The role of excess intrinsic atoms for residual point defect balance has been discriminated by implanting Zn or O ions into Li-containing ZnO and monitoring Li redistribution and electrical resistivity after postimplant anneals. Strongly Li-depleted regions were detected in the Zn-implanted samples at depths beyond the projected range ($R_p$) upon annealing $\ge 600°\mathrm{C}$, correlating with a resistivity decrease. In contrast, similar anneals of the O-implanted samples resulted in Li accumulation at $R_p$ and an increased resistivity. Control samples implanted with Ar or Ne ions, yielding similar defect production as for the Zn or O implants but with no surplus of intrinsic atoms, revealed no Li depletion. Thus, the depletion of Li shows evidence of excess Zn interstitials (${\mathrm{Zn}}_I$) being released during annealing of the Zn-implanted samples. These ${\mathrm{Zn}}_I$’s convert substitutional Li atoms (${\mathrm{Li}}_{\mathrm{Zn}}$) into highly mobile interstitial ones leading to the strongly Li-depleted regions. In the O-implanted samples, the high resistivity provides evidence of stable ${\mathrm{O}}_I$-related acceptors.

In this Letter, we investigate the time evolution of the conductivity relaxation process in a prototypical ionic glass former, $[\mathrm{Ca}({\mathrm{NO}}_3{)}_2{]}_{0.4}[{\mathrm{KNO}}_3{]}_{0.6}$ (CKN), undergoing physical aging. It is demonstrated that the heterogeneous nature of molecular dynamics is manifested by an increase in the slope of the high frequency wing of the conductivity relaxation peak as the sample is annealed below the glass transition temperature. This finding is also confirmed for other ionic glass formers. Additionally, we analyze the kinetics of the change in the ionic conductivity in glassy CKN to probe its structural relaxation.

When pure water is cooled at $\sim {10}^6\mathrm{K}/\mathrm{s}$, it forms an amorphous solid (glass) instead of the more familiar crystalline phase. The presence of solutes can reduce this required (or “critical”) cooling rate by orders of magnitude. Here, we present critical cooling rates for a variety of solutes as a function of concentration and a theoretical framework for understanding these rates. For all solutes tested, the critical cooling rate is an exponential function of concentration. The exponential’s characteristic concentration for each solute correlates with the solute’s Stokes radius. A modification of critical droplet theory relates the characteristic concentration to the solute radius and the critical nucleation radius of ice in pure water. This simple theory of ice nucleation and glass formability in aqueous solutions has consequences for general glass-forming systems, and in cryobiology, cloud physics, and climate modeling.

We show that the spin domains, generated in the linear optical spin Hall effect by the analog of spin-orbit interaction for exciton polaritons, are associated with the formation of a Skyrmion lattice. In the nonlinear regime, the spin anisotropy of the polariton-polariton interactions results in a spatial compression of the domains and in a transmutation of the Skyrmions into oblique half-solitons. This phase transition is associated with both the focusing of the spin currents and the emergence of a strongly anisotropic emission pattern.

We experimentally confirmed that the spin-orbit lengths of noble metals obtained from weak antilocalization measurements are comparable to the spin diffusion lengths determined from lateral spin valve ones. Even for metals with strong spin-orbit interactions such as Pt, we verified that the two methods gave comparable values which were much larger than those obtained from recent spin torque ferromagnetic resonance measurements. To give a further evidence for the comparability between the two length scales, we measured the disorder dependence of the spin-orbit length of copper by changing the thickness of the wire. The obtained spin-orbit length nicely follows a linear law as a function of the diffusion coefficient, clearly indicating that the Elliott-Yafet mechanism is dominant as in the case of the spin diffusion length.

Several angle-resolved photoemission spectroscopy (ARPES) studies reveal a poorly nested Fermi surface of LiFeAs, far away from a spin density wave instability, and clear-cut superconducting gap anisotropies. On the other hand a very different, more nested Fermi surface and dissimilar gap anisotropies have been obtained from quasiparticle interference (QPI) data, which were interpreted as arising from intraband scattering within holelike bands. Here we show that this ARPES-QPI paradox is completely resolved by interband scattering between the holelike bands. The resolution follows from an excellent agreement between experimental quasiparticle scattering data and $T$-matrix QPI calculations (based on experimental band structure data), which allows disentangling interband and intraband scattering processes.

