The rotation curves of spiral galaxies exhibit a diversity that has been difficult to understand in the cold dark matter (CDM) paradigm. We show that the self-interacting dark matter (SIDM) model provides excellent fits to the rotation curves of a sample of galaxies with asymptotic velocities in the $25–300\mathrm{km}/\mathrm{s}$ range that exemplify the full range of diversity. We assume only the halo concentration-mass relation predicted by the CDM model and a fixed value of the self-interaction cross section. In dark-matter-dominated galaxies, thermalization due to self-interactions creates large cores and reduces dark matter densities. In contrast, thermalization leads to denser and smaller cores in more luminous galaxies and naturally explains the flatness of rotation curves of the highly luminous galaxies at small radii. Our results demonstrate that the impact of the baryons on the SIDM halo profile and the scatter from the assembly history of halos as encoded in the concentration-mass relation can explain the diverse rotation curves of spiral galaxies.

Spontaneous collapse models predict that a weak force noise acts on any mechanical system, as a consequence of the collapse of the wave function. Significant upper limits on the collapse rate have been recently inferred from precision mechanical experiments, such as ultracold cantilevers and the space mission LISA Pathfinder. Here, we report new results from an experiment based on a high-$Q$ cantilever cooled to millikelvin temperatures, which is potentially able to improve the current bounds on the continuous spontaneous localization (CSL) model by 1 order of magnitude. High accuracy measurements of the cantilever thermal fluctuations reveal a nonthermal force noise of unknown origin. This excess noise is compatible with the CSL heating predicted by Adler. Several physical mechanisms able to explain the observed noise have been ruled out.

Quantum teleportation, the process by which Alice can transfer an unknown quantum state to Bob by using preshared entanglement and classical communication, is one of the cornerstones of quantum information. The standard benchmark for certifying quantum teleportation consists in surpassing the maximum average fidelity between the teleported and the target states that can be achieved classically. According to this figure of merit, not all entangled states are useful for teleportation. Here we propose a new benchmark that uses the full information available in a teleportation experiment and prove that all entangled states can implement a quantum channel which cannot be reproduced classically. We introduce the idea of nonclassical teleportation witness to certify if a teleportation experiment is genuinely quantum and discuss how to quantify this phenomenon. Our work provides new techniques for studying teleportation that can be immediately applied to certify the quality of quantum technologies.

A highly significant structure is observed in the ${\mathrm{\Lambda }}_c^{+}{K}^{-}{\pi }^{+}{\pi }^{+}$ mass spectrum, where the ${\mathrm{\Lambda }}_c^{+}$ baryon is reconstructed in the decay mode $p{K}^{-}{\pi }^{+}$. The structure is consistent with originating from a weakly decaying particle, identified as the doubly charmed baryon ${\mathrm{\Xi }}_{cc}^{++}$. The difference between the masses of the ${\mathrm{\Xi }}_{cc}^{++}$ and ${\mathrm{\Lambda }}_c^{+}$ states is measured to be $1334.94\pm 0.72(\text{stat.})\pm 0.27(\text{syst}\mathrm{.})\mathrm{MeV}/c^2$, and the ${\mathrm{\Xi }}_{cc}^{++}$ mass is then determined to be $3621.40\pm 0.72(\text{stat.})\pm 0.27(\text{syst}\mathrm{.})\pm 0.14({\mathrm{\Lambda }}_c^{+})\mathrm{MeV}/c^2$, where the last uncertainty is due to the limited knowledge of the ${\mathrm{\Lambda }}_c^{+}$ mass. The state is observed in a sample of proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $1.7{\mathrm{fb}}^{-1}$, and confirmed in an additional sample of data collected at 8 TeV.

We present a lattice determination of the $\mathrm{\Lambda }$ parameter in three-flavor QCD and the strong coupling at the $Z$ pole mass. Computing the nonperturbative running of the coupling in the range from 0.2 to 70 GeV, and using experimental input values for the masses and decay constants of the pion and the kaon, we obtain ${\mathrm{\Lambda }}_{\overline{\mathrm{MS}}}^{(3)}=341(12)\mathrm{MeV}$. The nonperturbative running up to very high energies guarantees that systematic effects associated with perturbation theory are well under control. Using the four-loop prediction for ${\mathrm{\Lambda }}_{\overline{\mathrm{MS}}}^{(5)}/{\mathrm{\Lambda }}_{\overline{\mathrm{MS}}}^{(3)}$ yields ${\alpha }_{\overline{\mathrm{MS}}}^{(5)}(m_Z)=0.11852(84)$.

