We present the first results of a comprehensive microscopic approach to describe nucleus-nucleus elastic collisions by means of an optical potential derived at first order in multiple-scattering theory and computed by folding the projectile and target nuclear densities with the nucleon-nucleon $t$ matrix, which describes the interaction between each nucleon of the projectile and each nucleon of the target. Chiral interactions are consistently used in the calculation of the $t$ matrix and of the nonlocal nuclear densities, which are computed within the ab initio no-core shell model. Cross sections calculated for $\alpha$ collisions on ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$ at projectile energies in the range 100–300 MeV are presented and compared with available data. For momentum transfer $q$ up to about $1.0{\mathrm{fm}}^{-1}$ our results are in good agreement with the experimental data, whereas for higher momenta a reduction of the imaginary contributions is needed.

We propose and demonstrate that peripheral neutron-$\alpha$ scattering at low energies can serve as a sensitive and clean probe of the long-range three-nucleon forces. To this aim, we perform ab initio quantum Monte Carlo calculations using two- and three-nucleon interactions derived in chiral effective field theory up to third expansion order. We show that the longest-range three-nucleon force stemming from the two-pion exchange plays a crucial role in the proper description of the neutron-$\alpha$ $D$-wave phase shifts. Our Letter reveals the predictive power of chiral symmetry in the few-body sector and opens a new direction for probing and constraining three-nucleon forces.

We propose a scheme to generate solitons in arbitrary dimensions, in a matter-wave interferometer, without the need of quantum degeneracy. In our setting, solitons emerge by balancing the single-particle dispersion with engineered cavity-mediated exchange interactions between two wave packets, which, at the appropriate conditions, remain bound to each other and dispersion-free. For detection in thermal gases, we propose an interferometric probing scheme instead of traditional time-of-flight imaging.

The transport of light in disordered media is governed by open transmission channels, which enable nearly complete transmission of the incident power, despite low average transmission. Extensively studied in diffusive media and chaotic cavities, open channels exhibit unique properties such as universal spatial structure and extended dwell times. However, their experimental study is challenging due to the large number of modes required for control and measurement. We propose a multimode fiber cavity (MMFC) as a platform to explore open channels. Leveraging mode confinement and finite angular spread, MMFCs enabled full channel control, yielding an 18-fold power enhancement in experiment by selectively exciting an open channel with a transmission of $0.90\pm 0.04$. By analyzing 100 transmission matrices of MMFC realizations, we observed a bimodal transmission eigenvalue distribution, indicating high channel control and low losses. The scalability of MMFCs, combined with long dwell times and potential for nonlinear phenomena, offers new opportunities for studying complex wave transport.

One of the most fundamental questions in laser physics is the following: Which mode of an optical cavity will reach the lasing threshold first when gain is applied? Intuitively, the answer appears straightforward: When a particular mode is both temporally well confined (i.e., exhibits the highest quality factor) and experiences initially the largest increase of the modal gain, it is naturally expected to lase first. However, in this Letter, we demonstrate that this intuition can fail in surprising ways. Specifically, we show that in the presence of non-Hermitian degeneracies, known as exceptional points, the expected mode hierarchy can be dramatically altered. These spectral singularities can give rise to counterintuitive mode switching, where a mode with a lower quality factor and initially smaller increase of modal gain reaches the lasing threshold ahead of a more favorable competitor. Remarkably, this effect can occur even under spatially uniform pumping, underscoring the subtle and profound influence of non-Hermitian physics on lasing dynamics.

Experiments in the Wendelstein 7-X (W7-X) stellarator with plasma density beyond the established density limit in stellarators [Scalings of energy confinement and density limit in stellarator/heliotron devices, Nucl. Fusion 30, 11 (1990).] resulted in unusual, reduced size, fully radiative plasmas lasting stably for many confinement times [Small, stable plasmas, fully decoupled from the plasma-facing components in W7-X, Stellarator News 175, 1 (2021).]. In these experiments, the plasma had shrunk to a significantly smaller minor radius due to intense edge radiation from a radiating mantle and had no contact with material components, yet it remained relatively well confined for many confinement times with electron temperatures on the order of 1 keV. To our knowledge, this is the first definitive experimental long-time stability demonstration of such high-temperature contactless plasmas in the laboratory. It is shown that the onset and extent of this fully radiative small plasma state is predictable. The stability of the plasma size is elucidated with a simple power-balance model. In other helical devices such as the Large Helical Device (LHD) and the Wendelstein 7-AS (W7-AS), plasmas that start shrinking suffered from core impurity accumulation leading to a collapse whereas this was generally not observed for these W7-X plasmas.