Neutron diffraction on the double perovskite ${\mathrm{Sr}}_2{\mathrm{YRuO}}_6$ with a quasi-fcc lattice of Ru moments reveals planar magnetic correlations that condense into a partial long-range ordered state with coupled alternate antiferromagnetic (AFM) ${\mathrm{YRuO}}_4$ square layers coexisting with the short-range correlations below $T_{N1}=32\mathrm{K}$. A second transition to a fully ordered AFM state below $T_{N2}=24\mathrm{K}$ is observed. The reduced dimensionality of the spin correlations is arguably due to a cancellation of the magnetic coupling between consecutive AFM square layers in fcc antiferromagnets, which is the simplest three-dimensional frustrated magnet model system.

Resonant soft-x-ray scattering measurements have been performed to investigate interface electronic structures of (${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$) superlattices. Resonant scattering intensities at superlattice reflections show clear evidence of degeneracy lifting in $t_{2g}$ states of interface Ti ions. Polarization dependence of intensities indicates the energy of $d_{xy}$ states is lower by $\sim 1\mathrm{eV}$ than two other $t_{2g}$ states. The energy splitting is insensitive to epitaxial strain. The orbital reconstruction is induced by oxygen vacancies and confined to the interface within two unit cells, indicating charge compensation at the polar interfaces.

We report ferromagnetic resonance force microscopy of confined spin-wave modes with improved, 100 nm resolution. The ferromagnetic resonance spectra in Permalloy disks (diameters ranging from 100 to 750 nm) distinguish multiple edge modes, and the images reveal distinct precession patterns. The fundamental edge mode also provides a new, localized probe of the magnetic properties of the film edge; rotation of the applied field reveals large edge property variations in nominally circular disks. As a function of disk diameter, the number of observed edge modes agrees with modeling.

We investigate the aging dynamics of amorphous ${\mathrm{SiO}}_2$ via molecular dynamics simulations of a quench from a high temperature $T_i$ to a lower temperature $T_f$. We obtain a microscopic picture of aging dynamics by analyzing single particle trajectories, identifying jump events when a particle escapes the cage formed by its neighbors, and determining how these jumps depend on the waiting time $t_w$, the time elapsed since the temperature quench to $T_f$. We find that the only $t_w$-dependent microscopic quantity is the number of jumping particles per unit time, which decreases with age. Similar to previous studies for fragile glass formers, we show here for the strong glass former ${\mathrm{SiO}}_2$ that neither the distribution of jump lengths nor the distribution of times spent in the cage are $t_w$ dependent. We conclude that the microscopic aging dynamics is surprisingly similar for fragile and strong glass formers.

A hallmark of biopolymer networks is their sensitivity to stress, reflected by pronounced nonlinear elastic stiffening. Here, we demonstrate a distinct dynamical nonlinearity in biopolymer networks consisting of filamentous actin cross-linked by $\alpha$-actinin-4. Applied stress delays the onset of relaxation and flow, markedly enhancing gelation and extending the regime of solidlike behavior to much lower frequencies. We show that this macroscopic network response can be accounted for at the single molecule level by the increased binding affinity of the cross-linker under load, characteristic of catch-bond-like behavior.

Scanning tunneling spectroscopy (STS) allows us to image single molecules decoupled from the supporting substrate. The obtained images are routinely interpreted as the square moduli of molecular orbitals, dressed by the mean-field electron-electron interaction. Here we demonstrate that the effect of electron correlation beyond the mean field qualitatively alters the uncorrelated STS images. Our evidence is based on the ab initio many-body calculation of STS images of planar molecules with metal centers. We find that many-body correlations alter significantly the image spectral weight close to the metal center of the molecules. This change is large enough to be accessed experimentally, surviving to molecule-substrate interactions.

The existence of secondary flows in the pressure-driven flow of a concentrated suspension of noncolloidal particles through a conduit of square cross section under creeping flow conditions is confirmed experimentally. This Letter lends support to the idea that secondary currents, rather than shear-induced migration, may actually be the dominant mechanism that determines particle distribution in noncolloidal suspension flows through nonaxisymmetric geometries. This work also establishes that coextrusion of two concentrated suspensions through nonaxisymmetric geometries with a stable suspension-suspension interface is not possible, except in special situations.