The impact of a highly charged ion onto a solid gives rise to charge exchange between the ion and target atoms, so that a slow ion gets neutralized in the vicinity of the surface. Using highly charged Ar and Xe ions and the surface-only material graphene as a target, we show that the neutralization and deexcitation of the ions proceeds on a sub-10 fs time scale. We further demonstrate that a multiple Interatomic Coulombic Decay (ICD) model can describe the observed ultrafast deexcitation. Other deexcitation mechanisms involving nonradiative decay and quasimolecular orbital formation during the impact are not important, as follows from the comparison of our experimental data with the results of first-principles calculations. Our method also enables the estimation of ICD rates directly.

Negative longitudinal magnetoresistance (NLMR) is shown to occur in topological materials in the extreme quantum limit, when a magnetic field is applied parallel to the excitation current. We perform pulsed and dc field measurements on ${\mathrm{Pb}}_{1-\mathrm{x}}{\mathrm{Sn}}_{\mathrm{x}}\mathrm{Se}$ epilayers where the topological state can be chemically tuned. The NLMR is observed in the topological state, but is suppressed and becomes positive when the system becomes trivial. In a topological material, the lowest $N=0$ conduction Landau level disperses down in energy as a function of increasing magnetic field, while the $N=0$ valence Landau level disperses upwards. This anomalous behavior is shown to be responsible for the observed NLMR. Our work provides an explanation of the outstanding question of NLMR in topological insulators and establishes this effect as a possible hallmark of bulk conduction in topological matter.

Room-temperature superconductivity has been a long-held dream and an area of intensive research. Recent experimental findings of superconductivity at 200 K in highly compressed hydrogen (H) sulfides have demonstrated the potential for achieving room-temperature superconductivity in compressed H-rich materials. We report first-principles structure searches for stable H-rich clathrate structures in rare earth hydrides at high pressures. The peculiarity of these structures lies in the emergence of unusual H cages with stoichiometries ${\mathrm{H}}_{24}$, ${\mathrm{H}}_{29}$, and ${\mathrm{H}}_{32}$, in which H atoms are weakly covalently bonded to one another, with rare earth atoms occupying the centers of the cages. We have found that high-temperature superconductivity is closely associated with H clathrate structures, with large H-derived electronic densities of states at the Fermi level and strong electron-phonon coupling related to the stretching and rocking motions of H atoms within the cages. Strikingly, a yttrium (Y) ${\mathrm{H}}_{32}$ clathrate structure of stoichiometry ${\mathrm{YH}}_{10}$ is predicted to be a potential room-temperature superconductor with an estimated $T_c$ of up to 303 K at 400 GPa, as derived by direct solution of the Eliashberg equation.

We investigate the behavior of droplets and soft elastic objects propelled with a catapult. Experiments show that the ejection velocity depends on both the projectile deformation and the catapult acceleration dynamics. With a subtle matching given by a peculiar value of the projectile/catapult frequency ratio, a 250% kinetic energy gain is obtained as compared to the propulsion of a rigid projectile with the same engine. This superpropulsion has strong potentialities: actuation of droplets, sorting of objects according to their elastic properties, and energy saving for propulsion engines.

To provide insights into the stabilizing mechanisms of trimethylamine-$N$-oxide (TMAO) on protein structures, we perform all-atom molecular dynamics simulations of peptides and the Trp-cage miniprotein. The effects of TMAO on the backbone and charged residues of peptides are found to stabilize compact conformations, whereas effects of TMAO on nonpolar residues lead to peptide swelling. This suggests competing mechanisms of TMAO on proteins, which accounts for hydrophobic swelling, backbone collapse, and stabilization of charge-charge interactions. These mechanisms are observed in Trp cage.

