Understanding singularities in ordered structures, such as dislocations in lattice modulation and solitons in charge ordering, offers great opportunities to disentangle the interactions between the electronic degrees of freedom and the lattice. Specifically, a modulated structure has traditionally been expressed in the form of a discrete Fourier series with a constant phase and amplitude for each component. Here, we report atomic scale observation and analysis of a new modulation wave in hole-doped ${\mathrm{LuFe}}_2{\mathrm{O}}_{4+\delta }$ that requires significant modifications to the conventional modeling of ordered structures. This new modulation with an unusual quasiperiodic singularity can be accurately described only by introducing a well-defined secondary modulation vector in both the phase and amplitude parameter spaces. Correlated with density-functional-theory (DFT) calculations, our results reveal that those singularities originate from the discontinuity of lattice displacement induced by interstitial oxygen in the system. The approach of our work is applicable to a wide range of ordered systems, advancing our understanding of the nature of singularity and modulation.

The pressure evolution of the Raman active electronic excitations of the transition metal dichalcogenides $2H\text{−}{\mathrm{TaS}}_2$ is followed through the pressure phase diagram embedding incommensurate charge-density-wave and superconducting states. At high pressure, the charge-density wave is found to collapse at 8.5 GPa. In the coexisting charge-density-wave and superconducting orders, we unravel a strong in-gap superconducting mode, attributed to a Higgs mode, coexisting with the expected incoherent Cooper-pair breaking signature. The latter remains in the pure superconducting state reached above 8.5 GPa. Our report constitutes a new observation of such Raman active Higgs mode since the long-standing unique case $2H\text{−}{\mathrm{NbSe}}_2$.

In this Letter, we show that the Shore-Johnson axioms for the maximum entropy principle in statistical estimation theory account for a considerably wider class of entropic functional than previously thought. Apart from a formal side of the proof where a one-parameter class of admissible entropies is identified, we substantiate our point by analyzing the effect of weak correlations and by discussing two pertinent examples: two-qubit quantum system and transverse-momentum behavior of hadrons in high-energy proton-proton collisions.

We explore the space of renormalization group flows that originate from supersymmetric $\mathcal{N}=1$ $SU(2)$ gauge theory with one adjoint and a pair of fundamental chiral multiplets. By considering all possible relevant deformations—including coupling to gauge-singlet chiral multiplets—we find 34 fixed points in this simple setup. We observe that theories in this class exhibit many novel phenomena: emergent symmetry, decoupling of operators, and narrow distribution of central charges $a/c$. This set of theories includes two of the $\mathcal{N}=2$ minimal Argyres-Douglas theories and their mass deformed versions. In addition, we find 36 candidate fixed point theories possessing unphysical fermionic operators—including one with central charges $(a,c)\simeq (0.20,0.22)$ that are smaller than any known superconformal theory—that need further investigation.

Prescaling is a far-from-equilibrium phenomenon which describes the rapid establishment of a universal scaling form of distributions much before the universal values of their scaling exponents are realized. We consider the example of the spatiotemporal evolution of the quark-gluon plasma explored in heavy-ion collisions at sufficiently high energies. Solving QCD kinetic theory with elastic and inelastic processes, we demonstrate that the gluon and quark distributions very quickly adapt a self-similar scaling form, which is independent of initial condition details and system parameters. The dynamics in the prescaling regime is then fully encoded in a few time-dependent scaling exponents, whose slow evolution gives rise to far-from-equilibrium hydrodynamic behavior.

We consider quarkyonic matter to naturally explain the observed properties of neutron stars. We argue that such matter might exist at densities close to that of nuclear matter, and at the onset, the pressure and the sound velocity in quarkyonic matter increase rapidly. In the limit of large number of quark colors $N_c$, this transition is characterized by a discontinuous change in pressure as a function of baryon number density. We make a simple model of quarkyonic matter and show that generically the sound velocity is a nonmonotonic function of density—it reaches a maximum at relatively low density, decreases, and then increases again to its asymptotic value of $1/\sqrt{3}$.

We consider two-dimensional spin-orbit-coupled atomic Bose-Einstein condensate in a radially periodic potential. The system supports different types of stable self-sustained states including radially symmetric vorticity-carrying modes with different topological charges in two spinor components that may have multiring profiles and at the same time remain remarkably stable for repulsive interactions. Solitons of the second type show persistent rotation with constant angular frequency. They can be stable for both repulsive and attractive interatomic interactions. Because of the inequivalence between clockwise and counterclockwise rotation directions introduced by spin-orbit coupling, the properties of such solitons strongly differ for positive and negative rotation frequencies. The collision of solitons located in the same or different rings is accompanied by a change of the rotation frequency that depends on the phase difference between colliding solitons.

