Manipulating elastic waves in lower-dimensional mechanical metamaterials has attracted much attention since it lays the foundation for the design of various elastic functional devices, especially for on-chip size. However, due to the experimental challenges, it is very difficult to control elastic waves in higher dimensions. In this Letter, we introduce an extra structural parameter to synthesize and investigate the on-chip Weyl physics in silicon-on-insulator system. Interestingly, we engineer an in-plane pseudomagnetic field to realize chiral Landau levels, which provides a bulk channel supporting robust energy transport. We also observe the pseudomagnetic field-induced boundary states near the diagonal corners, which are quite different from conventional higher order topological corner states. With the aid of the synthetic dimension, we can not only realize the multidimensional elastic wave manipulations, but more importantly, devise a novel strategy to explore the higher dimensional physics on an integrated platform.

The chiral lattice structure of twisted bilayer graphene with $D_6$ symmetry allows for intrinsic photogalvanic effects only at off-normal incidence, while additional extrinsic effects are known to be induced by a substrate or a gate potential. In this Letter, we first compute the intrinsic effects and show they reverse sign at the magic angle, revealing a band inversion at the $\mathrm{\Gamma }$ point. We next consider different extrinsic effects, showing how they can be used to track the strengths of the substrate coupling or electric displacement field. We also show that the approximate particle-hole symmetry implies stringent constraints on the chemical potential dependence of all photocurrents. A detailed comparison of intrinsic vs extrinsic photocurrents therefore reveals a wealth of information about the band structure and can also serve as a benchmark to constrain the symmetry breaking patterns of correlated states.

The spin pumping effect in antiferromagnets, which ultimately converts THz waves into a spin current, is the key physical mechanism leading to an essential function which harnesses the THz technology and spintronics. Here, we report thorough experimental investigations of the spin current induced by the antiferromagnetic spin pumping effect in epitaxial $\alpha \text{−}{\mathrm{Fe}}_2{\mathrm{O}}_3$ thin films having two distinct dynamic modes and unambiguously show that both the inter- and intrasublattice spin mixing conductance are equally substantial. Our experimental insight is an important advance for understanding the physics of transduction between the spin current and the staggered magnetization dynamics at THz frequency.

The role of self-intercalation in 2D van der Waals materials is key to the understanding of many of their properties. Here we show that the magnetic ordering temperature of thin films of the 2D ferromagnet ${\mathrm{Fe}}_5{\mathrm{GeTe}}_2$ is substantially increased by self-intercalated Fe that resides in the van der Waals gaps. The epitaxial films were prepared by molecular beam epitaxy and their magnetic properties explored by element-specific x-ray magnetic circular dichroism that showed ferromagnetic ordering up to 375 K. Both surface and bulk sensitive x-ray absorption modes were used to confirm that the magnetic signal is of an intrinsic nature. Fe occupation within the van der Waals gap was determined by x-ray diffraction which showed a notably higher occupation with respect to bulk crystals. We thus infer, supported by first-principles calculations, that the higher magnetic ordering temperature results from an increased exchange interaction between the individual ${\mathrm{Fe}}_5{\mathrm{GeTe}}_2$ layers mediated by Fe atoms residing within the van der Waals gaps. Our findings establish self-intercalation during epitaxial growth as an efficient mechanism to achieve high-temperature magnetism in a broad class of van der Waals materials.

We show that spontaneous density segregation in dense systems of aligning circle swimmers is a condensation phenomenon at odds with the phase separation scenarios usually observed in two-dimensional active matter. The condensates, which take the form of vortices or rotating polar packets, can absorb a finite fraction of the particles in the system, and keep a finite or slowly growing size as their mass increases. Our results are obtained both at particle and continuous levels. We consider both ferromagnetic and nematic alignment, and both identical and disordered chiralities. Condensation implies synchronization, even though our systems are in 2D and bear strictly local interactions. We propose a phenomenological theory based on observed mechanisms that accounts qualitatively for our results.

Work extraction is one of the most central processes in quantum thermodynamics. However, the prior analysis of optimal extractable work has been restricted to a limited operational scenario where complete information about the initial state is given. Here, we introduce a general framework of black box work extraction, which addresses the inaccessibility of information on the initial state. We show that the optimal extractable work in the black box setting is completely characterized by the performance of a composite hypothesis testing task, a fundamental problem in information theory. We employ this general relation to reduce the asymptotic black box work extraction to the quantum Stein’s lemma in composite hypothesis testing, allowing us to provide their exact characterization in terms of the Helmholtz free energy. We also show a new quantum Stein’s lemma motivated in this physical setting, where a composite hypothesis contains a certain correlation. Our Letter exhibits the importance of information about the initial state and gives a new interpretation of the quantities in the composite quantum hypothesis testing, encouraging the interplay between the physical settings and the information theory.

