We document experimentally four different interactions of a laser-induced bubble and a free-settling particle, with different combinations of the geometric and physical parameters of the system. Our force balance model shows that four nondimensional factors involving the particle radius $a$, the maximum bubble radius $R_{\max }$, the initial separation distance $l_0$ between the particle center and the bubble center, the fluid viscosity ${\mu }_f$, and the particle and fluid densities ${\rho }_p$ and ${\rho }_f$, respectively, in detail $l_0/R_{\max }$, $a/R_{\max }$, ${\rho }_p/{\rho }_f$, and ${\mu }^{*}={\mu }_f{T}_c/{\rho }_f{R}_{\max }^2$, where $T_c=0.915R_{\max }\sqrt{{\rho }_f/(p_{\infty }-p_v)}$, influence the particle-bubble dynamics, and reasonably predict the maximum particle velocity and the limiting condition when the particle starts to “bounce off” the bubble during bubble growth. In particular, we also discover the high-speed ejection of the particle, and a cavity behind the particle, in cases when initially the particle is in very close proximity to the bubble. These observations offer new insights into the causal mechanism for the enhanced cavitation erosion in silt-laden water.

We present measurements of the spectrally resolved x rays emitted from solid-density magnesium targets of varying sub-$\mu \mathrm{m}$ thicknesses isochorically heated by an x-ray laser. The data exhibit a largely thickness-independent source function, allowing the extraction of a measure of the opacity to $K$-shell x rays within well-defined regimes of electron density and temperature, extremely close to local thermodynamic equilibrium conditions. The deduced opacities at the peak of the $K\alpha$ transitions of the ions are consistent with those predicted by detailed atomic-kinetics calculations.

Field-line localized ballooning modes have been observed at the edge of high confinement mode plasmas in ASDEX Upgrade with rotating 3D perturbations induced by an externally applied $n=2$ error field and during a moderate level of edge localized mode mitigation. The observed ballooning modes are localized to the field lines which experience one of the two zero crossings of the radial flux surface displacement during one rotation period. The localization of the ballooning modes agrees very well with the localization of the largest growth rates from infinite-$n$ ideal ballooning stability calculations using a realistic 3D ideal magnetohydrodynamic equilibrium. This analysis predicts a lower stability with respect to the axisymmetric case. The primary mechanism for the local lower stability is the 3D distortion of the local magnetic shear.

The competition between the length scales associated with the periodicity of a lattice potential and the cyclotron radius of a uniform magnetic field is known to have dramatic effects on the single-particle properties of a quantum particle, e.g., the fractal spectrum is known as the Hofstadter butterfly. Having this intricate competition in mind, we consider a two-component Fermi gas on a square optical lattice with opposite synthetic magnetic fields for the components, and study its effects on the many-body BCS-pairing phenomenon. By a careful addressing of the distinct superfluid transitions from the semimetal, quantum spin-Hall insulator, or normal phases, we explore the low-temperature phase diagrams of the model, displaying lobe structures that are reminiscent of the well-known Mott-insulator transitions of the Bose-Hubbard model.

Bismuth telluride (${\mathrm{Bi}}_2{\mathrm{Te}}_3$) based thermoelectric (TE) materials have been commercialized successfully as solid-state power generators, but their low mechanical strength suggests that these materials may not be reliable for long-term use in TE devices. Here we use density functional theory to show that the ideal shear strength of ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ can be significantly enhanced up to 215% by imposing nanoscale twins. We reveal that the origin of the low strength in single crystalline ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ is the weak van der Waals interaction between the Te1 coupling two $\mathrm{Te}1─\mathrm{Bi}─\mathrm{Te}2─\mathrm{Bi}─\mathrm{Te}1$ five-layer quint substructures. However, we demonstrate here a surprising result that forming twin boundaries between the Te1 atoms of adjacent quints greatly strengthens the interaction between them, leading to a tripling of the ideal shear strength in nanotwinned ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ (0.6 GPa) compared to that in the single crystalline material (0.19 GPa). This grain boundary engineering strategy opens a new pathway for designing robust ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ TE semiconductors for high-performance TE devices.

We study the mechanical behavior of three-dimensional, randomly microcracked continua for crack densities up to and above the transport percolation threshold. We show the existence of a fully fragmented material state in which stiffness is preserved due to topological interlocking of fragments. In this regime, the mechanical behavior is controlled by the contacts between fragments and becomes nonlinear. The upper limit of crack densities for which this behavior is observed, the stiffness percolation threshold, is identified. The variation of the effective material stiffness for crack densities ranging from 0 to the stiffness percolation threshold is reported.

