We present a universal method to create a tunable, artificial vector gauge potential for neutral particles trapped in an optical lattice. The necessary Peierls phase of the hopping parameters between neighboring lattice sites is generated by applying a suitable periodic inertial force such that the method does not rely on any internal structure of the particles. We experimentally demonstrate the realization of such artificial potentials, which generate ground-state superfluids at arbitrary nonzero quasimomentum. We furthermore investigate possible implementations of this scheme to create tunable magnetic fluxes, going towards model systems for strong-field physics.

We propose the measurement of cavity-enhanced parity-nonconserving (PNC) optical rotation in several transitions of metastable Xe and Hg, including Xe ${(}^2{P}_{3/2}^o)6s{}^2[3/2{]}_2^o\to {(}^2{P}_{1/2}^o)6s{}^2[1/2{]}_1^o$ and Hg $6s6p{}^{3}P_2^o\to 6s6p{}^{1}P_1^o$, with calculated amplitude ratios of $E_1^{\mathrm{PNC}}/M1=11\times {10}^{-8}$ and $10\times {10}^{-8}$, respectively. We demonstrate the use of a high-finesse bow-tie cavity with counterpropagating beams and a longitudinal magnetic field, which allows the absolute measurement of chiral optical rotation, with a path length enhancement of about ${10}^4$, necessary for PNC measurement from available column densities of ${10}^{14}{\mathrm{cm}}^{-2}$ for metastable Xe or Hg. Rapid PNC-signal reversal, allowing robust background subtraction, is achieved by shifting the cavity resonance to an opposite polarization mode or by inverting the magnetic field. The precise measurement of isotope and nuclear-spin dependent $E_1^{\mathrm{PNC}}$ amplitudes provides a sensitive low-energy test of the standard model.

We present a study on swelling-induced circumferential buckling of tubular shaped gels. Inhomogeneous stress develops as the gel swells under mechanical constraints, which gives rise to spontaneous buckling instability without an external force. Full control over the postbuckling pattern is experimentally demonstrated. A simple analytical model is developed using elastic energy to predict stability and postbuckling patterns upon swelling. Analysis reveals that the height to diameter ratio is the most critical design parameter to determine the buckling pattern, which agrees well with experimental and numerical results.

We demonstrate, using a combination of experiment and density functional theory, that orbital ordering drives the formation of a one-dimensional (1D) $S=1/2$ antiferromagnetic spin chain in the 3D rocksalt structure of cesium superoxide (${\mathrm{CsO}}_2$). The magnetic superoxide anion (${\mathrm{O}}_2^{-}$) exhibits degeneracy of its $2p$-derived molecular orbitals, which is lifted by a structural distortion on cooling. A spin chain is then formed by zigzag ordering of the half-filled superoxide orbitals, promoting a superexchange pathway mediated by the $p_z$ orbitals of ${\mathrm{Cs}}^{+}$ along only one crystal direction. This scenario is analogous to the $3d$-orbital-driven spin chain found in the perovskite ${\mathrm{KCuF}}_3$ and is the first example of an inorganic quantum spin system with unpaired $p$ electrons.

A measurement of spin correlation in $t\overline{t}$ production is reported using data collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of $2.1{\mathrm{fb}}^{-1}$. Candidate events are selected in the dilepton topology with large missing transverse energy and at least two jets. The difference in azimuthal angle between the two charged leptons in the laboratory frame is used to extract the correlation between the top and antitop quark spins. In the helicity basis the measured degree of correlation corresponds to $A_{\mathrm{helicity}}={0.40}_{-0.08}^{+0.09}$, in agreement with the next-to-leading-order standard model prediction. The hypothesis of zero spin correlation is excluded at 5.1 standard deviations.

Charge correlations in lattice gauge calculations suggest that up, down, and strange charges move independently in the quark-gluon plasma, and that the density of such charges is similar to what is expected from simple thermal arguments. Here, we show how specific elements of the charge-charge correlation matrix in the quark-gluon plasma survive hadronization and become manifest in final-state charge-charge correlation measurements.

