We report the first demonstration of anisotropic step-flow growth of organic molecules on a semiconducting substrate using metal phthalocyanine thermally deposited on the deactivated Si(111)-B $\sqrt{3}\times \sqrt{3}$ $R30°$ surface. With scanning probe microscopy and geometric modeling, we prove the quasiepitaxial nature of this step-flow growth that exhibits no true commensurism, despite a single dominant long-range ordered relationship between the organic crystalline film and the substrate, uniquely distinct from inorganic epitaxial growth. This growth mode can likely be generalized for a range of organic molecules on deactivated Si surfaces and access to it offers new potential for the integration of ordered organic thin films in silicon-based electronics.

By calculation of a thermodynamic phase diagram we provide an atomistic understanding of the morphological changes in ZnO-supported Cu nanocatalysts, which are subject to strong metal-support interactions, in response to the redox properties of the surrounding gas phase, i.e., depending on temperature and pressure. The reactivity, and thus the strong metal-support interactions, of this catalyst is traced back to a redox-state dependent occupation of delocalized ZnO substrate bands and localized Cu cluster states at the Fermi level. It is shown that at the conditions of industrial methanol synthesis complex electronic charge transfer processes across the metal-support interface, driven by morphological and electronic changes, explain the enhanced catalytic reactivity toward ${\mathrm{CO}}_2$.

We introduce a versatile method to compute electronic steady-state properties of strongly correlated extended quantum systems out of equilibrium. The approach is based on dynamical mean-field theory (DMFT), in which the original system is mapped onto an auxiliary nonequilibrium impurity problem imbedded in a Markovian environment. The steady-state Green’s function of the auxiliary system is solved by full diagonalization of the corresponding Lindblad equation. The approach can be regarded as the nontrivial extension of the exact-diagonalization-based DMFT to the nonequilibrium case. As a first application, we consider an interacting Hubbard layer attached to two metallic leads and present results for the steady-state current and the nonequilibrium density of states.

Early experiments on spin-blockaded double quantum dots revealed robust, large-amplitude current oscillations in the presence of a static (dc) source-drain bias. Despite experimental evidence implicating dynamical nuclear polarization, the mechanism has remained a mystery. Here we introduce a minimal albeit realistic model of coupled electron and nuclear spin dynamics which supports self-sustained oscillations. Our mechanism relies on a nuclear spin analog of the tunneling magnetoresistance phenomenon (spin-dependent tunneling rates in the presence of an inhomogeneous Overhauser field) and nuclear spin diffusion, which governs dynamics of the spatial profile of nuclear polarization. The proposed framework naturally explains the differences in phenomenology between vertical and lateral quantum dot structures as well as the extremely long oscillation periods.

The Anderson impurity problem is considered for a graphene bilayer subject to a gap-opening bias. In-gap localized states are produced even when the impurity level overlaps with the continuum of band electrons. The effect depends strongly on the polarity of the applied bias as long as hybridization with the impurity occurs within a single layer. For an impurity level inside the conduction band a positive bias creates the new localized in-gap state. A negative bias does not produce the same result and leads to a simple broadening of the impurity level. The implications for transport are discussed including a possibility of the gate-controlled Kondo effect.

The controlled switching between two quasistable Néel states in adsorbed antiferromagnetic Fe chains has recently been achieved by Loth et al. [Science 335, 196 (2012)] using tunneling electrons from an STM tip. In order to rationalize their data, we evaluate the rate of tunneling electron-induced switching between the Néel states. Good agreement is found with the experiment, permitting us to identify three switching mechanisms: (i) low STM voltage direct electron-induced transitions, (ii) intermediate STM voltage switching via spin-wave-like excitation, and (iii) high STM voltage transitions mediated by domain-wall formation. Spin correlations in the antiferromagnetic chains are the switching driving force, leading to a marked chain-size dependence.

We propose a model for the multiorbital material ${\mathrm{Sr}}_2{\mathrm{CrOsO}}_6$, an insulator with remarkable magnetic properties and the highest $T_c\simeq 725\mathrm{K}$ among all perovskites with a net moment. We derive a new criterion for the Mott transition $({\tilde{U}}_1{\tilde{U}}_2{)}^{1/2}>2.5W$ by using slave-rotor mean field theory, where $W$ is the bandwidth and ${\tilde{U}}_{1(2)}$ are the effective Coulomb interactions on Cr(Os) including Hund’s coupling. We show that ${\mathrm{Sr}}_2{\mathrm{CrOsO}}_6$ is a Mott insulator, where the large Cr ${\tilde{U}}_1$ compensates for the small Os ${\tilde{U}}_2$. The spin sector is described by a frustrated antiferromagnetic Heisenberg model that naturally explains the net moment arising from canting and also the observed nonmonotonic magnetization $M(T)$. We predict characteristic magnetic structure factor peaks that can be probed by neutron experiments.