Two basic lattice distortions permeate the structural phase diagram of oxide perovskites: antiferrodistortive (AFD) rotations and tilts of the oxygen octahedral network and polar ferroelectric modes. With some notable exceptions, these two order parameters rarely coexist in a bulk crystal, and understanding their competition is a lively area of active research. Here we demonstrate, by using the ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ system as a test case, that quantum confinement can be a viable tool to shift the balance between AFD and polar modes and selectively stabilize one of the two phases. By combining scanning transmission electron microscopy (STEM) and first-principles-based models, we find a crossover between a bulklike ${\mathrm{LaAlO}}_3$ structure where AFD rotations prevail, to a strongly polar state with no AFD tilts at a thickness of approximately three unit cells; therefore, in addition to the celebrated electronic reconstruction, our work unveils a second critical thickness, related not to the electronic properties but to the structural ones. We discuss the implications of these findings, both for the specifics of the ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ system and for the general quest towards nanoscale control of material properties.

The mean-field treatment of the Bose-Hubbard model predicts properties of lattice-trapped gases to be insensitive to the specific lattice geometry once system energies are scaled by the lattice coordination number $z$. We test this scaling directly by comparing coherence properties of ${}^{87}\mathrm{Rb}$ gases that are driven across the superfluid to Mott insulator transition within optical lattices of either the kagome ($z=4$) or the triangular ($z=6$) geometries. The coherent fraction measured for atoms in the kagome lattice is lower than for those in a triangular lattice with the same interaction and tunneling energies. A comparison of measurements from both lattices agrees quantitatively with the scaling prediction. We also study the response of the gas to a change in lattice geometry, and observe the dynamics as a strongly interacting kagome-lattice gas is suddenly “hole doped” by introducing the additional sites of the triangular lattice.

${{}^{133}\mathrm{Ba}}^{+}$ has been identified as an attractive ion for quantum information processing due to the unique combination of its spin-$1/2$ nucleus and visible wavelength electronic transitions. Using a microgram source of radioactive material, we trap and laser cool the synthetic $A=133$ radioisotope of barium II in a radio-frequency ion trap. Using the same, single trapped atom, we measure the isotope shifts and hyperfine structure of the $6^2{P}_{1/2}\leftrightarrow 6^2{S}_{1/2}$ and $6^2{P}_{1/2}\leftrightarrow 5^2{D}_{3/2}$ electronic transitions that are needed for laser cooling, state preparation, and state detection of the clock-state hyperfine and optical qubits. We also report the $6^2{P}_{1/2}\leftrightarrow 5^2{D}_{3/2}$ electronic transition isotope shift for the rare $A=130$ and 132 barium nuclides, completing the spectroscopic characterization necessary for laser cooling all long-lived barium II isotopes.

We demonstrate significantly improved magneto-optical trapping of molecules using a very slow cryogenic beam source and either rf modulated or dc magnetic fields. The rf magneto-optical trap (MOT) confines $1.0(3)\times {10}^5$ CaF molecules at a density of $7(3)\times {10}^6{\mathrm{cm}}^{-3}$, which is an order of magnitude greater than previous molecular MOTs. Near Doppler-limited temperatures of $340(20)\mu \mathrm{K}$ are attained. The achieved density enables future work to directly load optical tweezers and create optical arrays for quantum simulation.

Despite the dramatic increase of viscosity as temperature decreases, some glasses are known to feature room-temperature relaxation. However, the structural origin of this phenomenon—known as the “thermometer effect”—remains unclear. Here, based on accelerated molecular dynamics simulations of alkali silicate glasses, we show that both enthalpy and volume follow stretched exponential decay functions upon relaxation. However, we observe a bifurcation of their stretching exponents, with $\beta =3/5$ and $3/7$ for enthalpy and volume relaxation, respectively, in agreement with Phillips’s topological diffusion-trap model. Based on these results, we demonstrate that the thermometer effect is a manifestation of the mixed alkali effect. We show that relaxation is driven by the existence of stressed local structural instabilities in mixed alkali glasses. This driving force is found to be at a maximum when the concentrations of each alkali atom equal each other, which arises from a balance between the concentration of each alkali atom and the magnitude of the local stress that they experience.

