The $\Omega$ phase of the liquid sodium $\alpha \mathrm{\text{−}}\Omega$ dynamo experiment at New Mexico Institute of Mining and Technology in cooperation with Los Alamos National Laboratory has demonstrated a high toroidal field $B_{\varphi }$ that is $\simeq 8\times B_r$, where $B_r$ is the radial component of an applied poloidal magnetic field. This enhanced toroidal field is produced by the rotational shear in stable Couette flow within liquid sodium at a magnetic Reynolds number $\mathrm{Rm}\simeq 120$. Small turbulence in stable Taylor-Couette flow is caused by Ekman flow at the end walls, which causes an estimated turbulence energy fraction of $(\delta v/v{)}^2\sim {10}^{-3}$.

By analyzing high-speed video of the fruit fly, we discover a swimminglike mode of forward flight characterized by paddling wing motions. We develop a new aerodynamic analysis procedure to show that these insects generate drag-based thrust by slicing their wings forward at low angle of attack and pushing backwards at a higher angle. Reduced-order models and simulations reveal that the law for flight speed is determined by these wing motions but is insensitive to material properties of the fluid. Thus, paddling is as effective in air as in water and represents a common strategy for propulsion through aquatic and aerial environments.

We study the adhesion of an elastic sheet on a rigid spherical substrate. Gauss’s Theorema Egregium shows that this operation necessarily generates metric distortions (i.e., stretching) as well as bending. As a result, a large variety of contact patterns ranging from simple disks to complex branched shapes are observed as a function of both geometrical and material properties. We describe these different morphologies as a function of two nondimensional parameters comparing, respectively, bending and stretching energies to adhesion. A complete configuration diagram is finally proposed.

We show that simple laser configurations can give rise to “optical flux lattices,” in which optically dressed atoms experience a periodic effective magnetic flux with high mean density. These potentials lead to narrow energy bands with nonzero Chern numbers. Optical flux lattices will greatly facilitate the achievement of the quantum Hall regime for ultracold atomic gases.

First-principles calculations show that the rich variety of image patterns found in carbon nanostructures with the atomic force and scanning tunneling microscopes can be rationalized in terms of the chemical reactivity of the tip and the distance range explored in the experiments. For weakly reactive tips, the Pauli repulsion dominates the atomic contrast and force maxima are expected on low electronic density positions as the hollow site. With reactive tips, the interaction is strong enough to change locally the hybridization of the carbon atoms, making it possible to observe atomic resolution in both the attractive and the repulsive regime although with inverted contrast. Regarding STM images, we show that in the near-contact regime, due to current saturation, bright spots correspond to hollow positions instead of atomic sites, providing an explanation for the most common hexagonal pattern found in the experiments.

The error rate in complementary transistor circuits is suppressed exponentially in electron number, arising from an intrinsic physical implementation of fault-tolerant error correction. Contrariwise, explicit assembly of gates into the most efficient known fault-tolerant architecture is characterized by a subexponential suppression of error rate with electron number, and incurs significant overhead in wiring and complexity. We conclude that it is more efficient to prevent logical errors with physical fault tolerance than to correct logical errors with fault-tolerant architecture.

We observe an insulator-to-metal transition in crystalline silicon doped with sulfur to nonequilibrium concentrations using ion implantation followed by pulsed-laser melting and rapid resolidification. This insulator-to-metal transition is due to a dopant known to produce only deep levels at equilibrium concentrations. Temperature-dependent conductivity and Hall effect measurements for temperatures $T>1.7\mathrm{K}$ both indicate that a transition from insulating to metallic conduction occurs at a sulfur concentration between 1.8 and $4.3\times {10}^{20}{\mathrm{cm}}^{-3}$. Conduction in insulating samples is consistent with variable-range hopping with a Coulomb gap. The capacity for deep states to effect metallic conduction by delocalization is the only known route to bulk intermediate band photovoltaics in silicon.