We study the effect of disorder on frustrated dimerized spin-$1/2$ chains at the Majumdar-Ghosh point. Using variational methods and density-matrix renormalization group approaches, we identify two localization mechanisms for spinons which are the deconfined fractional elementary excitations of these chains. The first one belongs to the Anderson localization class and dominates at the random Majumdar-Ghosh point. There, spinons remain gapped and localize in Lifshitz states whose localization length is analytically obtained. The other mechanism is a random confinement mechanism which induces an effective interaction between spinons and brings the chain into a gapless and partially polarized phase for arbitrarily small disorder.

We study the magnetic relaxation rate $\Gamma$ of the single-molecule magnet ${\mathrm{Mn}}_{12}\mathrm{\text{−}}t\mathrm{BuAc}$ as a function of the magnetic field component $H_T$ transverse to the molecule’s easy axis. When the spin is near a magnetic quantum tunneling resonance, we find that $\Gamma$ increases abruptly at certain values of $H_T$. These increases are observed just beyond values of $H_T$ at which a geometric-phase interference effect suppresses tunneling between two excited energy levels. The effect is washed out by rotating $H_T$ away from the spin’s hard axis, thereby suppressing the interference effect. Detailed numerical calculations of $\Gamma$ using the known spin Hamiltonian accurately reproduce the observed behavior. These results are the first experimental evidence for geometric-phase interference in a single-molecule magnet with true fourfold symmetry.

$\mathrm{CoO}/\mathrm{Al}$-doped ZnO (AZO) multilayers exhibit ferromagnetism up to $\sim 300\mathrm{K}$. The magnetic behavior oscillates with odd vs even number of Co layers in the insulating antiferromagnetic CoO and (separately) with the thickness of the AZO layers and vanishes if AZO is replaced by intrinsic ZnO. Magnetization is due to uncompensated (111) ferromagnetic planes of insulating CoO for odd numbers of atomic planes per layer that are coupled together via RKKY exchange mediated by electron carriers in the nonmagnetic AZO layers. The period of the oscillation with AZO thickness qualitatively matches the Fermi wave vector calculated from the carrier concentration measured by ordinary Hall effect. Magnetic polarization of the AZO carriers is confirmed via an anomalous Hall effect that is proportional to the magnetization.

We report a high-resolution resonant inelastic soft x-ray scattering study of the quantum magnetic spin-chain materials ${\mathrm{Li}}_2{\mathrm{CuO}}_2$ and ${\mathrm{CuGeO}}_3$. By tuning the incoming photon energy to the oxygen $K$ edge, a strong excitation around 3.5 eV energy loss is clearly resolved for both materials. Comparing the experimental data to many-body calculations, we identify this excitation as a Zhang-Rice singlet exciton on neighboring ${\mathrm{CuO}}_4$ plaquettes. We demonstrate that the strong temperature dependence of the inelastic scattering related to this high-energy exciton enables us to probe short-range spin correlations on the 1 meV scale with outstanding sensitivity.

Bilayer membranes self-assembled from simple amphiphiles in solution always have a planar ground-state shape. This is a consequence of several internal relaxation mechanisms of the membrane and prevents the straightforward control of vesicle size. Here, we show that this principle can be circumvented and that direct size control by molecular design is a realistic possibility. Using coarse-grained calculations, we design tetrablock copolymers that form membranes with a preferred curvature and demonstrate how to form low-polydispersity vesicles while suppressing micellization.

In the absence of advection, reaction-diffusion systems are able to organize into spatiotemporal patterns, in particular spiral and target waves. Whenever advection is present that can be parametrized in terms of effective or turbulent diffusion $D_{*}$, these patterns should be attainable on a much greater, boosted length scale. However, so far, experimental evidence of these boosted patterns in a turbulent flow was lacking. Here, we report the first experimental observation of boosted target and spiral patterns in an excitable chemical reaction in a quasi-two-dimensional turbulent flow. The wave patterns observed are $\sim 50$ times larger than in the case of molecular diffusion only. We vary the turbulent diffusion coefficient $D_{*}$ of the flow and find that the fundamental Fisher-Kolmogorov-Petrovsky-Piskunov equation, $v_f\propto \sqrt{D_{*}}$, for the asymptotic speed of a reactive wave remains valid. However, not all measures of the boosted wave scale with $D_{*}$ as expected from molecular diffusion, since the wave fronts turn out to be highly filamentous.

