The Canadian Penning Trap mass spectrometer has made mass measurements of 33 neutron-rich nuclides provided by the new Californium Rare Isotope Breeder Upgrade facility at Argonne National Laboratory. The studied region includes the ${}^{132}\mathrm{Sn}$ double shell closure and ranges in $Z$ from In to Cs, with Sn isotopes measured out to $A=135$, and the typical measurement precision is at the 100 ppb level or better. The region encompasses a possible major waiting point of the astrophysical $r$ process, and the impact of the masses on the $r$ process is shown through a series of simulations. These first-ever simulations with direct mass information on this waiting point show significant increases in waiting time at Sn and Sb in comparison with commonly used mass models, demonstrating the inadequacy of existing models for accurate $r$-process calculations.

Crystallization in a two-dimensional strongly coupled plasma from a rapidly cooled fluid is found to be efficiently blocked by an external magnetic field. Beyond a threshold of the magnetic field strength $B$, the relaxation time to the equilibrium crystal increases exponentially with $B$, which is attributed to an impeded conversion of potential to kinetic energy. Our finding is opposed to the standard picture of two-dimensional freezing of one-component systems which does not exhibit a nucleation barrier and opens the way to keep two-dimensional fluids metastable over long times.

The inverse spin Hall effect (ISHE) has been observed only in nonmagnetic metals, such as Pt and Au, with a strong spin-orbit coupling. We report the observation of ISHE in a ferromagnetic permalloy (Py) on ferromagnetic insulator yttrium iron garnet (YIG). Through controlling the spin current injection by altering the Py-YIG interface, we have isolated the spin current contribution and demonstrated the ISHE in a ferromagnetic metal, the reciprocal phenomenon of the anomalous Hall effect. A large spin Hall angle in Py, determined from Py thin films of different thicknesses, indicates many other ferromagnetic metals may be exploited as superior pure spin current detectors and for applications in spin current.

Neutron time-of-flight spectra from inertial confinement fusion experiments with tritium-filled targets have been measured at the National Ignition Facility. These spectra represent a significant improvement in energy resolution and statistics over previous measurements, and afford the first definitive observation of a peak resulting from sequential decay through the ground state of ${}^5\mathrm{He}$ at low reaction energies $E_{\mathrm{c}.\mathrm{m}.}\lesssim 100\mathrm{keV}$. To describe the spectrum, we have developed an $R$-matrix model that accounts for interferences from fermion symmetry and intermediate states, and show these effects to be non-negligible. We also find the spectrum can be described by sequential decay through $\ell =1$ states in ${}^5\mathrm{He}$, which differs from previous interpretations.

Here we address the old question in aeolian particle transport about the role of midair collisions. We find that, surprisingly, these collisions do enhance the overall flux substantially. The effect depends strongly on restitution coefficient and wind speed. We can explain this observation as a consequence of a soft bed of grains which floats above the ground and reflects the highest flying particles. We make the unexpected observation that the flux is maximized at an intermediate restitution coefficient of about 0.7, which is comparable to values experimentally measured for collisions between sand grains.

We analyze theoretically and experimentally the existence of a magic frequency for which the absorption of a linearly polarized light beam by a vapor of alkali-metal atoms is independent of the population distribution among the Zeeman sublevels and the angle between the beam and a magnetic field. The phenomenon originates from a peculiar cancellation of the contributions of higher moments of the atomic density matrix, and is described using the Wigner-Eckart theorem and inherent properties of Clebsch-Gordan coefficients. One important application is the robust measurement of the hyperfine population.

We measure the critical scattering length for the appearance of the first three-body bound state, or Efimov three-body parameter, at seven different Feshbach resonances in ultracold ${}^{39}\mathrm{K}$ atoms. We study both intermediate and narrow resonances, where the three-body spectrum is expected to be determined by the nonuniversal coupling of two scattering channels. Instead, our observed ratio of the three-body parameter with the van der Waals radius is approximately the same universal ratio as for broader resonances. This unexpected observation suggests the presence of a new regime for three-body scattering at narrow resonances.

