Hopfions are localized and topologically nontrivial magnetic configurations that have received considerable attention in recent years. In this Letter, we use a micromagnetic approach to analyze the scattering of spin waves (SWs) by magnetic hopfions. Our results evidence that SWs experience an electromagnetic field generated by the hopfion and sharing its topological properties. In addition, SWs propagating along the hopfion symmetry axis are deflected by the magnetic texture, which acts as a convergent or divergent lens, depending on the SWs’ propagation direction. Assuming that SWs propagate along the plane perpendicular to the symmetry axis, the scattering is closely related to the Aharonov-Bohm effect, allowing us to identify the magnetic hopfion as a scattering center.

The nonlinear polaronic response of electrons solvated in liquid 2-propanol is studied by two-dimensional terahertz spectroscopy. Solvated electrons with a concentration of $c_e\approx 800\mathrm{\mu }\mathrm{M}$ are generated by femtosecond photoionization of alcohol molecules. Electron relaxation to a localized ground state impulsively excites coherent polaron oscillations with a frequency of 3.9 THz. Off-resonant perturbation of the terahertz coherence by a pulse centered at 1.5 THz modifies the polaron oscillation phase. This nonlinear change of electron polarizability is reproduced by theoretical calculations.

Unraveling the oxidation of graphitic lattice is of great interest for atomic-scale lattice manipulation. Herein, we build epoxy cluster, atom by atom, using Van der Waals’ density-functional theory aided by Clar’s aromatic π-sextet rule. We predict the formation of cyclic epoxy trimers and its linear chains propagating along the armchair direction of the lattice to minimize the system’s energy. Using low-temperature scanning tunneling microscopy on oxidized graphitic lattice, we identify linear chains as bright features that have a threefold symmetry, and which exclusively run along the armchair direction of the lattice confirming the theoretical predictions.

The elastic Leidenfrost effect occurs when a vaporizable soft solid is lowered onto a hot surface. Evaporative flow couples to elastic deformation, giving spontaneous bouncing or steady-state floating. The effect embodies an unexplored interplay between thermodynamics, elasticity, and lubrication: despite being observed, its basic theoretical description remains a challenge. Here, we provide a theory of elastic Leidenfrost floating. As weight increases, a rigid solid sits closer to the hot surface. By contrast, we discover an elasticity-dominated regime where the heavier the solid, the higher it floats. This geometry-governed behavior is reminiscent of the dynamics of large liquid Leidenfrost drops. We show that this elastic regime is characterized by Hertzian behavior of the solid’s underbelly and derive how the float height scales with materials parameters. Introducing a dimensionless elastic Leidenfrost number, we capture the crossover between rigid and Hertzian behavior. Our results provide theoretical underpinning for recent experiments, and point to the design of novel soft machines.

We investigate the dynamics of soft sphere liquids through computer simulations for spatial dimensions from $d=3$ to 8, over a wide range of temperatures and densities. Employing a scaling of density-temperature-dependent relaxation times, we precisely identify the density ${\varphi }_0$, which marks the ideal glass transition in the hard sphere limit, and a crossover from sub- to super-Arrhenius temperature dependence. The difference between ${\varphi }_0$ and the athermal jamming density ${\varphi }_J$, small in 3 and 4 dimensions, increases with dimension, with ${\varphi }_0>{\varphi }_J$ for $d>4$. We compare our results with recent theoretical calculations.

The recent discovery of the striking sheetlike multicellular choanoflagellate species Choanoeca flexa that dynamically interconverts between two hemispherical forms of opposite orientation raises fundamental questions in cell and evolutionary biology, as choanoflagellates are the closest living relatives of animals. It similarly motivates questions in fluid and solid mechanics concerning the differential swimming speeds in the two states and the mechanism of curvature inversion triggered by changes in the geometry of microvilli emanating from each cell. Here we develop fluid dynamical and mechanical models to address these observations and show that they capture the main features of the swimming, feeding, and inversion of C. flexa colonies, which can be viewed as active, shape-shifting polymerized membranes.