The search for a giant Nernst effect beyond conventional mechanisms offers advantages for developing advanced thermoelectric devices and understanding charge-entropy conversion. Here, we study the Seebeck and Nernst effects in ${\mathrm{HfTe}}_5$ across a broad range of magnetic fields. Remarkably, the Nernst effect forms a giant plateau at ultrahigh magnetic fields ($B>10B_{QL}$), with the magnitude reaching up to $50\mathrm{\mu }\mathrm{V}/\mathrm{K}$ at 2 K. By tracking two magnetic-field-driven phase transitions predicted for weak topological insulators, we find that the giant Nernst plateau exists exclusively in the ideal 1D Weyl phase. Theoretical analysis further demonstrates that such a giant Nernst plateau arises from the unique thermoelectric conversion mechanism inherent to the ideal 1D Weyl phase, where the transverse thermoelectric effect (Nernst effect) is dominated by the longitudinal conduction channel. Our findings expand the understanding of ideal Weyl physics and open new avenues for significantly improving thermoelectric conversion efficiency.

Pseudomagnetic fields (PMFs) have been proven useful for generating Landau levels and controlling wave propagation in classical wave systems. Recently, photonic flat Landau levels residing near the $K$ and $K^{\prime }$ points induced by PMFs have been realized through uniaxial gradient deformations of superlattices. Here, we report the realization of flat Landau levels near the $\mathrm{\Gamma }$ point in Dirac photonic crystals with wider-range uniaxial gradient deformations, induced by antisymmetric, nonuniform PMFs. The flat Landau levels appear as spatially localized, doubly degenerate bulk modes, and are associated with dispersive valley kink modes. The nonuniform PMF distributions provide an additional degree of freedom that can enhance the flatness of flat Landau levels that extends for an expanded $k$-space range. We experimentally visualized the band dispersion of flat Landau levels and observed both localized flat Landau level modes and chiral valley kink modes. Our results pave a new avenue for manipulating electromagnetic wave localization and transport via PMFs.

Based upon first-principles calculations, we report ultralow Gilbert damping in two-dimensional (2D) van der Waals ferromagnets. The low damping occurs at weak scattering because mirror symmetry prohibits intraband transitions. The monotonic dependence on the electronic scattering rate suggests the absent lower limit, in contrast to conventional ferromagnetic materials. Breaking mirror symmetry through magnetization rotation, layer stacking, or structural phase transition significantly increases damping by enabling intraband transitions. Topological nodal lines, also protected by mirror symmetry, contribute substantially to interband-transition-mediated damping, which can be tuned by adjusting the Fermi level. Our findings elucidate the unique characteristics of Gilbert damping in 2D van der Waals ferromagnets, providing valuable insights for designing low-dimensional spintronic devices with high energy efficiency.

Altermagnetism is a newly discovered magnetic phase, characterized by nonrelativistic spin splitting that has been experimentally observed. Here, we introduce a framework dubbed “spin-orbital altermagnetism” to achieve spin-orbital textures in altermagnetic materials. We identify two distinct classes of spin-orbital altermagnetism: intrinsic and extrinsic. The intrinsic type emerges from symmetry-compensated magnetic orders with spontaneously broken parity-time symmetry, while the extrinsic type stems from translational symmetry breaking between sublattices, as exemplified by the Jahn-Teller-driven structural phase transition. In addition to directly measuring the spin-orbital texture, we propose spin conductivity and spin-resolved orbital polarization as effective methods for detecting these altermagnets. Additionally, a symmetry-breaking mechanism induces weak spin magnetization, further revealing the peculiar feature of spin-orbital altermagnetism. We also utilize the staggered susceptibility to illustrate a potential realization of this phase in a two-orbital interacting system. Our Letter provides a new platform to explore spin-orbital locked physics, extending the materials classes that may display complex spin textures from the standard $4d-5d$ compounds to $3d$ compounds.

Ensuring a smooth rate of efflux of particles from an outlet without unpredictable clogging events is crucial in processing powders and grains. We show by experiments and simulations that an obstacle placed near the outlet can greatly suppress clog formation in a 3-dimensional granular flow; this counterintuitive phenomenon had previously been demonstrated in 2-dimensional systems. Remarkably, clog suppression is very effective even when the obstacle cross section is comparable to that of a single grain and is only a small fraction of the outlet area. Data from two dissimilar obstacle shapes indicate that the underlying mechanism for clog suppression is geometric: while the magnitude of the effect can be affected by dynamical factors, the optimal location of the obstacle is not and follows a simple geometric rule. An optimally placed obstacle arranges for the most probable clogging arch to be at a perilous and unstable spot, where the flow geometry is at a point of local expansion and a slight perturbation leaves the arch without downstream support. This geometric principle does not rely on previously conjectured dynamical mechanisms and admits generalization to other agent-based and particulate systems.