Extremely large magnetoresistance is realized in the nonmagnetic layered metal ${\mathrm{PdCoO}}_2$. In spite of a highly conducting metallic behavior with a simple quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance reaches up to 35 000% for the field along the $[1\overline{1}0]$ direction. Furthermore, the temperature dependence of the resistance becomes nonmetallic for this field direction, while it remains metallic for fields along the [110] direction. Such severe and anisotropic destruction of the interlayer coherence by a magnetic field on a simple Fermi surface is ascribable to orbital motion of carriers on the Fermi surface driven by the Lorentz force, but seems to have been largely overlooked until now.

We study nonequilibrium dynamics for an ensemble of tilted one-dimensional atomic Bose-Hubbard chains after a sudden quench to the vicinity of the transition point of the Ising paramagnetic to antiferromagnetic quantum phase transition. The quench results in coherent oscillations for the orientation of effective Ising spins, detected via oscillations in the number of doubly occupied lattice sites. We characterize the quench by varying the system parameters. We report significant modification of the tunneling rate induced by interactions and show clear evidence for collective effects in the oscillatory response.

Experimental observation of excited state exciton Rabi rotation in a single GaN quantum dot is presented. The dot is embedded in a site-controlled $\mathrm{GaN}/\mathrm{AlGaN}$ nanowire. Damped oscillation is observed in the power-dependent spectra of the quantum-dot ground state upon resonant pumping of an excited state that had been identified by photoluminescence excitation spectroscopy. A discussion on the origins of the damping is given.

We report a joint test of local Lorentz invariance and the Einstein equivalence principle for electrons, using long-term measurements of the transition frequency between two nearly degenerate states of atomic dysprosium. We present many-body calculations which demonstrate that the energy splitting of these states is particularly sensitive to violations of both special and general relativity. We limit Lorentz violation for electrons at the level of ${10}^{-17}$, matching or improving the best laboratory and astrophysical limits by up to a factor of 10, and improve bounds on gravitational redshift anomalies for electrons by 2 orders of magnitude, to ${10}^{-8}$. With some enhancements, our experiment may be sensitive to Lorentz violation at the level of $9\times {10}^{-20}$.

Magnetic fields appear to be present in all galaxies and galaxy clusters. Recent measurements indicate that a weak magnetic field may be present even in the smooth low density intergalactic medium. One explanation for these observations is that a seed magnetic field was generated by some unknown mechanism early in the life of the Universe, and was later amplified by various dynamos in nonlinear objects like galaxies and clusters. We show that a primordial magnetic field is expected to be generated in the early Universe on purely linear scales through vorticity induced by scale-dependent temperature fluctuations, or equivalently, a spatially varying speed of sound of the gas. Residual free electrons left over after recombination tap into this vorticity to generate magnetic field via the Biermann battery process. Although the battery operates even in the absence of any relative velocity between dark matter and gas at the time of recombination, the presence of such a relative velocity modifies the predicted spatial power spectrum of the magnetic field. At redshifts of order a few tens, we estimate a root mean square field strength of order ${10}^{-25}–{10}^{-24}\mathrm{G}$ on comoving scales $\sim 10\mathrm{kpc}$. This field, which is generated purely from linear perturbations, is expected to be amplified significantly after reionization, and to be further boosted by dynamo processes during nonlinear structure formation.

We have obtained experimental photo-double- and photo-triple-detachment cross sections for the fullerene negative ion using Advanced Light Source photons of 17–90 eV. The cross sections are 2 and 2.5 times larger than those for ${\mathrm{C}}_{60}$ and appear to be compressed and shifted in photon energy as compared to ${\mathrm{C}}_{60}$. Our analysis reveals that the additional electron in $\mathrm{C}_{60}{}^{-}$ primarily produces screening which is responsible for the modification of the spectrum. Both screening effects, the shift and the compression, can be quantitatively accounted for by a linear transformation of the energy axis. Applying the transformation allows us to map the neutral and negative ion cross sections onto each other, pointing out the close relationship of correlated few-electron dynamics in neutral and negatively charged extended systems. In contrast, dynamics of neutral and negatively charged atoms or small molecules are typically not closely related.