For the efficient simulation of open quantum systems, we often use quantum jump trajectories given by pure states that evolve stochastically to unravel the dynamics of the underlying master equation. In the Markovian regime, when the dynamics is described by a Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) master equation, this procedure is known as Monte Carlo wave function approach. However, beyond ultraweak system-bath coupling, the dynamics of the system is not described by an equation of GKSL type, but rather by the Redfield equation, which can be brought into pseudo-Lindblad form. Here, negative dissipation strengths prohibit the conventional approach. To overcome this problem, we propose a pseudo-Lindblad quantum trajectory (PLQT) unraveling. It does not require an effective extension of the state space, like other approaches, except for the addition of a single classical bit. We test the PLQT for the eternal non-Markovian master equation for a single qubit and an interacting Fermi-Hubbard chain coupled to a thermal bath and discuss its computational effort compared to solving the full master equation.

In this Letter, we define the Aharony-Bergman-Jafferis-Maldacena loop momentum amplituhedron, which is a geometry encoding Aharony-Bergman-Jafferis-Maldacena planar tree-level amplitudes and loop integrands in the three-dimensional spinor helicity space. Translating it to the space of dual momenta produces a remarkably simple geometry given by configurations of spacelike separated off-shell momenta living inside a curvy polytope defined by momenta of scattered particles. We conjecture that the canonical differential form on this space gives amplitude integrands, and we provide a new formula for all one-loop $n$-particle integrands in the positive branch. For higher loop orders, we utilize the causal structure of configurations of points in Minkowski space to explain the singularity structure for known results at two loops.

Optical frequency metrology in atoms and ions can probe hypothetical fifth forces between electrons and neutrons by sensing minute perturbations of the electronic wave function induced by them. A generalized King plot has been proposed to distinguish them from possible standard model effects arising from, e.g., finite nuclear size and electronic correlations. Additional isotopes and transitions are required for this approach. Xenon is an excellent candidate, with seven stable isotopes with zero nuclear spin, however it has no known visible ground-state transitions for high resolution spectroscopy. To address this, we have found and measured twelve magnetic-dipole lines in its highly charged ions and theoretically studied their sensitivity to fifth forces as well as the suppression of spurious higher-order standard model effects. Moreover, we identified at 764.8753(16) nm a E2-type ground-state transition with 500 s excited state lifetime as a potential clock candidate further enhancing our proposed scheme.

The $x$ dependence of hadrons’ generalized parton distributions (GPDs) $\mathcal{F}(x,\xi ,t)$ is the most difficult to extract from the existing known processes, while the $\xi$ and $t$ dependence are uniquely determined by the kinematics of the scattered hadron. We study the single diffractive hard exclusive processes for extracting GPDs in the photoproduction. We demonstrate quantitatively the enhanced sensitivity on extracting the $x$ dependence of various GPDs from the photoproduction cross sections, as well as the asymmetries constructed from photon polarization and hadron spin that could be measured at JLab Hall D by GlueX Collaboration and future facilities.

We experimentally demonstrate stable trapping and controlled manipulation of silica microspheres in a structured optical beam consisting of a dark focus surrounded by light in all directions—the dark focus tweezer. Results from power spectrum and potential analysis demonstrate the nonharmonicity of the trapping potential landscape, which is reconstructed from experimental data in agreement to Lorentz-Mie numerical simulations. Applications of the dark tweezer in levitated optomechanics and biophysics are discussed.