We have directly measured quasiparticle number fluctuations in a thin film superconducting Al resonator in thermal equilibrium. The spectrum of these fluctuations provides a measure of both the density and the lifetime of the quasiparticles. We observe that the quasiparticle density decreases exponentially with decreasing temperature, as theoretically predicted, but saturates below 160 mK to $25–55/\mu {\mathrm{m}}^3$. We show that this saturation is consistent with the measured saturation in the quasiparticle lifetime, which also explains similar observations in qubit decoherence times.

A possibility of the amplification of the 7.6 eV $\gamma$ radiation by the stimulated $\gamma$ emission of the ensemble of the ${}^{229m}\mathrm{Th}$ isomeric nuclei in a host dielectric crystal is proved theoretically. This amplification is a result of (1) the excitation of a large number of ${}^{229m}\mathrm{Th}$ isomers by laser radiation, (2) the creation of the inverse population of nuclear levels in a cooled sample owing to the interaction of thorium nuclei with the crystal electric field or with an external magnetic field, (3) the emission or absorption of the optical photons by thorium nuclei in the crystal without recoil, and (4) the nuclear spin relaxation through the conduction electrons of the metallic covering.

We present the first upper limit on gravitational wave (GW) backgrounds at an unexplored frequency of 0.2 Hz using a torsion-bar antenna (TOBA). A TOBA was proposed to search for low-frequency GWs. We have developed a small-scaled TOBA and successfully found ${\Omega }_{\mathrm{gw}}(f)<4.3\times {10}^{17}$ at 0.2 Hz as demonstration of the TOBA’s capabilities, where ${\Omega }_{\mathrm{gw}}(f)$ is the GW energy density per logarithmic frequency interval in units of the closure density. Our result is the first nonintegrated limit to bridge the gap between the LIGO band (around 100 Hz) and the Cassini band (${10}^{-6}–{10}^{-4}\mathrm{Hz}$).

We present evidence for the existence of a bound $H$ dibaryon, an $I=0$, $J=0$, $s=-2$ state with valence quark structure $uuddss$, at a pion mass of $m_{\pi }\sim 389\mathrm{MeV}$. Using the results of lattice QCD calculations performed on four ensembles of anisotropic clover gauge-field configurations, with spatial extents of $L\sim 2.0$, 2.5, 3.0, and 3.9 fm at a spatial lattice spacing of $b_s\sim 0.123\mathrm{fm}$, we find an $H$ dibaryon bound by $B_{\infty }^H=16.6\pm 2.1\pm 4.6\mathrm{MeV}$ at a pion mass of $m_{\pi }\sim 389\mathrm{MeV}$.

The flavor-singlet $H$ dibaryon, which has strangeness $-2$ and baryon number 2, is studied by the approach recently developed for the baryon-baryon interactions in lattice QCD. The flavor-singlet central potential is derived from the spatial and imaginary-time dependence of the Nambu-Bethe-Salpeter wave function measured in $N_f=3$ full QCD simulations with the lattice size of $L\simeq 2,3,4\mathrm{fm}$. The potential is found to be insensitive to the volume, and it leads to a bound $H$ dibaryon with the binding energy of 30–40 MeV for the pseudoscalar meson mass of 673–1015 MeV.

We characterize the response of compressed, sheared polymer-brush bilayers with colloidal inclusions to highly nonstationary inversion processes by means of molecular dynamics simulations and scaling theory. Bilayers with a simple (dimeric) solvent reveal an overshoot for the shear stress, while simulations of dry brushes without explicit solvent molecules fail to display this effect. We demonstrate that mechanical instabilities can be controlled by the inclusion of macromolecular structures, such as colloids of varying softness. Based on a recently developed theory, we suggest a scaling approach to determine a characteristic time for conformational and collective responses.