An all-electronic physical random number generator at rates up to $80\mathrm{Gbit}/\mathrm{s}$ is presented, based on weakly coupled $\mathrm{GaAs}/{\mathrm{Ga}}_{0.55}{\mathrm{Al}}_{0.45}\mathrm{As}$ superlattices operated at room temperature. It is based on large-amplitude, chaotic current oscillations characterized by a bandwidth of several hundred MHz and do not require external feedback or conversion to an electronic signal prior to digitization. The method is robust and insensitive to external perturbations and its fully electronic implementation suggests scalability and minimal postprocessing in comparison to existing optical implementations.

We propose a novel chiral order parameter to explain the unusual polar Kerr effect in underdoped cuprates. It is based on the loop-current model by Varma, which is characterized by the in-plane anapole moment $\mathit{N}$ and exhibits the magnetoelectric effect. We propose a helical structure where the vector ${\mathit{N}}^{(n)}$ in the layer $n$ is twisted by the angle $\pi /2$ relative to ${\mathit{N}}^{(n-1)}$, thus breaking inversion symmetry. We show that coupling between magnetoelectric terms in the neighboring layers for this structure produces optical gyrotropy, which results in circular dichroism and the polar Kerr effect.

The interaction of a solitary wave with an interface formed by two strongly nonlinear noncohesive granular lattices displays rich behavior, characterized by the breakdown of continuum equations of motion in the vicinity of the interface. By treating the solitary wave as a quasiparticle with an effective mass, we construct an intuitive (energy- and linear-momentum-conserving) discrete model to predict the amplitudes of the transmitted solitary waves generated when an incident solitary-wave front, parallel to the interface, moves from a denser to a lighter granular hexagonal lattice. Our findings are corroborated with simulations. We then successfully extend this model to oblique interfaces, where we find that the angle of refraction and reflection of a solitary wave follows, below a critical value, an analogue of Snell’s law in which the solitary-wave speed replaces the speed of sound, which is zero in the sonic vacuum.

Bohr proposed that the outcome of a measurement becomes objective and real, and, hence, classical, when its results can be communicated by classical means. In this work we revisit Bohr’s postulate using modern tools from quantum information theory. We find a full confirmation of Bohr’s idea: if a measurement device is in a nonclassical state, the measurement results cannot be communicated perfectly by classical means. In this case some part of the information in the measurement apparatus is lost in the process of communication: the amount of this lost information turns out to be the quantum discord. The information loss occurs even when the apparatus is not entangled with the system of interest. The tools presented in this work allow us to generalize Bohr’s postulate: we show that for pure system-apparatus states quantum communication does not provide any advantage when measurement results are communicated to more than one recipient. We further demonstrate the superiority of quantum communication to two recipients on a mixed system-apparatus state and show that this effect is fundamentally different from quantum state cloning.

The resolving power of an electron microscope is determined by the optics and the stability of the instrument. Recently, progress has been obtained towards subångström resolution at beam energies of 80 kV and below but a discrepancy between the expected and achieved instrumental information limit has been observed. Here we show that magnetic field noise from thermally driven currents in the conductive parts of the instrument is the root cause for this hitherto unexplained decoherence phenomenon. We demonstrate that the deleterious effect depends on temperature and at least weakly on the type of material.

We measure the interdot charge relaxation time $T_1$ of a single electron trapped in an accumulation mode $\mathrm{Si}/\mathrm{SiGe}$ double quantum dot. The energy level structure of the charge qubit is determined using photon assisted tunneling, which reveals the presence of a low-lying excited state. We systematically measure $T_1$ as a function of detuning and interdot tunnel coupling and show that it is tunable over four orders of magnitude, with a maximum of $45\mu \mathrm{s}$ for our device configuration.

We describe a simple and solvable model of a device that—like the “neat-fingered being” in Maxwell’s famous thought experiment—transfers energy from a cold system to a hot system by rectifying thermal fluctuations. In order to accomplish this task, our device requires a memory register to which it can write information: the increase in the Shannon entropy of the memory compensates the decrease in the thermodynamic entropy arising from the flow of heat against a thermal gradient. We construct the nonequilibrium phase diagram for this device, and find that it can alternatively act as an eraser of information. We discuss our model in the context of the second law of thermodynamics.