The first measurement of the momentum distribution for one-neutron removal from ${}^{24}\mathrm{O}$ at $920A\mathrm{MeV}$ performed at GSI, Darmstadt is reported. The observed distribution has a width (FWHM) of $99\pm 4\mathrm{MeV}/c$ in the projectile rest frame and a one-neutron removal cross section of $63\pm 7\mathrm{mb}$. The results are well explained with a nearly pure $2s_{1/2}$ neutron spectroscopic factor of $1.74\pm 0.19$ within the eikonal model. This large $s$-wave probability shows a spherical shell closure thereby confirming earlier suggestions that ${}^{24}\mathrm{O}$ is a new doubly magic nucleus.

The $A/Z$ dependence of projectile fragmentation at relativistic energies has been studied with the ALADIN forward spectrometer at SIS. A stable beam of ${}^{124}\mathrm{Sn}$ and radioactive beams of ${}^{124}\mathrm{La}$ and ${}^{107}\mathrm{Sn}$ at 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the $A/Z$ of the produced spectator sources, consistent with predictions for expanded systems. Small Coulomb effects ($\Delta T\approx 0.6\mathrm{MeV}$) appear for residue production near the onset of multifragmentation.

We report the Bragg spectroscopy of interacting one-dimensional Bose gases loaded in an optical lattice across the superfluid to the Mott-insulator phase transition. Elementary excitations are created with a nonzero momentum and the response of the correlated 1D gases is in the linear regime. The complexity of the strongly correlated quantum phases is directly displayed in the spectra which exhibit novel features. This work paves the way for a precise characterization of the state of correlated gases in optical lattices.

Observation of coherent single-electron dynamics is severely limited by experimental bandwidth. We present a method to overcome this using moving quantum dots defined by surface acoustic waves. Each dot holds a single electron, and travels through a static potential landscape. When the dot passes abruptly between regions of different confinement, the electron is excited into a superposition of states, and oscillates unitarily from side to side. We detect these oscillations by using a weak, repeated measurement of the current across a tunnel barrier, and find close agreement with simulations.

Magnetic order in graphene-related structures can arise from size effects or from topological frustration. We introduce a rigorous classification scheme for the types of finite graphene structures (nanoflakes) which lead to large net spin or to antiferromagnetic coupling between groups of electron spins. Based on this scheme, we propose specific examples of structures that can serve as the fundamental (NOR and NAND) logic gates for the design of high-density ultrafast spintronic devices. We demonstrate, using ab initio electronic structure calculations, that these gates can in principle operate at room temperature with very low and correctable error rates.

We report on the extraordinary superionic conductivity in the fulleride polymer ${\mathrm{Li}}_4{\mathrm{C}}_{60}$, a crystalline material with no disorder. ${}^7\mathrm{Li}$, NMR, and dc frequency dependent conductivity show uncorrelated ionic hopping across small energy barriers ($\Delta E_a\sim 200\mathrm{meV}$) and an ionic conductivity of ${10}^{-2}\mathrm{S}/\mathrm{cm}$ at room temperature, higher than in “standard” ionic conductors. Ab initio calculations of the molecular structure find intrinsic unoccupied interstitial sites that can be filled by ${\mathrm{Li}}^{+}$ cations in stoichiometric ${\mathrm{Li}}_4{\mathrm{C}}_{60}$ even at low temperatures. The low energy required for the occupation of these sites allows a sizable ${\mathrm{Li}}^{+}$ diffusion above 130 K. The results suggest novel application of lithium intercalated fullerides as electrodes in Li ions batteries.

A nonperturbative theory is presented which allows us to calculate the solvation free energy of polarizable ions near water-vapor and water-oil interfaces. The theory predicts that larger halogen anions are adsorbed at the interface, while the alkali metal cations are repelled from it. The density profiles calculated theoretically are similar to those obtained using molecular dynamics simulations with polarizable force fields.

We simulate the evolution of the steady-state interface in the selective withdrawal regime. Selective withdrawal ends when the upward pull exerted by the viscous flow in the withdrawing liquid layer overcomes the downward force due to surface tension. The lower-layer dynamics are unimportant. The dominant contribution to the surface-tension force comes from the large area where the interface is weakly deflected, instead of the small area where the surface is most distorted. A scaling estimate based on this idea yields results that agree quantitatively with both simulations and previous experiments.

We report on the measurement of four-body recombination rate coefficients in an atomic gas. Our results obtained with an ultracold sample of cesium atoms at negative scattering lengths show a resonant enhancement of losses and provide strong evidence for the existence of a pair of four-body states, which is strictly connected to Efimov trimers via universal relations. Our findings confirm recent theoretical predictions and demonstrate the enrichment of the Efimov scenario when a fourth particle is added to the generic three-body problem.

The results of measurements of the production of neutron-rich nuclei by the fragmentation of a ${}^{76}\mathrm{Ge}$ beam are presented. The cross sections were measured for a large range of nuclei including 15 new isotopes that are the most neutron-rich nuclides of the elements chlorine to manganese (${}^{50}\mathrm{Cl}$, ${}^{53}\mathrm{Ar}$, ${}^{55,56}\mathrm{K}$, ${}^{57,58}\mathrm{Ca}$, ${}^{59,60,61}\mathrm{Sc}$, ${}^{62,63}\mathrm{Ti}$, ${}^{65,66}\mathrm{V}$, ${}^{68}\mathrm{Cr}$, ${}^{70}\mathrm{Mn}$). The enhanced cross sections of several new nuclei relative to a simple thermal evaporation framework, previously shown to describe similar production cross sections, indicates that nuclei in the region around ${}^{62}\mathrm{Ti}$ might be more stable than predicted by current mass models and could be an indication of a new island of inversion similar to that centered on ${}^{31}\mathrm{Na}$.

