We investigate the discovery potential of semileptonic hyperon decays in terms of searches of new physics at teraelectronvolt scales. These decays are controlled by a small $SU(3)$-flavor breaking parameter that allows for systematic expansions and accurate predictions in terms of a reduced dependence on hadronic form factors. We find that muonic modes are very sensitive to nonstandard scalar and tensor contributions and demonstrate that these could provide a powerful synergy with direct searches of new physics at the LHC.

Differences in plasticity are usually attributed to significant changes in crystalline symmetry or the strength of the interatomic bonds. In the $B1$ monocarbides, differences in slip planes exist at low temperatures despite having the same structure and very similar bonding characteristics. Our experimental results demonstrate concretely that HfC slips on $\{110\}$ planes while TaC slips on $\{111\}$ planes. Density functional theory calculations rationalize this difference through the formation of an intrinsic stacking fault on the $\{111\}$ planes, formation of Shockley partials, and enhanced metallic bonding because of the valence filling of electrons between these transitional metal carbides.

Atomic resolution at a low accelerating voltage with aberration correction is required to reduce the electron irradiation damage in scanning transmission electron microscopy imaging. However, the reduction in resolution caused by the diffraction limit becomes severe with increasing electron wavelength at low accelerating voltages. The developed aberration corrector can compensate for higher-order aberration in scanning transmission electron microscopy to expand the uniform phase angle. The resolution for imaging graphene at 30 kV is evaluated by changing the convergence angle for a probe-forming system with a higher-order aberration corrector. A single-carbon atom on graphene is successfully imaged at atomic resolution with a cold-field emission gun by dark-field imaging at an accelerating voltage of 30 kV.

The determination of spectral properties from first principles can provide powerful connections between microscopic theoretical predictions and experimental data, but requires complex electronic-structure formulations that fall outside the domain of applicability of common approaches, such as density-functional theory. We show here that Koopmans-compliant functionals, constructed to enforce piecewise linearity and the correct discontinuity derivative in energy functionals with respect to fractional occupation—i.e., with respect to charged excitations—provide molecular photoemission spectra and momentum maps of Dyson orbitals that are in excellent agreement with experimental ultraviolet photoemission spectroscopy and orbital tomography data. These results highlight the role of Koopmans-compliant functionals as accurate and inexpensive quasiparticle approximations to the spectral potential.

We consider a normal lead coupled to a Majorana bound state. We show that the spin-resolved current correlations exhibit unique features which distinguish Majorana bound states from other low-energy resonances. In particular, the spin-up and spin-down currents from a Majorana bound state are anticorrelated at low bias voltages, and become uncorrelated at higher voltages. This behavior is independent of the exact form of coupling to the lead, and of the direction of the spin polarization. In contrast, an ordinary low-energy Andreev bound state gives rise to a positive correlation between the spin-up and spin-down currents, and this spin-resolved current-current correlation approaches a nonzero constant at high bias voltages. We discuss experimental setups in which this effect can be measured.

We explore the high-temperature dynamics of the disordered, one-dimensional $XXZ$ model near the many-body localization (MBL) transition, focusing on the delocalized (i.e., “metallic”) phase. In the vicinity of the transition, we find that this phase has the following properties: (i) local magnetization fluctuations relax subdiffusively; (ii) the ac conductivity vanishes near zero frequency as a power law; and (iii) the distribution of resistivities becomes increasingly broad at low frequencies, approaching a power law in the zero-frequency limit. We argue that these effects can be understood in a unified way if the metallic phase near the MBL transition is a quantum Griffiths phase. We establish scaling relations between the associated exponents, assuming a scaling form of the spin-diffusion propagator. A phenomenological classical resistor-capacitor model captures all the essential features.