We use the topological heavy fermion (THF) model and its Kondo lattice (KL) formulation to study the possibility of a symmetric Kondo (SK) state in twisted bilayer graphene. Via a large-$N$ approximation, we find a SK state in the KL model at fillings $\nu =0,\pm 1,\pm 2$ where a KL model can be constructed. In the SK state, all symmetries are preserved and the local moments are Kondo screened by the conduction electrons. At the mean-field level of the THF model at $\nu =0,\pm 1,\pm 2,\pm 3$ we also find a similar symmetric state that is adiabatically connected to the symmetric Kondo state. We study the stability of the symmetric state by comparing its energy with the ordered (symmetry-breaking) states found in [H. Hu et al., Phys. Rev. Lett. 131, 026502 (2023)., Z.-D. Song and B. A. Bernevig, Phys. Rev. Lett. 129, 047601 (2022).] and find the ordered states to have lower energy at $\nu =0,\pm 1,\pm 2$. However, moving away from integer fillings by doping the light bands, our mean-field calculations find the energy difference between the ordered state and the symmetric state to be reduced, which suggests the loss of ordering and a tendency toward Kondo screening. In order to include many-body effects beyond the mean-field approximation, we also performed dynamical mean-field theory calculations on the THF model in the nonordered phase. The spin susceptibility follows a Curie behavior at $\nu =0,\pm 1,\pm 2$ down to $\sim 2\mathrm{K}$ where the onset of screening of the local moment becomes visible. This hints to very low Kondo temperatures at these fillings, in agreement with the outcome of our mean-field calculations. At noninteger filling $\nu =\pm 0.5,\pm 0.8,\pm 1.2$ dynamical mean-field theory shows deviations from a $1/T$ susceptibility at much higher temperatures, suggesting a more effective screening of local moments with doping. Finally, we study the effect of a $C_{3z}$-rotational-symmetry-breaking strain via mean-field approaches and find that a symmetric phase (that only breaks $C_{3z}$ symmetry) can be stabilized at sufficiently large strain at $\nu =0,\pm 1,\pm 2$. Our results suggest that a symmetric Kondo phase is strongly suppressed at integer fillings, but could be stabilized either at noninteger fillings or by applying strain.

Recent experiments on weak polyelectrolyte brushes found marked shifts in the effective $\mathrm{p}{K}_a$ that are linear in the logarithm of the salt concentration. Comparing explicit-particle simulations with mean-field calculations we show that for high grafting densities the salt concentration effect can be explained using the ideal Donnan theory, but for low grafting densities the full shift is due to a combination of the Donnan effect and the polyelectrolyte effect. The latter originates from electrostatic correlations that are neglected in the Donnan picture and that are only approximately included in the mean-field theory. Moreover, we demonstrate that the magnitude of the polyelectrolyte effect is almost invariant with respect to salt concentration but depends on the grafting density of the brush. This invariance is due to a complex cancellation of multiple effects. Based on our results, we show how the experimentally determined $\mathrm{p}{K}_a$ shifts may be used to infer the grafting density of brushes, a parameter that is difficult to measure directly.

We report and characterize the emergence of a noise-induced state of quenched disorder in a generic model describing a dense sheet of active polar disks. In this state, self-propelled disks become jammed with random orientations, only displaying small fluctuations about their mean positions and headings. The quenched disorder phase appears at intermediate noise levels, between moving polar order and standard dynamic disorder. We show that it results from retrograde forces produced by angular fluctuations with Ornstein-Uhlenbeck dynamics, compute its critical noise, and argue that it could emerge in a variety of systems.

A key open question in the study of multiparticle production in high-energy $pp$ collisions is the relationship between the “ridge”—i.e., the observed azimuthal correlations between particles in the underlying event that extend over all rapidities—and hard or semihard scattering processes. In particular, it is not known whether jets or their soft fragments are correlated with particles in the underlying event. To address this question, two-particle correlations are measured in $pp$ collisions at $\sqrt{s}=13\mathrm{TeV}$ using data collected by the ATLAS experiment at the LHC, with an integrated luminosity of $15.8{\mathrm{pb}}^{-1}$, in two different configurations. In the first case, charged particles associated with jets are excluded from the correlation analysis, while in the second case, correlations are measured between particles within jets and charged particles from the underlying event. Second-order flow coefficients, $v_2$, are presented as a function of event multiplicity and transverse momentum. These measurements show that excluding particles associated with jets does not affect the measured correlations. Moreover, particles associated with jets do not exhibit any significant azimuthal correlations with the underlying event, ruling out hard processes contributing to the ridge.