We report a novel depth dependence for the penetration of spin current into ultrathin ferromagnets. Ferromagnetic resonance measurements show that transverse spin current pumped into three structurally distinct ferromagnets is attenuated, on reflection, by an amount proportional to the ferromagnetic layer thickness, saturating abruptly at $1.2\pm 0.1\mathrm{nm}$. The observed power-law decay, differing significantly from the (exponential) characteristic-length dependence for longitudinal spin current, confirms models of spin momentum transfer which have been inaccessible to experiment.

Photoelectron spectra of the deprotonated green fluorescent protein chromophore have been measured in the gas phase at several wavelengths within and beyond the $S_0\mathrm{\text{−}}{S}_1$ photoabsorption band of the molecule. The vertical detachment energy (VDE) was determined to be $2.68\pm 0.1\mathrm{eV}$. The data show that the first electronically excited state is bound in the Franck-Condon region, and that electron emission proceeds through an indirect (resonant) electron-emission channel within the corresponding absorption band.

The surface of a thin liquid film with a nonconstant curvature is unstable, as the Laplace pressure drives a flow mediated by viscosity. We present the results of experiments on one of the simplest variable curvature surfaces: a thin polymer film with a step. Height profiles are measured as a function of time for a variety of molecular weights. The evolution of the profiles is shown to be self-similar. This self-similarity offers a precise measurement of the capillary velocity by comparison with numerical solutions of the thin film equation. We also derive a master expression for the time dependence of the excess free energy as a function of the material properties and film geometry. The experiment and theory are in excellent agreement and indicate the effectiveness of stepped polymer films to elucidate nanoscale rheological properties.

Transport processes on spatial networks are representative of a broad class of real world systems which, rather than being independent, are typically interdependent. We propose a measure of utility to capture key features that arise when such systems are coupled together. The coupling is defined in a way that is not solely topological, relying on both the distribution of sources and sinks, and the method of route assignment. Using a toy model, we explore relevant cases by simulation. For certain parameter values, a picture emerges of two regimes. The first occurs when the flows go from many sources to a small number of sinks. In this case, network utility is largest when the coupling is at its maximum and the average shortest path is minimized. The second regime arises when many sources correspond to many sinks. Here, the optimal coupling no longer corresponds to the minimum average shortest path, as the congestion of traffic must also be taken into account. More generally, results indicate that coupled spatial systems can give rise to behavior that relies subtly on the interplay between the coupling and randomness in the source-sink distribution.

The chemical potential of a hard-sphere fluid can be expressed in terms of the contact value of the radial distribution function of a solute particle with a diameter varying from zero to that of the solvent particles. Exploiting the explicit knowledge of such a contact value within the Percus-Yevick theory, and using standard thermodynamic relations, a hitherto unknown Percus-Yevick equation of state, $p/\rho k_{B}T=-(9/\eta )\ln (1-\eta )-(16-31\eta )/2(1-\eta {)}^2$, is unveiled. This equation of state turns out to be better than the one obtained from the conventional virial route. Interpolations between the chemical-potential and compressibility routes are shown to be more accurate than the widely used Carnahan-Starling equation of state. The extension to polydisperse hard-sphere systems is also presented.

Spin selectivity in angle-resolved Auger photoelectron coincidence spectroscopy (AR-APECS) is used to probe electron correlation in ferromagnetic thin films. In particular, exploiting the AR-APECS capability to discriminate Auger electron emission events characterized by valence hole pairs created either in the high or in the low total spin state, a strong correlation effect in the Fe $M_{2,3}VV$ Auger line shape (measured in coincidence with the Fe $3p$ photoelectrons) of $\mathrm{Fe}/\mathrm{Cu}(001)$ thin films is detected and ascribed to interactions within the majority spin subband. Such an assignment follows from a close comparison of the experimental AR-APECS line shapes with the predictions of a model based on spin polarized density functional theory and the Cini-Sawatzky approach.