We investigate the role of gravity on convection in a dense granular shear flow. Using a microgravity-modified Taylor-Couette shear cell under the conditions of parabolic flight microgravity, we demonstrate experimentally that secondary, convective-like flows in a sheared granular material are close to zero in microgravity and enhanced under high-gravity conditions, though the primary flow fields are unaffected by gravity. We suggest that gravity tunes the frictional particle-particle and particle-wall interactions, which have been proposed to drive the secondary flow. In addition, the degree of plastic deformation increases with increasing gravitational forces, supporting the notion that friction is the ultimate cause.

Motivated by the recent debate on whether the Kasevich-Chu atom interferometer can measure the gravitational redshift, we show that in different representations of quantum mechanics chosen for the calculation, the observed phase shift appears as though it originates from different physical phenomena. In particular, we demonstrate that the decomposition of the total phase shift into three dynamical phases, which emerges in a semiclassical approach and is at the very heart of the redshift controversy, does not appear in an exact treatment based on a representation-free analysis. Here only two phenomena determine the phase shift: the difference of the laser phases and the acceleration of the atom. Hence, the Kasevich-Chu interferometer is an accelerometer or gravimeter.

The quantum dynamics of a two-state system coupled to a bosonic reservoir with sub-Ohmic spectral density is investigated for strong friction. Numerically exact path integral Monte Carlo methods reveal that a changeover from coherent to incoherent relaxation does not occur for a broad class of spectral distributions. In nonequilibrium coherences associated with substantial system-reservoir entanglement exist even when strong dissipation forces the thermodynamic state of the system to behave almost classically. This may be of relevance for current experiments with nanoscale devices.

A better understanding of the noise causing qubit decoherence is crucial for improving qubit performance. The noise spectrum affecting the qubit may be extracted by measuring dephasing under the application of pulse sequences but requires accurate qubit control and sufficiently long relaxation times, which are not always available. Here, we describe an alternative method to extract the spectrum from correlations of single-shot measurement outcomes of successive free induction decays. This method only requires qubit initialization and readout with a moderate fidelity and also allows independent tuning of both the overall sensitivity and the frequency region over which it is sensitive. Thus, it is possible to maintain a good detection contrast over a very wide frequency range. We discuss using our method for measuring both $1/f$ noise and the fluctuation spectrum of the nuclear bath of GaAs spin qubits.

We introduce the discording power of a unitary transformation, which assesses its capability to produce quantum discord, and analyze in detail the generation of discord by relevant classes of two-qubit gates. Our measure is based on the Cartan decomposition of two-qubit unitaries and on evaluating the maximum discord achievable by a unitary upon acting on classical-classical states at fixed purity. We find that there exist gates which are perfect discorders for any value of purity $\mu$, and that they belong to a class of operators that includes the $\sqrt{\mathrm{SWAP}}$. Other gates, even those universal for quantum computation, do not posses the same property: the CNOT, for example, is a perfect discorder only for states with low or unit purity, but not for intermediate values. The discording power of a two-qubit unitary also provides a generalization of the corresponding measure defined for entanglement to any value of the purity.

We study the fidelity of the surface code in the presence of correlated errors induced by the coupling of physical qubits to a bosonic environment. By mapping the time evolution of the system after one quantum error correction cycle onto a statistical spin model, we show that the existence of an error threshold is related to the appearance of an order-disorder phase transition in the statistical model in the thermodynamic limit. This allows us to relate the error threshold to bath parameters and to the spatial range of the correlated errors.

Device-independent quantum cryptographic schemes aim to guarantee security to users based only on the output statistics of any components used, and without the need to verify their internal functionality. Since this would protect users against untrustworthy or incompetent manufacturers, sabotage, or device degradation, this idea has excited much interest, and many device-independent schemes have been proposed. Here we identify a critical weakness of device-independent protocols that rely on public communication between secure laboratories. Untrusted devices may record their inputs and outputs and reveal information about them via publicly discussed outputs during later runs. Reusing devices thus compromises the security of a protocol and risks leaking secret data. Possible defenses include securely destroying or isolating used devices. However, these are costly and often impractical. We propose other more practical partial defenses as well as a new protocol structure for device-independent quantum key distribution that aims to achieve composable security in the case of two parties using a small number of devices to repeatedly share keys with each other (and no other party).