We place two atoms in quantum superposition states and observe coherent phase evolution for $3.4\times {10}^{15}$ cycles. Correlation signals from the two atoms yield information about their relative phase even after the probe radiation has decohered. This technique allowed a frequency comparison of two ${}^{27}\mathrm{Al}^{+}$ ions with fractional uncertainty ${3.7}_{-0.8}^{+1.0}\times {10}^{-16}/\sqrt{\tau /\mathrm{s}}$. Two measures of the $Q$ factor are reported: The $Q$ factor derived from quantum coherence is ${3.4}_{-1.1}^{+2.4}\times {10}^{16}$, and the spectroscopic $Q$ factor for a Ramsey time of 3 s is $6.7\times {10}^{15}$. We demonstrate a method to detect the individual quantum states of two ${\mathrm{Al}}^{+}$ ions in a ${\mathrm{Mg}}^{+}\mathrm{\text{−}}{\mathrm{Al}}^{+}\mathrm{\text{−}}{\mathrm{Al}}^{+}$ linear ion chain without spatially resolving the ions.

It has recently become possible to focus a beam of high-energy electrons to a spot smaller than an atom, with vast potential for the study of condensed matter. We devise an experiment that can image, with subangstrom resolution, the distribution of such an electron beam as it scatters within an atomic lattice. Our experiments reveal the acute sensitivity of the scattered electron distribution to 0.1 Å shifts of the impact point. Scattering due to plasmon excitations is also examined. Implications for the study of the atomic and electronic structure of condensed matter are discussed.

A mechanism for asymmetric (nonreciprocal) wave transmission is presented. As a reference system, we consider a layered nonlinear, nonmirror-symmetric model described by the one-dimensional discrete nonlinear Schrödinger equation with spatially varying coefficients embedded in an otherwise linear lattice. We construct a class of exact extended solutions such that waves with the same frequency and incident amplitude impinging from left and right directions have very different transmission coefficients. This effect arises already for the simplest case of two nonlinear layers and is associated with the shift of nonlinear resonances. Increasing the number of layers considerably increases the complexity of the family of solutions. Finally, numerical simulations of asymmetric wave packet transmission are presented which beautifully display the rectifying effect.

We have studied a solid-to-plasma transition by irradiating Al foils with the FLASH free electron laser at intensities up to ${10}^{16}\mathrm{W}/{\mathrm{cm}}^2$. Intense XUV self-emission shows spectral features that are consistent with emission from regions of high density, which go beyond single inner-shell photoionization of solids. Characteristic features of intrashell transitions allowed us to identify Auger heating of the electrons in the conduction band occurring immediately after the absorption of the XUV laser energy as the dominant mechanism. A simple model of a multicharge state inverse Auger effect is proposed to explain the target emission when the conduction band at solid density becomes more atomiclike as energy is transferred from the electrons to the ions. This allows one to determine, independent of plasma simulations, the electron temperature and density just after the decay of crystalline order and to characterize the early time evolution.

We show that a chiral ($f+if$)-wave superconducting pairing may be induced in the lowest heavy hole band of a hole-doped semiconductor thin film through proximity contact with an $s$-wave superconductor. The chirality of the pairing originates from the $3\pi$ Berry phase accumulated for a heavy hole moving along a close path on the Fermi surface. There exist three chiral gapless Majorana edge states, in consistence with the chiral ($f+if$)-wave pairing. We show the existence of zero-energy Majorana fermions in vortices in the semiconductor-superconductor heterostructure by solving the Bogoliubov–de Gennes equations numerically as well as analytically in the strong confinement limit.

A giant tunneling electroresistance effect may be achieved in a ferroelectric tunnel junction by exploiting the magnetoelectric effect at the interface between the ferroelectric barrier and a magnetic ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ electrode. Using first-principles density-functional theory we demonstrate that a few magnetic monolayers of ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ near the interface act, in response to ferroelectric polarization reversal, as an atomic-scale spin valve by filtering spin-dependent current. This produces more than an order of magnitude change in conductance, and thus constitutes a giant resistive switching effect.

The change in energy of an ideal Fermi gas when a local one-body potential is inserted into the system, or when the density is changed locally, are important quantities in condensed matter physics. We show that they can be rigorously bounded from below by a universal constant times the value given by the semiclassical approximation.