Recent studies show that two low-energy van Hove singularities (VHSs) seen as two pronounced peaks in the density of states could be induced in a twisted graphene bilayer. Here, we report angle-dependent VHSs of a slightly twisted graphene bilayer studied by scanning tunneling microscopy and spectroscopy. We show that energy difference of the two VHSs follows $\Delta E_{\mathrm{vhs}}\sim \hslash {\nu }_F\Delta K$ between 1.0° and 3.0° [here ${\nu }_F\sim 1.1\times {10}^6\mathrm{m}/\mathrm{s}$ is the Fermi velocity of monolayer graphene, and $\Delta K=2K\sin (\theta /2)$ is the shift between the corresponding Dirac points of the twisted graphene bilayer]. This result indicates that the rotation angle between graphene sheets does not result in a significant reduction of the Fermi velocity, which quite differs from that predicted by band structure calculations. However, around a twisted angle $\theta \sim 1.3°$, the observed $\Delta E_{\mathrm{vhs}}\sim 0.11\mathrm{eV}$ is much smaller than the expected value $\hslash {\nu }_F\Delta K\sim 0.28\mathrm{eV}$ at 1.3°. The origin of the reduction of $\Delta E_{\mathrm{vhs}}$ at 1.3° is discussed.

We study the composite charged spin texture (CST) over the Moore-Read quantum Hall state that arises when a collection of elementary CSTs is moved to the same location. Following an algebraic approach based on the characteristic pair correlations of the Moore-Read state, we find that the spin texture associated with a composite CST is set by the fusion sector of the underlying non-Abelian quasiparticles. This phenomenon provides a novel way to read out the quantum register of a non-Abelian topologically ordered phase.

Spin fluctuations are reported near the magnetic field—driven quantum critical point in ${\mathrm{YbRh}}_2{\mathrm{Si}}_2$. On cooling, ferromagnetic fluctuations evolve into incommensurate correlations located at ${\mathbf{q}}_{\mathbf{0}}=\pm \left(\delta ,\delta \right)$, with $\delta =0.14\pm 0.04\mathrm{r}.\mathrm{l}.\mathrm{u}.$ At low temperatures, an in-plane magnetic field induces a sharp intradoublet resonant excitation at an energy $E_0=g{\mu }_B{\mu }_{0}H$ with $g=3.8\pm 0.2$. The intensity is localized at the zone center, indicating precession of spin density extending $\xi =6\pm 2\AA$ beyond the $4f$ site.

A precision-machined cross-slot flow geometry with a shape that has been optimized by numerical simulation of the fluid kinematics is fabricated and used to measure the extensional viscosity of a dilute polymer solution. Full-field birefringence microscopy is used to monitor the evolution and growth of macromolecular anisotropy along the stagnation point streamline, and we observe the formation of a strong and uniform birefringent strand when the dimensionless flow strength exceeds a critical Weissenberg number ${\mathrm{Wi}}_{\mathrm{crit}}\approx 0.5$. Birefringence and bulk pressure drop measurements provide self-consistent estimates of the planar extensional viscosity of the fluid over a wide range of deformation rates ($26{\mathrm{s}}^{-1}\le \dot{\epsilon }\le 435{\mathrm{s}}^{-1}$) and are also in close agreement with numerical simulations performed by using a finitely extensible nonlinear elastic dumbbell model.

Crystalline and amorphous materials composed of the same atoms exhibit strikingly different properties. Likewise, the behavior of materials composed of mesoscale particles depends on the arrangement of their constituent particles. Here, we demonstrate control over particle arrangement during agglomeration. We obtain disordered and ordered agglomerates of the same alkyl thiol-coated gold nanoparticles depending on temperature and solvent. We find that ordered agglomeration occurs exclusively above the melting temperature of the ligand shells. Many-particle simulations show that the contact mechanics of the ligand shells dominate the order-disorder transition: Purely spherical particle-particle interactions yield order, whereas localized “stiction” between the ligand shells leads to disorder. This indicates that the “stickiness” and the packing of the agglomerates can be switched by the state of the ligand shells. It suggests that contact mechanics govern ordering in a wide range of nanoparticles.

The world is addicted to ranking: everything, from the reputation of scientists, journals, and universities to purchasing decisions is driven by measured or perceived differences between them. Here, we analyze empirical data capturing real time ranking in a number of systems, helping to identify the universal characteristics of ranking dynamics. We develop a continuum theory that not only predicts the stability of the ranking process, but shows that a noise-induced phase transition is at the heart of the observed differences in ranking regimes. The key parameters of the continuum theory can be explicitly measured from data, allowing us to predict and experimentally document the existence of three phases that govern ranking stability.

Migratory birds and other species have the ability to navigate by sensing the geomagnetic field. Recent experiments indicate that the essential process in the navigation takes place in the bird’s eye and uses chemical reaction involving molecular ions with unpaired electron spins (radical pair). Sensing is achieved via geomagnetic-dependent dynamics of the spins of the unpaired electrons. Here we utilize the results of two behavioral experiments conducted on European robins to argue that the average lifetime of the radical pair is of the order of a microsecond and therefore agrees with experimental estimations of this parameter for cryptochrome—a pigment believed to form the radical pairs. We also find a reasonable parameter regime where the sensitivity of the avian compass is enhanced by environmental noise, showing that long coherence time is not required for navigation and may even spoil it.