Birefringence in stable glasses produced by physical vapor deposition often implies molecular alignment similar to liquid crystals. As such, it remains unclear whether these glasses share the same energy landscape as liquid-quenched glasses that have been aged for millions of years. Here, we produce stable glasses of 9-(3,5-di(naphthalen-1-yl)phenyl)anthracene molecules that retain three-dimensional shapes and do not preferentially align in a specific direction. Using a combination of angle- and polarization-dependent photoluminescence and ellipsometry experiments, we show that these stable glasses possess a predominantly isotropic molecular orientation while being optically birefringent. The intrinsic birefringence strongly correlates with increased density, showing that molecular ordering is not required to produce stable glasses or optical birefringence, and provides important insights into the process of stable glass formation via surface-mediated equilibration. To our knowledge, such novel amorphous packing has never been reported in the past.

The cobra wave is a popular physical phenomenon arising from the explosion of a metastable grillage made of popsicle sticks. The sticks are expelled from the mesh by releasing the elastic energy stored during the weaving of the structure. Here we analyze both experimentally and theoretically the propagation of the wave front depending on the properties of the sticks and the pattern of the mesh. We show that its velocity and its shape are directly related to the recoil imparted to the structure by the expelled sticks. Finally, we show that the cobra wave can only exist for a narrow range of parameters constrained by gravity and rupture of the sticks.

The conversion of charge currents into spin currents in nonmagnetic conductors is a hallmark manifestation of spin-orbit coupling that has important implications for spintronic devices. Here we report the measurement of the interfacial spin accumulation induced by the spin Hall effect in Pt and W thin films using magneto-optical Kerr microscopy. We show that the Kerr rotation has opposite sign in Pt and W and scales linearly with current density. By comparing the experimental results with ab initio calculations of the spin Hall and magneto-optical Kerr effects, we quantitatively determine the current-induced spin accumulation at the Pt interface as $5\times {10}^{-12}{\mu }_B{\mathrm{A}}^{-1}{\mathrm{cm}}^2$ per atom. From thickness-dependent measurements, we determine the spin diffusion length in a single Pt film to be $11\pm 3\mathrm{nm}$, which is significantly larger compared to that of Pt adjacent to a magnetic layer.

The production of jets in association with $Z$ bosons, reconstructed via the ${\mu }^{+}{\mu }^{-}$ and $e^{+}{e}^{-}$ decay channels, is studied in $pp$ and, for the first time, in Pb-Pb collisions. Both data samples were collected by the CMS experiment at the LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The Pb-Pb collisions were analyzed in the 0%–30% centrality range. The back-to-back azimuthal alignment was studied in both $pp$ and Pb-Pb collisions for $Z$ bosons with transverse momentum $p_{\mathrm{T}}^Z>60\mathrm{GeV}/c$ and a recoiling jet with $p_{\mathrm{T}}^{\text{jet}}>30\mathrm{GeV}/c$. The $p_{\mathrm{T}}$ imbalance $x_{jZ}=p_{\mathrm{T}}^{\text{jet}}/p_{\mathrm{T}}^Z$, as well as the average number of jet partners per $Z$, $R_{jZ}$, was studied in intervals of $p_{\mathrm{T}}^Z$. The $R_{jZ}$ is found to be smaller in Pb-Pb than in $pp$ collisions, which suggests that in Pb-Pb collisions a larger fraction of partons associated with the $Z$ bosons fall below the $30\mathrm{GeV}/c$ $p_{\mathrm{T}}^{\text{jet}}$ threshold because they lose energy.

The theory of phase transitions represents a central concept for the characterization of equilibrium matter. In this work we study experimentally an extension of this theory to the nonequilibrium dynamical regime termed dynamical quantum phase transitions (DQPTs). We investigate and measure DQPTs in a string of ions simulating interacting transverse-field Ising models. During the nonequilibrium dynamics induced by a quantum quench we show for strings of up to 10 ions the direct detection of DQPTs by revealing nonanalytic behavior in time. Moreover, we provide a link between DQPTs and the dynamics of other quantities such as the magnetization, and we establish a connection between DQPTs and entanglement production.