In collisions of ultrarelativistic nuclei, photon-tagged jets provide a unique opportunity to compare jet production and modification due to parton shower formation and propagation in strongly interacting matter at vastly different center-of-mass energies. We present first results for the cross sections of jets tagged by an isolated photon to $O({\alpha }_{\mathrm{em}}{\alpha }_s^2)$ in central $\mathrm{Au}+\mathrm{Au}$ reactions with $\sqrt{s_{NN}}=200\mathrm{GeV}$ at RHIC and central $\mathrm{Pb}+\mathrm{Pb}$ reactions with $\sqrt{s_{NN}}=2.76\mathrm{TeV}$ at LHC. We evaluate the increase in the transverse momentum imbalance of the observed $\gamma +\mathrm{\text{jet}}$ state, induced by the dissipation of the parton shower energy due to strong final-state interactions. Theoretical predictions to help interpret recent and upcoming experimental data are presented.

Elliptic flow ($v_2$) values for identified particles at midrapidity in $\mathrm{Au}+\mathrm{Au}$ collisions, measured by the STAR experiment in the beam energy scan at RHIC at $\sqrt{s_{NN}}=7.7–62.4\mathrm{GeV}$, are presented. A beam-energy-dependent difference of the values of $v_2$ between particles and corresponding antiparticles was observed. The difference increases with decreasing beam energy and is larger for baryons compared to mesons. This implies that, at lower energies, particles and antiparticles are not consistent with the universal number-of-constituent-quark scaling of $v_2$ that was observed at $\sqrt{s_{NN}}=200\mathrm{GeV}$.

Mutually unbiased bases (MUBs) play a key role in many protocols in quantum science, such as quantum key distribution. However, defining MUBs for arbitrary high-dimensional systems is theoretically difficult, and measurements in such bases can be hard to implement. We show experimentally that efficient quantum state reconstruction of a high-dimensional multipartite quantum system can be performed by considering only the MUBs of the individual parts. The state spaces of the individual subsystems are always smaller than the state space of the composite system. Thus, the benefit of this method is that MUBs need to be defined for the small Hilbert spaces of the subsystems rather than for the large space of the overall system. This becomes especially relevant where the definition or measurement of MUBs for the overall system is challenging. We illustrate this approach by implementing measurements for a high-dimensional system consisting of two photons entangled in the orbital angular momentum degree of freedom, and we reconstruct the state of this system for dimensions of the individual photons from $d=2$ to 5.

Alkaline-earth-metal atoms can exhibit long-range dipolar interactions, which are generated via the coherent exchange of photons on the ${}^{3}P_0-{}^{3}D_1$ transition of the triplet manifold. In the case of bosonic strontium, which we discuss here, this transition has a wavelength of $2.6\mu \mathrm{m}$ and a dipole moment of 4.03 D, and there exists a magic wavelength permitting the creation of optical lattices that are identical for the states ${}^{3}P_0$ and ${}^{3}D_1$. This interaction enables the realization and study of mixtures of hard-core lattice bosons featuring long-range hopping, with tunable disorder and anisotropy. We derive the many-body master equation, investigate the dynamics of excitation transport, and analyze spectroscopic signatures stemming from coherent long-range interactions and collective dissipation. Our results show that lattice gases of alkaline-earth-metal atoms permit the creation of long-lived collective atomic states and constitute a simple and versatile platform for the exploration of many-body systems with long-range interactions. As such, they represent an alternative to current related efforts employing Rydberg gases, atoms with large magnetic moment, or polar molecules.

We report on the dynamic behavior of strongly nonlinear discrete materials with anomalous strain-softening behavior. Rarefaction solitary waves found in numerical calculations agree well with the exact solution to the continuum wave equation. Compression pulses generated by impact quickly disintegrate into a leading rarefaction solitary wave followed by an oscillatory wave train containing localized excitations. Such behavior is favorable for metamaterials design of shock absorption layers as well as tunable information transmission lines for scrambling of acoustic information.

Granular gases are convenient model systems to investigate the statistical physics of nonequilibrium systems. In the literature, one finds numerous theoretical predictions, but only few experiments. We study a weakly excited dilute gas of rods, confined in a cuboid container in microgravity during a suborbital rocket flight. With respect to a gas of spherical grains at comparable filling fraction, the mean free path is considerably reduced. This guarantees a dominance of grain-grain collisions over grain-wall collisions. No clustering was observed, unlike in similar experiments with spherical grains. Rod positions and orientations were determined and tracked. Translational and rotational velocity distributions are non-Gaussian. Equipartition of kinetic energy between translations and rotations is violated.