We numerically study the topology of optical vortex lines (nodal lines) in volumes of optical speckle, modeled as superpositions of random plane waves. It is known that the vortex lines may be infinitely long, or form closed loops. Loops are occasionally threaded by infinite lines, or linked with other loops. We find the probability of a loop not being threaded decays exponentially with the length of the loop. This behavior has a similarity to scaling laws studied in superfluid turbulence, and polymers modeled as random walks.

Measurements are presented of a device designed to cool a $6\mu {\mathrm{m}}^2$ region of 2D electron gas using quantum dots. Electrostatic effects are found to be significant in the device, and a model that accounts for them is developed. At ambient electron temperatures above 120 mK the results are consistent with the model and the base temperature of the cooled region is estimated. At an ambient electron temperature of 280 mK, the $6\mu {\mathrm{m}}^2$ region is found to be cooled below 190 mK. Below 120 mK the results deviate from predictions, which is attributed to reduced electron-electron scattering rates.

We investigate the efficiency of power generation by thermochemical engines. For strong coupling between the particle and heat flows and in the presence of a left-right symmetry in the system, we demonstrate that the efficiency at maximum power displays universality up to quadratic order in the deviation from equilibrium. A maser model is presented to illustrate our argument.

The cross sections for the formation of positronium in the $2P$ state in collisions of positrons with He, Ar, and Xe atoms have been determined by measuring coincidences between the remnant ion and the Lyman-$\alpha$ photon from positronium. The maximum fractional contributions of these to the total Ps formation cross sections increase from approximately $0.06\pm 0.01$ in He to $0.12\pm 0.04$ in Ar and $0.26\pm 0.09$ in Xe. In the case of He, good agreement is found with a coupled-state calculation; for Ar and Xe, measurements are compared with a distorted-wave Born approximation.

Disorder plays an important role in two dimensions, and is responsible for striking phenomena such as metal-insulator transition and the integral and fractional quantum Hall effects. In this Letter, we investigate the role of disorder in the context of the recently discovered topological insulator, which possesses a pair of helical edge states with opposing spins moving in opposite directions and exhibits the phenomenon of quantum spin Hall effect. We predict an unexpected and nontrivial quantum phase termed “topological Anderson insulator,” which is obtained by introducing impurities in a two-dimensional metal; here disorder not only causes metal-insulator transition, as anticipated, but is fundamentally responsible for creating extended edge states. We determine the phase diagram of the topological Anderson insulator and outline its experimental consequences.

A high velocity impact between a liquid droplet and a solid surface produces a splash. Classical work traced the origin of the splash to a thin sheet of fluid ejected near the impact point. Mechanisms of sheet formation have heretofore relied on initial contact of the droplet and the surface. We demonstrate that, neglecting intermolecular forces between the liquid and the solid, the liquid does not contact the solid, and instead spreads on a very thin air film. The interface of the droplet develops a high curvature and emits capillary waves.

The damping of magnetization, represented by the rate at which it relaxes to equilibrium, is successfully modeled as a phenomenological extension in the Landau-Lifschitz-Gilbert equation. This is the damping torque term known as Gilbert damping and its direction is given by the vector product of the magnetization and its time derivative. Here we derive the Gilbert term from first-principles by a nonrelativistic expansion of the Dirac equation. We find that this term arises when one calculates the time evolution of the spin observable in the presence of the full spin-orbital coupling terms, while recognizing the relationship between the curl of the electric field and the time-varying magnetic induction.

We use a two-photon dressing field to create an effective vector gauge potential for Bose-Einstein-condensed atoms in the hyperfine ground state. These Raman-dressed states are spin and momentum superpositions, and we adiabatically load the atoms into the lowest energy dressed state. The effective Hamiltonian of these neutral atoms is like that of charged particles in a uniform magnetic vector potential whose magnitude is set by the strength and detuning of the Raman coupling. The spin and momentum decomposition of the dressed states reveals the strength of the effective vector potential, and our measurements agree quantitatively with a simple single-particle model. While the uniform effective vector potential described here corresponds to zero magnetic field, our technique can be extended to nonuniform vector potentials, giving nonzero effective magnetic fields.

The authors have measured the magnetic response of 33 individual cold mesoscopic gold rings, one ring at a time. The response of some sufficiently small rings has a component that is periodic in the flux through the ring and is attributed to a persistent current. Its period is close to $h/e$, and its sign and amplitude vary between rings. The amplitude distribution agrees well with predictions for the typical $h/e$ current in diffusive rings. The temperature dependence of the amplitude, measured for four rings, is also consistent with theory. These results disagree with previous measurements of three individual metal rings that showed a much larger periodic response than expected. The use of a scanning SQUID microscope enabled in situ measurements of the sensor background. A paramagnetic linear susceptibility and a poorly understood anomaly around a zero field are attributed to defect spins.

Time-resolved Schottky mass spectrometry has been applied to uranium projectile fragments which yielded the mass value for the ${}^{208}\mathrm{Hg}$ ($Z=80$, $N=128$) isotope. The mass excess value of $\mathrm{ME}=-13265(31)\mathrm{keV}$ has been obtained, which has been used to determine the proton-neutron interaction strength in ${}^{210}\mathrm{Pb}$, as a double difference of atomic masses. The results show a dramatic variation of the strength for lead isotopes when crossing the $N=126$ neutron shell closure, thus confirming the empirical predictions that this interaction strength is sensitive to the overlap of the wave functions of the last valence neutrons and protons.