Linear field perturbations of a black hole are described by the Green function of the wave equation that they obey. After Fourier decomposing the Green function, its two natural contributions are given by poles (quasinormal modes) and a largely unexplored branch cut in the complex frequency plane. We present new analytic methods for calculating the branch cut on a Schwarzschild black hole for arbitrary values of the frequency. The branch cut yields a power-law tail decay for late times in the response of a black hole to an initial perturbation. We determine explicitly the first three orders in the power-law and show that the branch cut also yields a new logarithmic behavior $T^{-2\ell -5}\ln T$ for late times. Before the tail sets in, the quasinormal modes dominate the black hole response. For electromagnetic perturbations, the quasinormal mode frequencies approach the branch cut at large overtone index $n$. We determine these frequencies up to $n^{-5/2}$ and, formally, to arbitrary order. Highly damped quasinormal modes are of particular interest in that they have been linked to quantum properties of black holes.

We present a novel experimental tool allowing for kinematically complete studies of break-up processes of laser-cooled atoms. This apparatus, the ’MOTReMi,’ is a combination of a magneto-optical trap (MOT) and a reaction microscope (ReMi). Operated in an ion-storage ring, the new setup enables us to study the dynamics in swift ion-atom collisions on an unprecedented level of precision and detail. In the inaugural experiment on collisions with $1.5\mathrm{MeV}/\mathrm{amu}$ ${\mathrm{O}}^{8+}$-Li the pure ionization of the valence electron as well as the ionization-excitation of the lithium target was investigated.

We demonstrate, for the first time, that photonic lattices support a new type of laser filaments, called lattice filaments (LF). The LF attributes (length, width, and intensity) can be tailored by both varying the photonic lattice properties and also dynamically through the interaction between filaments. This opens the way for extensive all-optical control of the nonlinear propagation of intense ultrafast wave packets. Our approach is generic and applicable to all transparent media, with potential strong impact on various photonic applications.

Bistable structures associated with nonlinear deformation behavior, exemplified by the Venus flytrap and slap bracelet, can switch between different functional shapes upon actuation. Despite numerous efforts in modeling such large deformation behavior of shells, the roles of mechanical and nonlinear geometric effects on bistability remain elusive. We demonstrate, through both theoretical analysis and tabletop experiments, that two dimensionless parameters control bistability. Our work classifies the conditions for bistability, and extends the large deformation theory of plates and shells.

We report results for the temperature profiles of turbulent Rayleigh-Bénard convection (RBC) in the interior of a cylindrical sample of aspect ratio $\Gamma \equiv D/L=0.50$ ($D$ and $L$ are the diameter and height, respectively). Both in the classical and in the ultimate state of RBC we find that the temperature varies as $A\times \ln (z/L)+B$, where $z$ is the distance from the bottom or top plate. In the classical state, the coefficient $A$ decreases in the radial direction as the distance from the side wall increases. For the ultimate state, the radial dependence of $A$ has not yet been determined. These findings are based on experimental measurements over the Rayleigh-number range $4\times {10}^{12}\lesssim \mathrm{Ra}\lesssim {10}^{15}$ for a Prandtl number $\mathrm{Pr}\simeq 0.8$ and on direct numerical simulation at $\mathrm{Ra}=2\times {10}^{12}$, $2\times {10}^{11}$, and $2\times {10}^{10}$, all for $\mathrm{Pr}=0.7$.

We report new experimental results which suggest that the generation of extreme wave events in the Faraday surface ripples is related to the increase in the horizontal mobility of oscillating solitons (oscillons). The analysis of the oscillon trajectories in a horizontal plane shows that at higher vertical acceleration, oscillons move chaotically, merge and form enclosed areas on the water surface. The probability of the formation of such craters, which precede large wave events, increases with the increase in horizontal mobility.

We obtain an exact expression for the time evolution of the interacting Bose gas following a quench from a generic initial state using the Yudson representation for integrable systems. We study the time evolution of the density and noise correlation for a small number of bosons and their asymptotic behavior for any number. We show that for any value of the coupling, as long as it is repulsive, the system asymptotes towards a strongly repulsive gas, while for any value of an attractive coupling the long time behavior is dominated by the maximal bound state. This occurs independently of the initial state and can be viewed as an emerging “dynamic universality.”