The data analysis of the gravitational wave signals emitted by coalescing neutron star binaries requires the availability of an accurate analytical representation of the dynamics and waveforms of these systems. We propose an effective-one-body model that describes the general relativistic dynamics of neutron star binaries from the early inspiral up to the merger. Our effective-one-body model incorporates an enhanced attractive tidal potential motivated by recent analytical advances in the post-Newtonian and gravitational self-force description of relativistic tidal interactions. No fitting parameters are introduced for the description of tidal interaction in the late, strong-field dynamics. We compare the model energetics and the gravitational wave phasing with new high-resolution multiorbit numerical relativity simulations of equal-mass configurations with different equations of state. We find agreement within the uncertainty of the numerical data for all configurations. Our model is the first semianalytical model that captures the tidal amplification effects close to merger. It thereby provides the most accurate analytical representation of binary neutron star dynamics and waveforms currently available.

We use the magnetic field distribution of an azimuthally polarized focused laser beam to excite a magnetic dipole transition in ${\mathrm{Eu}}^{3+}$ ions embedded in a ${\mathrm{Y}}_2{\mathrm{O}}_3$ nanoparticle. The absence of the electric field at the focus of an azimuthally polarized beam allows us to unambiguously demonstrate that the nanoparticle is excited by the magnetic dipole transition near 527.5 nm. When the laser wavelength is resonant with the magnetic dipole transition, the nanoparticle maps the local magnetic field distribution, whereas when the laser wavelength is resonant with an electric dipole transition, the nanoparticle is sensitive to the local electric field. Hence, by tuning the excitation wavelength, we can selectively excite magnetic or electric dipole transitions through optical fields.

In many of the experimental systems that may host Majorana zero modes, a so-called chiral symmetry exists that protects overlapping zero modes from splitting up. This symmetry is operative in a superconducting nanowire that is narrower than the spin-orbit scattering length, and at the Dirac point of a superconductor-topological insulator heterostructure. Here we show that chiral symmetry strongly modifies the dynamical and spectral properties of a chaotic scatterer, even if it binds only a single zero mode. These properties are quantified by the Wigner-Smith time-delay matrix $Q=-i\hslash S^{†}dS/dE$, the Hermitian energy derivative of the scattering matrix, related to the density of states by $\rho =(2\pi \hslash {)}^{-1}\mathrm{Tr}Q$. We compute the probability distribution of $Q$ and $\rho$, dependent on the number $\nu$ of Majorana zero modes, in the chiral ensembles of random-matrix theory. Chiral symmetry is essential for a significant $\nu$ dependence.

High-resolution angle-resolved photoelectron spectroscopy is used to examine the electronic band structure of ${\mathrm{FeTe}}_{0.5}{\mathrm{Se}}_{0.5}$ near the Brillouin zone center. A consistent separation of the ${\alpha }_1$ and ${\alpha }_2$ bands is observed with little $k_z$$$ dependence of the ${\alpha }_1$ band. First-principles calculations for bulk and thin films demonstrate that the antiferromagnetic coupling between the Fe atoms and hybridization-induced spin-orbit effects lifts the degeneracy of the Fe $d_{xz}$ and $d_{yz}$ orbitals at the zone center leading to orbital ordering. These experimental and computational results provide a natural microscopic basis for the nematicity observed in the Fe-based superconductors.

We describe far-from-equilibrium nonlocal transport in a diffusive superconducting wire with a Zeeman splitting, taking into account different spin relaxation mechanisms. We demonstrate that due to the Zeeman splitting, an injection of current in a superconducting wire creates spin accumulation that can only relax via thermalization. This effect leads to a long-range spin accumulation detectable in the nonlocal signal. Our model gives a qualitative explanation and provides accurate fits of recent experimental results in terms of realistic parameters.

