membrane are generically motile when the circular symmetry is spontaneously broken, with no need of molecular motors or global polarization. We base our study on a nonlinear analysis of a recently introduced minimal model [Callan-Jones et al., Phys. Rev. Lett. 100, 258106 (2008)]. We prove the nonlinear instability of the center of mass and find an exact and simple relation between shape and center-of-mass velocity. A complex subcritical bifurcation scenario into traveling solutions is unfolded, where finite velocities appear through a nonadiabatic mechanism. Examples of traveling solutions and their stability are studied numerically.

We investigate the rheological characteristics of human blood plasma in shear and elongational flows. While we can confirm a Newtonian behavior in shear flow within experimental resolution, we find a viscoelastic behavior of blood plasma in the pure extensional flow of a capillary breakup rheometer. The influence of the viscoelasticity of blood plasma on capillary blood flow is tested in a microfluidic device with a contraction-expansion geometry. Differential pressure measurements revealed that the plasma has a pronounced flow resistance compared to that of pure water. Supplementary measurements indicate that the viscoelasticity of the plasma might even lead to viscoelastic instabilities under certain conditions. Our findings show that the viscoelastic properties of plasma should not be ignored in future studies on blood flow.

In general, a quantum measurement yields an undetermined answer and alters the system to be consistent with the measurement result. This process maps multiple initial states into a single state and thus cannot be reversed. This has important implications in quantum information processing, where errors can be interpreted as measurements. Therefore, it seems that it is impossible to correct errors in a quantum information processor, but protocols exist that are capable of eliminating them if they affect only part of the system. In this work we present the deterministic reversal of a fully projective measurement on a single particle, enabled by a quantum error-correction protocol in a trapped ion quantum information processor. We further introduce an in-sequence, single-species recooling procedure to counteract the motional heating of the ion string due to the measurement.

Different models of universes are considered in the context of teleparallel theories. Assuming that the universe is filled by a fluid with an equation of state $P=-\rho -f(\rho )$, for different teleparallel theories and different equation of state we study its dynamics. Two particular cases are studied in detail: in the first one we consider a function $f$ with two zeros (two de Sitter solutions) that mimics a huge cosmological constant at early times and a pressureless fluid at late times; in the second one, in the context of loop quantum cosmology with a small cosmological constant, we consider a pressureless fluid ($P=0\iff f(\rho )=-\rho$) which means there are de Sitter and anti–de Sitter solutions. In both cases one obtains a nonsingular universe that at early times is in an inflationary phase; after leaving this phase, it passes trough a matter dominated phase and finally at late times it expands in an accelerated way.

We propose a tunable resonant sensor to detect gravitational waves in the frequency range of 50–300 kHz using optically trapped and cooled dielectric microspheres or microdisks. The technique we describe can exceed the sensitivity of laser-based gravitational wave observatories in this frequency range, using an instrument of only a few percent of their size. Such a device extends the search volume for gravitational wave sources above 100 kHz by 1 to 3 orders of magnitude, and could detect monochromatic gravitational radiation from the annihilation of QCD axions in the cloud they form around stellar mass black holes within our galaxy due to the superradiance effect.

Using a classical ensemble approach, electrons detached sequentially by short circularly polarized laser pulses are predicted to be correlated in their emission directions. The correlation is introduced by the laser pulses. By changing the laser intensity, the angle between the two emissions can be controlled continuously, from 0° (parallel) to 90° (perpendicular) to 180° (antiparallel). The effect on the resultant ion momentum distribution is discussed.