We show that the anisotropy of the effective spin model for the dimer Mott insulator phase of $\kappa$-$(\mathrm{BEDT}\text{−}\mathrm{TTF}{)}_{2}X$ salts is dramatically different from that of the underlying tight-binding model. Intradimer quantum interference results in a model of coupled spin chains, where frustrated interchain interactions suppress long-range magnetic order. Thus, we argue, the “spin liquid” phase observed in some of these materials is a remnant of the Tomonaga-Luttinger physics of a single chain. This is consistent with previous experiments and resolves some outstanding puzzles.

Optoelectronic excitations in monolayer ${\mathrm{MoS}}_2$ manifest from a hierarchy of electrically tunable, Coulombic free-carrier and excitonic many-body phenomena. Investigating the fundamental interactions underpinning these phenomena—critical to both many-body physics exploration and device applications—presents challenges, however, due to a complex balance of competing optoelectronic effects and interdependent properties. Here, optical detection of bound- and free-carrier photoexcitations is used to directly quantify carrier-induced changes of the quasiparticle band gap and exciton binding energies. The results explicitly disentangle the competing effects and highlight longstanding theoretical predictions of large carrier-induced band gap and exciton renormalization in two-dimensional semiconductors.

The diffusion of molecules in complex systems such as glasses and cell cytoplasm is slow, heterogeneous, and sometimes nonergodic. The effects of such intriguing diffusion on the kinetics of chemical and biological reactions remain elusive. In this Letter, we report that the kinetics of the polymer loop formation reaction in a Kob-Andersen (KA) glass forming liquid is influenced significantly by the dynamic heterogeneity. The diffusion coefficient $D$ of a KA liquid deviates from the Stokes-Einstein relation at low temperatures and $D$ shows a fractional dependence on the solvent viscosity ${\eta }_s$, i.e., $D\sim {\eta }_s^{-{\xi }_D}$ with ${\xi }_D=0.85$. The dynamic heterogeneity of a KA liquid affects the rate constant $k_{\mathrm{rxn}}$ of the loop formation and leads to the identical fractional dependence of $k_{\mathrm{rxn}}$ on ${\eta }_s$ with $k_{\mathrm{rxn}}\sim {\eta }_s^{-\xi }$ and $\xi ={\xi }_D$, contrary to reactions in dynamically homogeneous solutions where $k_{\mathrm{rxn}}\sim {\eta }_s^{-1}$.

Quantum Fourier transforms (QFTs) have gained increased attention with the rise of quantum walks, boson sampling, and quantum metrology. Here, we present and demonstrate a general technique that simplifies the construction of QFT interferometers using both path and polarization modes. On that basis, we first observe the generalized Hong-Ou-Mandel effect with up to four photons. Furthermore, we directly exploit number-path entanglement generated in these QFT interferometers and demonstrate optical phase supersensitivities deterministically.

One of the most striking features of quantum theory is the existence of entangled states, responsible for Einstein’s so called “spooky action at a distance.” These states emerge from the mathematical formalism of quantum theory, but to date we do not have a clear idea of the physical principles that give rise to entanglement. Why does nature have entangled states? Would any theory superseding classical theory have entangled states, or is quantum theory special? One important feature of quantum theory is that it has a classical limit, recovering classical theory through the process of decoherence. We show that any theory with a classical limit must contain entangled states, thus establishing entanglement as an inevitable feature of any theory superseding classical theory.

We propose to search for light $U(1)$ dark photons, $A^{\prime }$, produced via kinetically mixing with ordinary photons via the Compton-like process, $\gamma e^{-}\to A^{\prime }{e}^{-}$, in a nuclear reactor and detected by their interactions with the material in the active volumes of reactor neutrino experiments. We derive 95% confidence-level upper limits on $\epsilon$, the $A^{\prime }-\gamma$ mixing parameter, $\epsilon$, for dark-photon masses below 1 MeV of $\epsilon <1.3\times {10}^{-5}$ and $\epsilon <2.1\times {10}^{-5}$, from NEOS and TEXONO experimental data, respectively. This study demonstrates the applicability of nuclear reactors as potential sources of intense fluxes of low-mass dark photons.

The exotic nucleus ${}^{11}\mathrm{Be}$ has been extensively studied and much experimental information is available on the structure of this system. We treat, within the framework of renormalized nuclear field theory in both configuration and 3D space, the mixing of bound and continuum single-particle states through the coupling to collective vibrations of the ${}^{10}\mathrm{Be}$ core. We also take care of the Pauli principle acting not only between the single valence particle explicitly considered and those participating in the collective states, but also between fermions involved in two-phonon virtual states dressing the single-particle motion. In this way, it is possible to simultaneously and quantitatively account for the energies of the $1/2^{+}$, $1/2^{-}$ low-lying states, the centroid and line shape of the $5/2^{+}$ resonance and the one-nucleon stripping and pickup absolute differential cross sections involving ${}^{11}\mathrm{Be}$ as either target or residual nucleus. Also for the dipole transition connecting the $1/2^{+}$ and $1/2^{-}$ parity inverted levels as well as the isotopic shift of the charge radius. Theory provides a unified and exhaustive nuclear structure and reaction characterization of the many-body effects which are at the basis of this paradigmatic one-neutron halo system.