A large population of motile agents can display remarkable collective behaviors. Here, we study collective motion of inertia-dominated macroscopic agents using a model system of millimeter-sized magnetic rollers with tunable motile behaviors. In this system, we observe first-order flocking phase separation, where a uniform flock propagates through an isotropic gaseous phase. The flocking phase and the coexisting gaseous phase exhibit distinct particle exchange dynamics and maintain different effective temperatures, which are unattainable in equilibrium systems. Combining experiments, agent-based simulations, and phenomenological theories, we demonstrate that inelastic collisions between inertial and externally driven magnetic rollers produce positive feedback between high density and polar motion, driving flocking phase separation. Our Letter reveals a novel mode of collective motion in inertial active matter, with potential implications for controlling biological flocks and designing robotic swarms.

The study of meson pairs produced with quantum correlations gives direct access to parameters that are challenging to measure in other systems. In this Letter, the existence of quantum correlations due to charge-conjugation symmetry $C$ are demonstrated in $D\overline{D}$ pairs produced through the processes $e^{+}{e}^{-}\to D\overline{D}$, $e^{+}{e}^{-}\to D^{*}\overline{D}$, and $e^{+}{e}^{-}\to D^{*}{\overline{D}}^{*}$, where the lack of charge superscripts refers to an admixture of neutral-charm-meson particle and antiparticle states, using $7.13{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected by the BESIII experiment between center-of-mass energies of 4.13–4.23 GeV. Processes with either $C$-even or $C$-odd constraints are identified and separated. A procedure is presented that harnesses the entangled production process to enable measurements of $D^0$-meson hadronic parameters. This Letter provides the first confirmation of quantum correlations in $e^{+}{e}^{-}\to XD\overline{D}$ processes and the first observation of a $C$-even constrained $D\overline{D}$ system. The procedure is applied to measure ${\delta }_{K\pi }^D$, the strong phase between the $D^0\to K^{-}{\pi }^{+}$ and ${\overline{D}}^0\to K^{-}{\pi }^{+}$ decay amplitudes, which results in the determination of ${\delta }_{K\pi }^D=({192.8}_{-12.4-2.4}^{+11.0+1.9})°$. The potential for measurements of other hadronic decay parameters and charm mixing with these and future datasets is also discussed.

Recent experiments have shown that raising the temperature of a dipolar gas under certain conditions leads to a transition to a supersolid state. Here, we employ the path integral Monte Carlo method, which exactly accounts for both thermal and correlation effects, to study that phenomenology in a system of ${}^{162}\mathrm{Dy}$ atoms in the canonical ensemble. Our microscopic description allows the quantitative characterization of the emergence of spatial order and superfluidity, the two ingredients that define a supersolid state. Our calculations prove that temperature on its own can promote the formation of a supersolid in a dipolar system. Furthermore, we bridge this exotic phenomenology with the more usual melting of the supersolid at a higher temperature. Our results offer insight into the interplay between thermal excitations, the dipole-dipole interaction, quantum statistics, and supersolidity.

We present a comprehensive theoretical investigation of magnetoelectric (ME) coupling mechanisms in 19 altermagnetic and 4 ferrimagnetic type-I multiferroics using electronic band structure calculations with spin-orbit coupling, a first-principles ME response framework, and spin-space-group theory analysis. We formulate a universal scheme for realizing nonvolatile ME coupling in type-I multiferroics, where two distinct pathways emerge, each dictated by spin-space symmetry. The first pathway is associated with switching of the spin splitting or the now familiar spin-momentum locking in reciprocal space, characteristic of some altermagnetic multiferroics that exhibit coexisting antiferromagnetism and ferroelectricity. The second pathway involves real-space magnetization switching via electric polarization reversal, characterized by switchable components of the linear ME tensor, despite the traditionally weak coupling in type-I systems due to the independent origins of magnetism and ferroelectricity. We demonstrate that these two intrinsic ME coupling mechanisms are mutually exclusive and propose thermodynamically stable compounds for experimentation. Our findings establish general design principles for controlling robust nonvolatile ME effects in multiferroic materials.

We analyze the precision of generic currents in a multiterminal quantum-transport setting. Employing scattering theory, we show that the precision of such currents is limited by a function of the particle-current noise that can be interpreted as the activity in the classical limit. We thereby establish a kinetic uncertainty relation for quantum transport. In the full quantum limit, we find precision bounds with modified activity constraints depending on whether the system is fermionic or bosonic. We expect these bounds to be suitable as guidelines for any transport process aiming at high precision.