Gold deposited on the ${\mathrm{Fe}}_3{\mathrm{O}}_4(001)$ surface at room temperature was studied using scanning tunneling microscopy (STM) and x-ray photoelectron spectroscopy (XPS). This surface forms a $(\sqrt{2}\times \sqrt{2})R45°$ reconstruction, where pairs of Fe and neighboring O ions are slightly displaced laterally producing undulating rows with “narrow” and “wide” hollow sites. At low coverages, single Au adatoms adsorb exclusively at the narrow sites, with no significant sintering up to annealing temperatures of $400°\mathrm{C}$. We propose the strong site preference to be related to charge and orbital ordering within the first subsurface layer of ${\mathrm{Fe}}_3{\mathrm{O}}_4(001)\mathrm{\text{−}}(\sqrt{2}\times \sqrt{2})R45°$. Because of its high thermal stability, this could prove an ideal model system for probing the chemical reactivity of single atomic species.

Among the distinctive features of quasicrystals—structures with long-range order but without periodicity—are phasons. Phasons are hydrodynamic modes that, like phonons, do not cost free energy in the long-wavelength limit. For light-induced colloidal quasicrystals, we analyze the collective rearrangements of the colloids that occur when the phasonic displacement of the light field is changed. The colloidal model system is employed to study the link between the continuous description of phasonic modes in quasicrystals and collective phasonic flips of atoms. We introduce characteristic areas of reduced phononic and phasonic displacements and use them to predict individual colloidal trajectories. In principle, our method can be employed with all quasicrystalline systems in order to derive collective rearrangements of particles from the continuous description of phasons.

We calculate the three-body spectrum for identical bosons interacting via attractive $1/r^2$ potentials. We find an infinite number of three-body states even when the pair interactions are too weak to support any two-body states. These new states thus share this surprising scenario with the Efimov effect, but are not themselves Efimov states. Our effect occurs for both identical bosons and identical fermions, and it persists in the presence of two-body bound states.

We report on the achievement of Bose-Einstein condensation of erbium atoms and on the observation of magnetic Feshbach resonances at low magnetic fields. By means of evaporative cooling in an optical dipole trap, we produce pure condensates of ${}^{168}\mathrm{Er}$, containing up to $7\times {10}^4$ atoms. Feshbach spectroscopy reveals an extraordinary rich loss spectrum with six loss resonances already in a narrow magnetic-field range up to 3 G. Finally, we demonstrate the application of a low-field Feshbach resonance to produce a tunable dipolar Bose-Einstein condensate and we observe its characteristic $d$-wave collapse.

Utilizing a multilayered composite approach, we have designed and constructed a new class of artificial materials for thermal conduction. We show that an engineered material can be utilized to control the diffusive heat flow in ways inconceivable with naturally occurring materials. By shielding, concentrating, and inverting heat current, we experimentally demonstrate the unique potential and the utility of guiding heat flux.

We report the first quantum degenerate dipolar Fermi gas, the realization of which opens a new frontier for exploring strongly correlated physics and, in particular, quantum liquid crystalline phases. A quantum degenerate Fermi gas of the most magnetic atom ${}^{161}\mathrm{Dy}$ is produced by laser cooling to $10\mu \mathrm{K}$ before sympathetically cooling with ultracold, bosonic ${}^{162}\mathrm{Dy}$. The temperature of the spin-polarized ${}^{161}\mathrm{Dy}$ is a factor $T/T_F=0.2$ below the Fermi temperature $T_F=300\mathrm{nK}$. The cotrapped ${}^{162}\mathrm{Dy}$ concomitantly cools to approximately $T_c$ for Bose-Einstein condensation, thus realizing a novel, nearly quantum degenerate dipolar Bose-Fermi gas mixture. Additionally, we achieve the forced evaporative cooling of spin-polarized ${}^{161}\mathrm{Dy}$ without ${}^{162}\mathrm{Dy}$ to $T/T_F=0.7$. That such a low temperature ratio is achieved may be a first signature of universal dipolar scattering.

We report the final results of the Phase II SIMPLE measurements, comprising two run stages of 15 superheated droplet detectors each, with the second stage including an improved neutron shielding. The analyses include a refined signal analysis, and revised nucleation efficiency based on a reanalysis of previously reported monochromatic neutron irradiations. The combined results yield a contour minimum of ${\sigma }_p=5.7\times {10}^{-3}\mathrm{pb}$ at $35\mathrm{GeV}/c^2$ in the spin-dependent sector of weakly interacting massive particle (WIMP) proton interactions, the most restrictive to date for $M_W\le 60\mathrm{GeV}/c^2$ from a direct search experiment and overlapping, for the first time, with results previously obtained only indirectly. In the spin-independent sector, a minimum of $4.7\times {10}^{-6}\mathrm{pb}$ at $35\mathrm{GeV}/c^2$ is achieved, with the exclusion contour challenging a significant part of the light mass WIMP region of current interest.