We have developed an approach to continuously load ultracold ${}^{85}{\mathrm{Rb}}_2$ vibrational ground-state molecules into a crossed optical dipole trap from a magneto-optical trap. The technique relies on a single high-power light beam with a broad spectrum superimposed onto a narrow peak at an energy of about $9400{\mathrm{cm}}^{-1}$. This single laser source performs all the required steps: the short-range photoassociation creating ground-state molecules after radiative emission, the cooling of the molecular vibrational population down to the lowest vibrational level $v_X=0$, and the optical trapping of these molecules. Furthermore, we probe by depletion spectroscopy and determine that 75% of the $v_X=0$ ground-state molecules are in the three lowest rotational levels $J_X=0$, 1, 2. The lifetime of the ultracold molecules in the optical dipole trap is limited to about 70 ms by off-resonant light scattering. The proposed technique opens perspectives for the formation of new molecular species in the ultracold domain, which are not yet accessible by well-established approaches.

Classical nonlinear waves exhibit a phenomenon of condensation that results from the natural irreversible process of thermalization, in analogy with the quantum Bose-Einstein condensation. Wave condensation originates in the divergence of the thermodynamic equilibrium Rayleigh-Jeans distribution, which is responsible for the macroscopic population of the fundamental mode of the system. However, achieving complete thermalization and condensation of incoherent waves through nonlinear optical propagation is known to require prohibitive large interaction lengths. Here, we derive a discrete kinetic equation describing the nonequilibrium evolution of the random wave in the presence of a structural disorder of the medium. Our theory reveals that a weak disorder accelerates the rate of thermalization and condensation by several order of magnitudes. Such a counterintuitive dramatic acceleration of condensation can provide a natural explanation for the recently discovered phenomenon of optical beam self-cleaning. Our experiments in multimode optical fibers report the observation of the transition from an incoherent thermal distribution to wave condensation, with a condensate fraction of up to 60% in the fundamental mode of the waveguide trapping potential.

Elastic waveguides with time-modulated stiffness feature a frequency-periodic dispersion spectrum, where branches merge at multiple integers of half the modulation frequency and over a finite wave number range. In this range, frequency becomes complex, with its real part remaining constant. The vanishing group velocity associated with these flat bands leads to frequency-selective reflection at an interface between a nonmodulated medium and a time-modulated one, which converts a broadband input into a narrow-band output centered at the half modulation frequency. This behavior is illustrated in an elastic waveguide in transverse motion, where modulation is implemented experimentally by an array of piezoelectric patches shunted through a negative electrical capacitance controlled by a switching circuit. The switching schedule defines the modulation frequency and allows the selection of the output frequency. This implementation is suitable for the investigation of numerous properties of time-space modulated elastic metamaterials, such as nonreciprocity and one-way propagation, and can lead to the implementation of novel functionalities for acoustic wave devices operating on piezoelectric substrates.

We address the nature of spin transport in the integrable $XXZ$ spin chain, focusing on the isotropic Heisenberg limit. We calculate the diffusion constant using a kinetic picture based on generalized hydrodynamics combined with Gaussian fluctuations: we find that it diverges, and show that a self-consistent treatment of this divergence gives superdiffusion, with an effective time-dependent diffusion constant that scales as $D(t)\sim t^{1/3}$. This exponent had previously been observed in large-scale numerical simulations, but had not been theoretically explained. We briefly discuss $XXZ$ models with easy-axis anisotropy $\mathrm{\Delta }>1$. Our method gives closed-form expressions for the diffusion constant $D$ in the infinite-temperature limit for all $\mathrm{\Delta }>1$. We find that $D$ saturates at large anisotropy, and diverges as the Heisenberg limit is approached, as $D\sim (\mathrm{\Delta }-1{)}^{-1/2}$.