We have measured fully differential cross sections for electron capture in 75 keV $p+{\mathrm{H}}_2$ collisions with subsequent dissociation of the intermediate molecular ${\mathrm{H}}_2^{+}$ ion by vibrational excitation using different projectile coherence lengths. Data were obtained for two molecular orientations as a function of projectile scattering angle. Two types of interference, single- and molecular two-center interference, were identified. The two-center interference structure is phase shifted by $\pi$ compared to what we expected. Furthermore, the presence of projectile coherence effects could be reconfirmed.

Cluster synchronization is a phenomenon in which a network self-organizes into a pattern of synchronized sets. It has been shown that diverse patterns of stable cluster synchronization can be captured by symmetries of the network. Here, we establish a theoretical basis to divide an arbitrary pattern of symmetry clusters into independently synchronizable cluster sets, in which the synchronization stability of the individual clusters in each set is decoupled from that in all the other sets. Using this framework, we suggest a new approach to find permanently stable chimera states by capturing two or more symmetry clusters—at least one stable and one unstable—that compose the entire fully symmetric network.

In strained heteroepitaxy, two-dimensional layers can exhibit a critical thickness at which three-dimensional islands self-assemble, relieving misfit strain at the cost of an increased surface area. Here we show that such a morphological phase transition can be induced on demand using surfactants. We explore Bi as a surfactant in the growth of InAs on GaAs(110), and find that the presence of surface Bi induces Stranski-Krastanov growth of 3D islands, while growth without Bi always favors 2D layer formation. Exposing a static two monolayer thick InAs layer to Bi rapidly transforms the layer into 3D islands. Density functional theory calculations reveal that Bi as well as Sb reduce the energetic cost of 3D island formation by modifying surface energies. These 3D nanostructures behave as optically active quantum dots. This work illustrates how surfactants can enable quantum dot self-assembly where it otherwise would not occur.

We employ a recently developed computational many-body technique to study for the first time the half-filled Anderson-Hubbard model at finite temperature and arbitrary correlation $U$ and disorder $V$ strengths. Interestingly, the narrow zero temperature metallic range induced by disorder from the Mott insulator expands with increasing temperature in a manner resembling a quantum critical point. Our study of the resistivity temperature scaling $T^{\alpha }$ for this metal reveals non-Fermi liquid characteristics. Moreover, a continuous dependence of $\alpha$ on $U$ and $V$ from linear to nearly quadratic is observed. We argue that these exotic results arise from a systematic change with $U$ and $V$ of the “effective” disorder, a combination of quenched disorder and intrinsic localized spins.

We elucidate the origin of the phonon-mediated superconductivity in $2H$-${\mathrm{NbS}}_2$ using the ab initio anisotropic Migdal-Eliashberg theory including Coulomb interactions. We demonstrate that superconductivity is associated with Fermi surface hot spots exhibiting an unusually strong electron-phonon interaction. The electron-lattice coupling is dominated by low-energy anharmonic phonons, which place the system on the verge of a charge density wave instability. We also provide definitive evidence for two-gap superconductivity in $2H$-${\mathrm{NbS}}_2$, and show that the low- and high-energy peaks observed in tunneling spectra correspond to the $\mathrm{\Gamma }$- and $K$-centered Fermi surface pockets, respectively. The present findings call for further efforts to determine whether our proposed mechanism underpins superconductivity in the whole family of metallic transition metal dichalcogenides.

We theoretically study the interplay between bulk Weyl electrons and magnetic topological defects, including magnetic domains, domain walls, and ${\mathbb{Z}}_6$ vortex lines, in the antiferromagnetic Weyl semimetals ${\mathrm{Mn}}_3\mathrm{Sn}$ and ${\mathrm{Mn}}_3\mathrm{Ge}$ with negative vector chirality. We argue that these materials possess a hierarchy of energy scales, which allows a description of the spin structure and spin dynamics using an $XY$ model with ${\mathbb{Z}}_6$ anisotropy. We propose a dynamical equation of motion for the $XY$ order parameter, which implies the presence of ${\mathbb{Z}}_6$ vortex lines, the double-domain pattern in the presence of magnetic fields, and the ability to control domains with current. We also introduce a minimal electronic model that allows efficient calculation of the electronic structure in the antiferromagnetic configuration, unveiling Fermi arcs at domain walls, and sharp quasibound states at ${\mathbb{Z}}_6$ vortices. Moreover, we have shown how these materials may allow electronic-based imaging of antiferromagnetic microstructure, and propose a possible device based on the domain-dependent anomalous Hall effect.