We propose the $\pi$ flux triangular lattice Hubbard model ($\pi$ THM) as a prototypical setup to stabilize magnetically disordered quantum states of matter in the presence of charge fluctuations. The quantum paramagnetic domain of the $\pi$ THM that we identify for intermediate Hubbard $U$ is framed by a Dirac semimetal for weak coupling and by 120° Néel order for strong coupling. Generalizing the Klein duality from spin Hamiltonians to tight-binding models, the $\pi$ THM maps to a Hubbard model which corresponds to the $(J_{\mathrm{H}},J_{\mathrm{K}})=(-1,2)$ Heisenberg-Kitaev model in its strong coupling limit. The $\pi$ THM provides a promising microscopic testing ground for exotic finite-$U$ spin liquid ground states amenable to numerical investigation.

Correlations that violate a Bell inequality are said to be nonlocal; i.e., they do not admit a local and deterministic explanation. Great effort has been devoted to study how the amount of nonlocality (as measured by a Bell inequality violation) serves to quantify the amount of randomness present in observed correlations. In this work we reverse this research program and ask what do the randomness certification capabilities of a theory tell us about the nonlocality of that theory. We find that, contrary to initial intuition, maximal randomness certification cannot occur in maximally nonlocal theories. We go on and show that quantum theory, in contrast, permits certification of maximal randomness in all dichotomic scenarios. We hence pose the question of whether quantum theory is optimal for randomness; i.e., is it the most nonlocal theory that allows maximal randomness certification? We answer this question in the negative by identifying a larger-than-quantum set of correlations capable of this feat. Not only are these results relevant to understanding quantum mechanics’ fundamental features, but also put fundamental restrictions on device-independent protocols based on the no-signaling principle.

We report on a new constraint on gravitylike short-range forces, in which the interaction charge is mass, obtained by measuring the angular distribution of 5 Å neutrons scattering off atomic xenon gas. Around $10^7$ scattering events were collected at the 40 m small angle neutron scattering beam line located at the HANARO research reactor of the Korean Atomic Energy Research Institute. The extracted coupling strengths of new forces in the Yukawa-type parametrization are ${\widehat{g}}^2=(0.2\pm 6.8\pm 2.0)\times 10^{-15}{\mathrm{GeV}}^{-2}$ and ${\widehat{g}}^2=(-5.3\pm 9.0_{-2.8}^{+2.7})\times 10^{-17}{\mathrm{GeV}}^{-2}$ for interaction ranges of 0.1 and 1.0 nm, respectively. These strengths correspond to 95% confidence level limits of $g^2<(1.4\pm 0.2)\times 10^{-14}{\mathrm{GeV}}^{-2}$ and $g^2<(1.3\pm 0.2)\times 10^{-16}{\mathrm{GeV}}^{-2}$, improving the current limits for interaction ranges between 4 and 0.04 nm by a factor of up to 10.

Any slight variations in the fundamental constants of nature, which may be induced by dark matter or some yet-to-be-discovered cosmic field, would characteristically alter the phase of a light beam inside an interferometer, which can be measured extremely precisely. Laser and maser interferometry may be applied to searches for the linear-in-time drift of the fundamental constants, detection of topological defect dark matter through transient-in-time effects, and for a relic, coherently oscillating condensate, which consists of scalar dark matter fields, through oscillating effects. Our proposed experiments require either minor or no modifications of existing apparatus, and offer extensive reach into important and unconstrained spaces of physical parameters.

The results of a dedicated search for pair production of scalar partners of charm quarks are reported. The search is based on an integrated luminosity of $20.3{\mathrm{fb}}^{-1}$ of $pp$ collisions at $\sqrt{s}=8\mathrm{TeV}$ recorded with the ATLAS detector at the LHC. The search is performed using events with large missing transverse momentum and at least two jets, where the two leading jets are each tagged as originating from $c$ quarks. Events containing isolated electrons or muons are vetoed. In an $R$-parity-conserving minimal supersymmetric scenario in which a single scalar-charm state is kinematically accessible, and where it decays exclusively into a charm quark and a neutralino, 95% confidence-level upper limits are obtained in the scalar-charm–neutralino mass plane such that, for neutralino masses below 200 GeV, scalar-charm masses up to 490 GeV are excluded.