Using a 45 fs pump pulse at 800 nm, a wave packet is created in a charge asymmetric dissociation channel of iodine, ${\mathrm{I}}_2^{2+}\to {\mathrm{I}}^{2+}+{\mathrm{I}}^{0+}$ (2,0). As the molecule dissociates, a two-color ($1\omega 2\omega$) probe pulse is used to study the dynamics as a function of internuclear separation $R$. We find a critical region of $R$ in which there is spatially asymmetric enhanced ionization of the (2,0) channel to a counterintuitive (1,2) channel. In this region the ${\mathrm{I}}^{0+}$ is ionized such that one electron is released to the continuum and another is transferred to the ${\mathrm{I}}^{2+}$ resulting in ${\mathrm{I}}^{0+}\to {\mathrm{I}}^{2+}$ and ${\mathrm{I}}^{2+}\to {\mathrm{I}}^{1+}$. At larger $R$, the ionization is consistent with simple one-electron ionization in a double well where ${\mathrm{I}}^{0+}\to {\mathrm{I}}^{1+}$. We find qualitative agreement between simulations and experiment further highlighting the importance of multielectron effects in the strong-field ionization of molecules.

The sensitivity of inertial confinement fusion implosions, of the type performed on the National Ignition Facility (NIF) [1], to low-mode flux asymmetries is investigated numerically. It is shown that large-amplitude, low-order mode shapes (Legendre polynomial $P_4$), resulting from low-order flux asymmetries, cause spatial variations in capsule and fuel momentum that prevent the deuterium and tritium (DT) “ice” layer from being decelerated uniformly by the hot spot pressure. This reduces the transfer of implosion kinetic energy to internal energy of the central hot spot, thus reducing the neutron yield. Furthermore, synthetic gated x-ray images of the hot spot self-emission indicate that $P_4$ shapes may be unquantifiable for DT layered capsules. Instead the positive $P_4$ asymmetry “aliases” itself as an oblate $P_2$ in the x-ray images. Correction of this apparent $P_2$ distortion can further distort the implosion while creating a round x-ray image. Long wavelength asymmetries may be playing a significant role in the observed yield reduction of NIF DT implosions relative to detailed postshot two-dimensional simulations.

Topological insulators and topological superconductors are distinguished by their bulk phase transitions and gapless states at a sharp boundary with the vacuum. Quasicrystals have recently been found to be topologically nontrivial. In quasicrystals, the bulk phase transitions occur in the same manner as standard topological materials, but their boundary phenomena are more subtle. In this Letter we directly observe bulk phase transitions, using photonic quasicrystals, by constructing a smooth boundary between topologically distinct one-dimensional quasicrystals. Moreover, we use the same method to experimentally confirm the topological equivalence between the Harper and Fibonacci quasicrystals.

The relation between bulk topological invariants and experimentally observable physical quantities is a fundamental property of topological insulators and superconductors. In the case of chiral symmetric systems in odd spatial dimensions such as time-reversal invariant topological superconductors and topological insulators with sublattice symmetry, this relation has not been well understood. We clarify that the winding number which characterizes the bulk $Z$ nontriviality of these systems can appear in electromagnetic and thermal responses in a certain class of heterostructure systems. It is also found that the $Z$ nontriviality can be detected in the bulk “chiral polarization,” which is induced by magnetoelectric effects.

We have studied quantized transport in HgTe wells with inverted band structure corresponding to the two-dimensional topological insulator phase (2D TI) with locally controlled density allowing $n\mathrm{\text{−}}p\mathrm{\text{−}}n$ and $n$-2D TI-$n$ junctions. The resistance reveals the fractional plateau $2h/e^2$ in the $n\mathrm{\text{−}}p\mathrm{\text{−}}n$ regime in the presence of the strong perpendicular magnetic field. We found that in the $n$-2D TI-$n$ regime the plateaux in resistance in not universal and results from the edge state equilibration at the interface between chiral and helical edge modes. We provided the simple model describing the resistance quantization in $n$-2D TI-$n$ regime.

By means of the magnetocaloric effect, we examine the nature of the superconducting-normal (S-N) transition of ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$, a most promising candidate for a spin-triplet superconductor. We provide thermodynamic evidence that the S-N transition of this oxide is of first order below approximately 0.8 K and only for magnetic field directions very close to the conducting plane, in clear contrast to the ordinary type-II superconductors exhibiting second-order S-N transitions. The entropy release across the transition at 0.2 K is 10% of the normal-state entropy. Our result urges an introduction of a new mechanism to break superconductivity by magnetic field.