A search for violation of the charge-parity ($CP$) symmetry in the $D^{+}\to K^{-}{K}^{+}{\pi }^{+}$ decay is presented, with proton-proton collision data corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$, collected at a center-of-mass energy of 13 TeV with the LHCb detector. A novel model-independent technique is used to compare the $D^{+}$ and $D^{-}$ phase-space distributions, with instrumental asymmetries subtracted using the $D_s^{+}\to K^{-}{K}^{+}{\pi }^{+}$ decay as a control channel. The $p$ value for the hypothesis of $CP$ conservation is 8.1%. The $CP$ asymmetry observables $A_{CP|S}^{\varphi {\pi }^{+}}=(0.95\pm 0.43_{\mathrm{stat}}\pm 0.26_{\mathrm{syst}})\times {10}^{-3}$ and $A_{CP|S}^{{\overline{K}}^{*0}{K}^{+}}=(-0.26\pm 0.56_{\mathrm{stat}}\pm 0.18_{\mathrm{syst}})\times {10}^{-3}$ are also measured. These results show no evidence of $CP$ violation and represent the most sensitive search performed through the phase space of a multibody decay.

High-energy nuclear collisions create a quark-gluon plasma, whose initial condition and subsequent expansion vary from event to event, impacting the distribution of the eventwise average transverse momentum [$P([p_{\mathrm{T}}])$]. Disentangling the contributions from fluctuations in the nuclear overlap size (geometrical component) and other sources at a fixed size (intrinsic component) remains a challenge. This problem is addressed by measuring the mean, variance, and skewness of $P([p_{\mathrm{T}}])$ in ${}^{208}\mathrm{Pb}+{}^{208}\mathrm{Pb}$ and ${}^{129}\mathrm{Xe}+{}^{129}\mathrm{Xe}$ collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ and 5.44 TeV, respectively, using the ATLAS detector at the LHC. All observables show distinct features in ultracentral collisions, which are explained by a suppression of the geometrical component as the overlap area reaches its maximum. These results demonstrate a new technique to separate geometrical and intrinsic fluctuations, providing constraints on initial conditions and properties of the quark-gluon plasma, such as the speed of sound.

We have observed the laser-assisted dynamic interference in the electron spectra triggered by attosecond pulse trains. The fingerprints of finer interference fringes, much smaller than the laser photon energy, have been clearly identified experimentally. Our measurements are successfully reproduced by theoretical simulations utilizing the numerical solution to the time-dependent Schrödinger equation and the strong-field approximation. Further explorations based on the saddle point analysis and a simple quantum model strengthen our finding and reveal the importance of the phase variations of the electron wave packets, which are modulated by the vector potential across the envelope of the strong laser pulse. Our studies show that the dynamic interference can be captured and the electron in the continuum can be effectively manipulated by the current attosecond-controlled multicolor laser approach.

We investigate the experimental control of pair tunneling in a double-well potential using Floquet engineering. We demonstrate a crossover from a regime with density-assisted tunneling to dominant pair tunneling by tuning the effective interactions. Furthermore, we show that the pair tunneling rate can be enhanced not only compared to the Floquet-reduced single-particle tunneling but even beyond the static superexchange rate, while keeping the effective interaction in a relevant range. This opens possibilities to realize models with explicit pair tunneling in ultracold atomic systems.

High-dimensional multipartite entanglement plays a crucial role in quantum information science. However, existing schemes for generating such entanglement become complex and costly as the dimension of quantum units increases. In this Letter, we overcome the limitation by proposing a significantly enhanced linear optical heralded scheme that generates the $d$-level $N$-partite Greenberger-Horne-Zeilinger (GHZ) state with single-photon sources and linear operations. Our scheme requires $dN$ photons, which is the minimal required photon number, with substantially improved success probability from previous schemes. It employs linear optical logic gates compatible with any qudit encoding system and can generate generalized GHZ states with installments of beam splitters. With efficient generations of high-dimensional resource states, our work opens avenues for further exploration in high-dimensional quantum information processing.

Electric quadrupole traps are a leading technology for suspending charged objects ranging in size from single protons to atomic and molecular ions, and even to nano- and micron-sized bodies. If the levitated objects’ charge distribution contains multipoles, the time-dependent trapping fields can significantly impact its rotational motion. Here, we experimentally observe the transition from librational motion to a regime where a microparticle rotates in sync with the trap drive. We theoretically explain that the locked motion is caused by the torques acting on the electric quadrupole, which can thus be expected to be ubiquitous for nonspherical micro-objects. We demonstrate the versatility of this method by spinning diverse particles such as silicon microrods, magnetic particles, and microdiamonds. For diamonds, we show that the rotational motion can be precisely characterized by stroboscopic readout of the embedded nitrogen vacancy centers. Given its generality, we anticipate that this technique will become an important tool for future experiments in levitated quantum nanomechanics.

When a two-component mixture of immiscible fluids is stirred, the fluids are split into smaller domains with more vigorous stirring. We numerically investigate the sizes of such domains in a fully developed turbulent state of a two-component superfluid stirred with energy input rate $\epsilon$. For the strongly immiscible condition, the typical domain size is shown to be proportional to ${\epsilon }^{-2/5}$, as predicted by the Kolmogorov-Hinze theory in classical fluids. For the weakly immiscible condition, quantum effects become pronounced and the power changes from $-2/5$ to $-1/4$.