It is often postulated that quasistatic cracks propagate along the direction allowing fracture for the lowest load. Nevertheless, this statement is debated, in particular for anisotropic materials. We performed tearing experiments in anisotropic brittle thin sheets that validate this principle in the case of weak anisotropy. We also predict the existence of forbidden directions and facets in strongly anisotropic materials, through an analogy with the description of equilibrium shapes in crystals. However, we observe cracks that do not necessarily follow the easiest direction but can select a harder direction, which is only locally more advantageous than neighboring paths. These results challenge the traditional description of fracture propagation, and we suggest a modified, less restrictive criterion compatible with our experimental observations.

We present a scaling theory for the long time behavior of spontaneous imbibition in porous media consisting of interconnected pores with a large length-to-width ratio. At pore junctions, the meniscus propagation in one or more branches can come to a halt when the Laplace pressure of the meniscus exceeds the hydrostatic pressure within the junction. We derive the scaling relations for the emerging arrest time distribution and show that the average front width is proportional to the height, yielding a roughness exponent of exactly $\beta =1/2$ and explaining recent experimental results for nanoporous Vycor glass. Extensive simulations of a pore network model confirm these predictions.

We study the ionization dynamics in intense laser-droplet interaction using three-dimensional, relativistic particle-in-cell simulations. Of particular interest is the laser intensity and frequency regime for which initially transparent, wavelength-sized targets are not homogeneously ionized. Instead, the charge distribution changes both in space and in time on a subcycle scale. One may call this the extreme nonlinear Mie-optics regime. We find that—despite the fact that the plasma created at the droplet surface is overdense—oscillating electric fields may penetrate into the droplet under a certain angle, ionize, and propagate in the just generated plasma. This effect can be attributed to the local field enhancements at the droplet surface predicted by standard Mie theory. The penetration of the fields into the droplet leads to the formation of a highly inhomogeneous charge density distribution in the droplet interior, concentrated mostly in the polarization plane. We present a self-similar, exponential fit of the fractional ionization degree which depends only on a dimensionless combination of electric field amplitude, droplet radius, and plasma frequency with only a weak dependence on the laser frequency in the overdense regime.

The regulation of turbulent transport by zonal flows is studied experimentally on a flux surface of the stellarator experiment TJ-K. Data of 128 Langmuir probes at different toroidal and poloidal positions on a single flux surface enable us to measure simultaneously the zonal flow activity and the turbulent transport in great detail. A reduction of turbulent transport by 30% during the zonal flow phase is found. It is shown that the reduction process is initiated by a modification in the cross phase between density and electric field followed by a reduction in the fluctuation levels, which sustain low transport levels on larger time scales than the zonal flow lifetime.

Rapid electron and ion heating is observed in collisionless counterstreaming plasma flows and explained via a novel heating mechanism that couples the electron and ion temperatures. Recent experiments measure plasma conditions 4 mm from the surface of single foil (single plasma stream) and double foils (two counterstreaming plasmas) targets using Thomson scattering. Significant increases in electron and ion temperatures (from $<100\mathrm{eV}$ to $>1\mathrm{keV}$) compared to the single foil geometry are observed. While electrons are heated by friction on opposite going ions, ion-ion collisions cannot explain the observed ion heating. Also, density and flow velocity measurements show negligible slow down and rule out stagnation. The nonlinear saturation of an acoustic two-stream electrostatic instability is predicted to couple the ion temperature to the electron temperature through the dynamic evolution of the instability threshold. Particle-in-cell simulations including both collisional and collisionless effects are compared to the experimental measurements and show rapid electron and ion heating consistent with the experimental measurements.

We report in this Letter the results of our investigation of 2D Bose gases beyond the dilute limit emphasizing the role played by three-body scattering events. We demonstrate that a competition between three-body attractive interactions and two-body repulsive forces results in the chemical potential of 2D Bose gases to exhibit a maximum at a critical scattering length beyond which these quantum gases possess a negative compressibility. For larger scattering lengths, the increasingly prominent role played by three-body attractive interactions leads to an onset instability at a second critical value. The three-body effects studied here are universal, fully characterized by the effective 2D scattering length $a_{2\mathrm{D}}$ (or the size of the 2D bound states) and are, in comparison to the 3D case, independent of three-body ultraviolet physics. We find, within our approach, the ratios of the contribution to the chemical potential due to three-body interactions to the one due to two-body to be 0.27 near the maximum of the chemical potential and 0.73 in the vicinity of the onset instability.