We theoretically investigate the deflection-induced coupling of an electron spin to vibrational motion due to spin-orbit coupling in suspended carbon nanotube quantum dots. Our estimates indicate that, with current capabilities, a quantum dot with an odd number of electrons can serve as a realization of the Jaynes-Cummings model of quantum electrodynamics in the strong-coupling regime. A quantized flexural mode of the suspended tube plays the role of the optical mode and we identify two distinct two-level subspaces, at small and large magnetic field, which can be used as qubits in this setup. The strong intrinsic spin-mechanical coupling allows for detection, as well as manipulation of the spin qubit, and may yield enhanced performance of nanotubes in sensing applications.

We measure a large valley-orbit splitting for shallow isolated phosphorus donors in a silicon gated nanowire. This splitting is close to the bulk value and well above previous reports in silicon nanostructures. It was determined using a double dopant transport spectroscopy which eliminates artifacts induced by the environment. Quantitative simulations taking into account the position of the donors with respect to the $\mathrm{Si}/{\mathrm{SiO}}_2$ interface and electric field in the wire show that the values found are consistent with the device geometry.

We study the geometrically induced cohesion of ensembles of granular “$u$ particles” that mechanically entangle through particle interpenetration. We vary the length-to-width ratio $l/w$ of the $u$ particles and form them into freestanding vertical columns. In a laboratory experiment, we monitor the response of the columns to sinusoidal vibration (with peak acceleration $\Gamma$). Column collapse occurs in a characteristic time $\tau$ which follows the relation $\tau \propto \exp (\Gamma /\Delta )$. $\Delta$ resembles an activation energy and is maximal at intermediate $l/w$. A simulation reveals that optimal strength results from competition between packing and entanglement.

Using a data sample corresponding to an integrated luminosity of $0.35{\mathrm{fb}}^{-1}$ collected by LHCb in 2011, we report the first evidence of $CP$ violation in the decays of $B_s^0$ mesons to $K^{\pm }{\pi }^{\mp }$ pairs, $A_{CP}(B_s^0\to K\pi )=0.27\pm 0.08(\mathrm{stat})\pm 0.02(\mathrm{syst})$, with a significance of $3.3\sigma$. Furthermore, we report the most precise measurement of $CP$ violation in the decays of $B^0$ mesons to $K^{\pm }{\pi }^{\mp }$ pairs, $A_{CP}(B^0\to K\pi )=-0.088\pm 0.011(\mathrm{stat})\pm 0.008(\mathrm{syst})$, with a significance exceeding $6\sigma$.

We compute the coefficient of the potential three-loop four-point ultraviolet divergence in pure $\mathcal{N}=4$ supergravity and show that it vanishes, contrary to expectations from symmetry arguments. The recently uncovered duality between color and kinematics is used to greatly streamline the calculation. We comment on all-loop cancellations hinting at further surprises awaiting discovery at higher loops.

Departing from the usual paradigm of local operations and classical communication adopted in entanglement theory, we study here the interconversion of quantum states by means of local operations and shared randomness. A set of necessary and sufficient conditions for the existence of such a transformation between two given quantum states is given in terms of the payoff they yield in a suitable class of nonlocal games. It is shown that, as a consequence of our result, such a class of nonlocal games is able to witness quantum entanglement, however weak, and reveal nonlocality in any entangled quantum state. An example illustrating this fact is provided.

The current evaluation of the triple-$\alpha$ reaction rate assumes that the $\alpha$ decay of the 7.65 MeV, $0^{+}$ state in ${}^{12}\mathrm{C}$, commonly known as the Hoyle state, proceeds sequentially via the ground state of ${}^8\mathrm{Be}$. This assumption is challenged by the recent identification of two direct $\alpha$-decay branches with a combined branching ratio of $17(5)\%$. If correct, this would imply a corresponding reduction in the triple-$\alpha$ reaction rate with important astrophysical consequences. We have used the ${}^{11}\mathrm{B}({}^3\mathrm{He},d)$ reaction to populate the Hoyle state and measured the decay to three $\alpha$ particles in complete kinematics. We find no evidence for direct $\alpha$-decay branches, and hence our data do not support a revision of the triple-$\alpha$ reaction rate. We obtain an upper limit of $5\times {10}^{-3}$ on the direct $\alpha$ decay of the Hoyle state at $95\%$ C.L., which is 1 order of magnitude better than a previous upper limit.