We compute cosmic ray (CR) nuclei, proton, antiproton, electron, and positron spectra below 1 TeV at Earth by means of a detailed transport description in the galaxy and in the solar system. CR spectra below 10 GeV are strongly modified by charge-sign dependent propagation effects. These depend on the polarity of the solar magnetic field and therefore vary with the solar cycle. The puzzling discrepancy between the low-energy positron fraction measured by PAMELA and AMS-01 is then easily explained by their different data-taking epochs. We reproduce the observed spectra of CR light nuclei within the same galactic and solar-system propagation model.

Super-Eddington accreting massive black holes (SEAMBHs) reach saturated luminosities above a certain accretion rate due to photon trapping and advection in slim accretion disks. We show that these SEAMBHs could provide a new tool for estimating cosmological distances if they are properly identified by hard x-ray observations, in particular by the slope of their 2–10 keV continuum. To verify this idea we obtained black hole mass estimates and x-ray data for a sample of 60 narrow line Seyfert 1 galaxies that we consider to be the most promising SEAMBH candidates. We demonstrate that the distances derived by the new method for the objects in the sample get closer to the standard luminosity distances as the hard x-ray continuum gets steeper. The results allow us to analyze the requirements for using the method in future samples of active black holes and to demonstrate that the expected uncertainty, given large enough samples, can make them into a useful, new cosmological ruler.

We argue that generic nonrelativistic quantum field theories with a holographic description are dual to Hořava gravity. We construct explicit examples of this duality embedded in string theory by starting with relativistic dual pairs and taking a nonrelativistic scaling limit.

We argue that Hořava-Lifshitz (HL) gravity provides the minimal holographic dual for Lifshitz-type field theories with anisotropic scaling and a dynamical exponent $z$. First we show that Lifshitz spacetimes are vacuum solutions of HL gravity, without need for additional matter. Then we perform holographic renormalization of HL gravity, and show how it reproduces the full structure of the $z=2$ anisotropic Weyl anomaly in dual field theories in $2+1$ dimensions, while its minimal relativistic gravity counterpart yields only one of two independent central charges in the anomaly.

A novel approach based on the projection of the Penning-trap ion motion onto a position-sensitive detector opens the door to very accurate mass measurements on the ppb level even for short-lived nuclides with half-lives well below a second. In addition to the accuracy boost, the new method provides a superior resolving power by which low-lying isomeric states with excitation energy on the 10-keV level can be easily separated from the ground state. A measurement of the mass difference of ${}^{130}\mathrm{Xe}$ and ${}^{129}\mathrm{Xe}$ has demonstrated the great potential of the new approach.

A long-lived $J^{\pi }=4_1^{+}$ isomer, $T_{1/2}=2.2(1)\mathrm{ms}$, has been discovered at 643.4(1) keV in the weakly bound ${}_9{}^{26}\mathrm{F}$ nucleus. It was populated at Grand Accélérateur National d’Ions Lourds in the fragmentation of a ${}^{36}\mathrm{S}$ beam. It decays by an internal transition to the $J^{\pi }=1_1^{+}$ ground state [82(14)%], by $\beta$ decay to ${}^{26}\mathrm{Ne}$, or $\beta$-delayed neutron emission to ${}^{25}\mathrm{Ne}$. From the $\beta$-decay studies of the $J^{\pi }=1_1^{+}$ and $J^{\pi }=4_1^{+}$ states, new excited states have been discovered in ${}^{25,26}\mathrm{Ne}$. Gathering the measured binding energies of the $J^{\pi }=1_1^{+}-4_1^{+}$ multiplet in ${}_9{}^{26}\mathrm{F}$, we find that the proton-neutron $\pi 0d_{5/2}\nu 0d_{3/2}$ effective force used in shell-model calculations should be reduced to properly account for the weak binding of ${}_9{}^{26}\mathrm{F}$. Microscopic coupled cluster theory calculations using interactions derived from chiral effective field theory are in very good agreement with the energy of the low-lying $1_1^{+}$, $2_1^{+}$, $4_1^{+}$ states in ${}^{26}\mathrm{F}$. Including three-body forces and coupling to the continuum effects improve the agreement between experiment and theory as compared to the use of two-body forces only.

In this Letter we present experimental results concerning the retrieval of images of absorbing objects immersed in turbid media via differential ghost imaging (DGI) in a backscattering configuration. The method has been applied, for the first time to our knowledge, to the imaging of thin black objects located inside a turbid solution in proximity of its surface. We show that it recovers images with a contrast better than standard noncorrelated direct imaging, but equivalent to noncorrelated diffusive imaging. A simple theoretical model capable of describing the basic optics of DGI in turbid media is proposed.