We prepare and study strongly interacting two-dimensional Bose gases in the superfluid, the classical Berezinskii-Kosterlitz-Thouless (BKT) transition, and the vacuum-to-superfluid quantum critical regimes. A wide range of the two-body interaction strength $0.05<g<3$ is covered by tuning the scattering length and by loading the sample into an optical lattice. Based on the equations of state measurements, we extract the coupling constants as well as critical thermodynamic quantities in different regimes. In the superfluid and the BKT transition regimes, the extracted coupling constants show significant down-shifts from the mean-field and perturbation calculations when $g$ approaches or exceeds one. In the BKT and the quantum critical regimes, all measured thermodynamic quantities show logarithmic dependence on the interaction strength, a tendency confirmed by the extended classical-field and renormalization calculations.

We study the fluctuations of the global velocity $V_l(t)$, computed at various length scales $l$, during the intermittent mode-I propagation of a crack front. The statistics converge to a non-Gaussian distribution, with an asymmetric shape and a fat tail. This breakdown of the central limit theorem (CLT) is due to the diverging variance of the underlying local crack front velocity distribution, displaying a power law tail. Indeed, by the application of a generalized CLT, the full shape of our experimental velocity distribution at large scale is shown to follow the stable Levy distribution, which preserves the power law tail exponent under upscaling. This study aims to demonstrate in general for crackling noise systems how one can infer the complete scale dependence of the activity—and extreme event distributions—by measuring only at a global scale.

We use molecular dynamics simulations to show that glass transition in a model phase separating amorphous alloy, ${\mathrm{Cu}}_{50}{\mathrm{Nb}}_{50}$, occurs by gelation. At the glass transition, a mechanically stiff, percolating network of atoms with icosahedral local packing forms at the interfaces between compositionally enriched regions. This low-energy network halts coarsening of the phase-separated structure and imparts shear resistance. These features of glass transition are remarkably similar to gelation processes in polymeric and colloidal gels.

The water-${\mathrm{TiO}}_2$ interaction is of paramount importance for many processes occurring on ${\mathrm{TiO}}_2$, and the rutile ${\mathrm{TiO}}_2(110)$-($1\times 1$) surface has often been considered as a test case. Yet, no consensus has been reached whether the well-studied surface O vacancies on the terraces are the only active sites for water dissociation on rutile ${\mathrm{TiO}}_2(110)$-($1\times 1$), or whether another channel for the creation of H adatoms exists. Here we use high-resolution scanning tunneling microscopy and density functional theory calculations to tackle this long-standing question. Evidence is presented that a second water dissociation channel exists on the surfaces of vacuum-annealed ${\mathrm{TiO}}_2(110)$ crystals that is associated with the $⟨1\overline{1}1⟩$ step edges. This second water dissociation channel can be suppressed by blocking of the $⟨1\overline{1}1⟩$ step edges using ethanol.

We explain the experimentally observed instability of cold exciton gases and the formation of a macroscopically ordered exciton state in terms of a thermodynamic model accounting for the phase fluctuations of the condensate. We show that the temperature dependence of the exciton energy exhibits fundamental scaling behavior with the signature of the second order phase transition.

Reduced dimensionality has long been regarded as an important strategy for increasing thermoelectric performance, for example, in superlattices and other engineered structures. Here we point out and illustrate by examples that three-dimensional bulk materials can be made to behave as if they were two dimensional from the point of view of thermoelectric performance. Implications for the discovery of new practical thermoelectrics are discussed.

We investigate the transport properties of itinerant electrons interacting with a background of localized spins in a correlated paramagnetic phase of the pyrochlore lattice. We find a residual resistivity at zero temperature due to the scattering of electrons by the static dipolar spin-spin correlation that characterizes the metallic Coulomb phase. As temperature increases, thermally excited topological defects, also known as magnetic monopoles, reduce the spin correlation, hence suppressing electron scattering. Combined with the usual scattering processes in metals at higher temperatures, this mechanism yields a nonmonotonic resistivity, displaying a minimum at temperature scales associated with the magnetic monopole excitation energy. Our calculations agree quantitatively with resistivity measurements in ${\mathrm{Nd}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ and ${\mathrm{Pr}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$, shedding light on the origin of the resistivity minimum observed in metallic spin-ice compounds.

The effect of charge-carrier screening on the transport properties of a neutral graphene sheet is studied by directly probing its electronic structure. We find that the Fermi velocity, Dirac point velocity, and overall distortion of the Dirac cone are renormalized due to the screening of the electron-electron interaction in an unusual way. We also observe an increase of the electron mean free path due to the screening of charged impurities. These observations help us to understand the basis for the transport properties of graphene, as well as the fundamental physics of these interesting electron-electron interactions at the Dirac point crossing.