Fluids in which both time reversal and parity are broken can display a dissipationless viscosity that is odd under each of these symmetries. Here, we show how this odd viscosity has a dramatic effect on topological sound waves in fluids, including the number and spatial profile of topological edge modes. Odd viscosity provides a short-distance cutoff that allows us to define a bulk topological invariant on a compact momentum space. As the sign of odd viscosity changes, a topological phase transition occurs without closing the bulk gap. Instead, at the transition point, the topological invariant becomes ill defined because momentum space cannot be compactified. This mechanism is unique to continuum models and can describe fluids ranging from electronic to chiral active systems.

Microflows constitute an important instrument to control particle dynamics. A prominent example is the sorting of biological cells, which relies on the ability of deformable cells to move transversely to flow lines. A classic result is that soft microparticles migrate in flows through straight microchannels to an attractor at their center. Here, we show that flows through wavy channels fundamentally change the overall picture. They lead to the emergence of a second, coexisting attractor for soft particles. Its emergence and off-center location depends on the boundary modulation and the particle properties. The related cross-stream migration of soft particles is explained by analytical considerations, Stokesian dynamics simulations in unbounded flows, and Lattice-Boltzmann simulations in bounded flows. The novel off-center attractor can be used, for instance, in diagnostics, for separating cells of different size and elasticity, which is often an indicator of their health status.

We report on spontaneous rotational symmetry breaking in a minimal model of complex macromolecules with branches and cycles. The transition takes place as the strength of the self-repulsion is increased. At the transition point, the density distribution transforms from isotropic to anisotropic. We analyze this transition using a variational mean-field theory that combines the Gibbs-Bogolyubov-Feynman inequality with the concept of the Laplacian matrix. The density distribution of the broken symmetry state is shown to be determined by the eigenvalues and eigenvectors of this Laplacian matrix. Physically, this reflects the increasing role of the underlying topological structure in determining the density of the macromolecule when repulsive interactions generate internal tension. Eventually, the variational free energy landscape develops a complex structure with multiple competing minima.

Using $e^{+}{e}^{-}$ annihilation data corresponding to an integrated luminosity of $3.19{\mathrm{fb}}^{-1}$ collected at a center-of-mass energy of 4.178 GeV with the BESIII detector, we measure the absolute branching fractions ${\mathcal{B}}_{D_s^{+}\to \eta e^{+}{\nu }_e}=(2.323\pm {0.063}_{\text{stat}}\pm {0.063}_{\text{syst}})\%$ and ${\mathcal{B}}_{D_s^{+}\to {\eta }^{\prime }{e}^{+}{\nu }_e}=(0.824\pm {0.073}_{\text{stat}}\pm {0.027}_{\text{syst}})\%$ via a tagged analysis technique, where one $D_s$ is fully reconstructed in a hadronic mode. Combining these measurements with previous BESIII measurements of ${\mathcal{B}}_{D^{+}\to {\eta }^{(\prime )}{e}^{+}{\nu }_e}$, the $\eta -{\eta }^{\prime }$ mixing angle in the quark flavor basis is determined to be ${\varphi }_P=(40.1\pm 2.1_{\text{stat}}\pm 0.7_{\text{syst}})°$. From the first measurements of the dynamics of $D_s^{+}\to {\eta }^{(\prime )}{e}^{+}{\nu }_e$ decays, the products of the hadronic form factors $f_{+}^{{\eta }^{(\prime )}}(0)$ and the Cabibbo-Kobayashi-Maskawa matrix element $|V_{\mathrm{cs}}|$ are determined with different form factor parametrizations. For the two-parameter series expansion, the results are $f_{+}^{\eta }(0)|V_{cs}|=0.4455\pm {0.0053}_{\text{stat}}\pm {0.0044}_{\text{syst}}$ and $f_{+}^{{\eta }^{\prime }}(0)|V_{\mathrm{cs}}|=0.477\pm {0.049}_{\text{stat}}\pm {0.011}_{\text{syst}}$.

A multifaceted first-principles approach utilizing density functional theory, evolutionary algorithms, and lattice dynamics was used to construct the phase diagram of silicon up to 4 TPa and $26000\text{K}$. These calculations predicted that (i) an anomalous sequence of face-centered cubic to body-centered cubic to simple cubic crystalline phase transitions occur at pressures of 2.87 and 3.89 TPa, respectively, along the cold curve, (ii) the orthorhombic phases of Imma and Cmce-16 appear on the phase diagram only when the anharmonic contribution to the Gibbs free energy is taken into account, and (iii) a substantial change in the slope of the principal Hugoniot is observed if the anharmonic free energy of the cubic diamond phase is considered.