Pump-probe response of the spin-orbit coupled Mott insulator ${\mathrm{Sr}}_2{\mathrm{IrO}}_4$ reveals a rapid creation of low-energy optical weight and suppression of three-dimensional magnetic order on laser pumping. Postpump there is a quick reduction of the optical weight but a very slow recovery of the magnetic order—the difference is attributed to weak interlayer exchange in ${\mathrm{Sr}}_2{\mathrm{IrO}}_4$ delaying the recovery of three-dimensional magnetic order. We suggest that the effect has a very different and more fundamental origin. Combining spatiotemporal mean field dynamics and Langevin dynamics on the photoexcited Mott-Hubbard insulator, we show that the timescale difference is not a dimensional effect but is intrinsic to charge dynamics versus order reconstruction in a correlated system. In two dimensions, we obtain a short, almost pump-fluence-independent timescale for charge dynamics, while recovery time of magnetic order involves domain growth and increases rapidly with fluence. Apart from addressing the iridate Mott problem, our approach can be used to analyze phase competition and spatial ordering in superconductors and charge ordered systems out of equilibrium.

We investigate the scaling behavior of Nambu-Goldstone modes in the ordered phase of the Vicsek model, introducing a phenomenological equation of motion incorporating a previously overlooked nonlinear term. This term arises from the interaction between velocity fields and density fluctuations, leading to new scaling behaviors. We derive exact scaling exponents in two dimensions, which reproduce the isotropic scaling behavior reported in a prior numerical simulation.

The dimension of a quantum state is traditionally seen as the number of superposed distinguishable states in a given basis. We propose an absolute, i.e., basis-independent, notion of dimensionality for ensembles of quantum states. It is based on whether a quantum ensemble can be simulated with states confined to arbitrary lower-dimensional subspaces and classical postprocessing. In order to determine the absolute dimension of quantum ensembles, we develop both analytical witness criteria and a semidefinite programming criterion based on the ensemble’s information capacity. Furthermore, we construct explicit simulation models for arbitrary ensembles of pure quantum states subject to white noise, and in natural cases we prove their optimality. Also, efficient numerical methods are provided for simulating generic ensembles. Finally, we discuss the role of absolute dimensionality in high-dimensional quantum information processing.

The BESIII Collaboration recently performed a precise measurement of the $e^{+}{e}^{-}\to D\overline{D}$ Born cross sections, and confirmed the $G(3900)$ structure reported by BABAR and Belle with high significance. We identify the $G(3900)$ as the first $P$-wave $D{\overline{D}}^{*}/\overline{D}{D}^{*}$ molecular resonance. The experimental and theoretical identification of the $P$-wave dimeson state holds paramount importance in enhancing our comprehension of the nonperturbative QCD and few-body physics. Its existence is firmly established in a unified meson-exchange model that simultaneously depicts the features of the ${\chi }_{c1}(3872)$, $Z_c(3900)$, and $T_{cc}(3875)$. This scenario can be directly examined in the $e^{+}{e}^{-}\to D{\overline{D}}^{*}/\overline{D}{D}^{*}$ cross section by seeing whether a resonance exists at the threshold. The credibility of the investigations is also ensured by the fact that the $P$-wave interaction dominantly arises from the well-known long-range pion exchange. Additionally, thanks to the centrifugal barrier, it is easier to form resonances in $P$-wave than in $S$-wave. We extensively calculate all systems up to $P$-wave with various quantum numbers and predict a dense population of the $D{\overline{D}}^{*}/\overline{D}{D}^{*}$ and $D{D}^{*}$ states, where the $S$-wave $D{\overline{D}}^{*}/\overline{D}{D}^{*}$ state with $I^G(J^{PC})=0^{-}(1^{+-})$, $P$-wave $D{\overline{D}}^{*}/\overline{D}{D}^{*}$ state with $I^G(J^{PC})=0^{+}(0^{-+})$, and $P$-wave $D{D}^{*}$ state with $I(J^P)=0(0^{-})$ are more likely to be observed in experiments.

The transverse-momentum-dependent distributions (TMDs), which are defined by gauge-invariant 3D parton correlators with staple-shaped lightlike Wilson lines, can be calculated from quark and gluon correlators fixed in the Coulomb gauge on a Euclidean lattice. These quantities can be expressed gauge invariantly as the correlators of Coulomb-gauge-dressed fields, which reduce to the standard TMD correlators under principal-value prescription in the infinite boost limit. In the framework of large-momentum effective theory, a quasi-TMD defined from such correlators in a large-momentum hadron state can be matched to the TMD via a factorization formula, whose exact form is derived using soft collinear effective theory and verified at one-loop order. Compared to the currently used gauge-invariant correlators, this new method can substantially improve statistical precision and simplify renormalization for the time-reversal-even TMDs, which will greatly enhance the predicative power of lattice QCD in the nonperturbative region.