Molecular crystals are increasingly being used for advanced applications, ranging from pharmaceutics to organic electronics, with their utility dictated by a combination of their three-dimensional structures and molecular dynamics—with anharmonicity in the low-frequency vibrations crucial to numerous bulk phenomena. Through the use of temperature-dependent x-ray diffraction and terahertz time-domain spectroscopy, the structures and dynamics of a pair of isomeric molecular crystals exhibiting nearly free rotation of a ${\mathrm{CF}}_3$ functional group at ambient conditions are fully characterized. Using a recently developed solid-state anharmonic vibrational correction, and applying it to a molecular crystal for the first time, the temperature-dependent spatial displacements of atoms along particular terahertz modes are obtained, and are found to be in excellent agreement with the experimental observations, including the assignment of a previously unexplained absorption feature in the low-frequency spectrum of one of the solids.

In this Letter, we present a universal approach enabling the full characterization of the quantum properties of a multimode optical system in terms of squeezing and morphing supermodes. These are modes undergoing a continuous evolution that allow uncoupling the system dynamics in terms of statistically independent physical observables. This dynamical feature, never considered so far, enables the description and investigation of an extremely broad variety of key resources for experimental quantum optics, ranging from optical parametric oscillators to silicon-based microring resonators, as well as optomechanical systems.

We study a hitherto unexplored regime of the Rydberg excitation blockade using highly Stark-shifted, yet long-living, states of Rb atoms subject to electric fields above the classical ionization limit. Such states allow tuning the dipole-dipole interaction strength while their ionization rate can be changed over 2 orders of magnitude by small variations of the electric field. We demonstrate laser excitation of the interacting Rydberg states followed by their detection using controlled ionization and magnified imaging with high spatial and temporal resolution. Our work reveals new possibilities to engineer the interaction strength and dynamically control the ionization and detection of Rydberg atoms, which can be useful for realizing and assessing quantum simulators that vary in space and time.

How weak is the weak turbulence? Here, we analyze turbulence of weakly interacting waves using the tools of information theory. It offers a unique perspective for comparing thermal equilibrium and turbulence. The mutual information between modes is stationary and small in thermal equilibrium, yet it is shown here to grow with time for weak turbulence in a finite box. We trace this growth to the concentration of probability on the resonance surfaces, which can go all the way to a singular measure. The surprising conclusion is that no matter how small is the nonlinearity and how close to Gaussian is the statistics of any single amplitude, a stationary phase-space measure is far from Gaussian, as manifested by a large relative entropy. This is a rare piece of good news for turbulence modeling: the resolved scales carry significant information about the unresolved scales. The mutual information between large and small scales is the information capacity of turbulent cascade, setting the limit on the representation of subgrid scales in turbulence modeling.

Shock release from inertial confinement fusion (ICF) shells poses a great challenge to single-fluid hydrodynamic equations, especially for describing materials composed of different ion species. This has been evidenced by a recent experiment [Haberberger et al., Phys. Rev. Lett. 123, 235001 (2019)], in which low-density plasmas (${10}^{19}$ to ${10}^{20}{\mathrm{cm}}^{-3}$) are measured to move far ahead of what radiation-hydrodynamic simulations predict. To understand such experimental observations, we have performed large-scale nonequilibrium molecular-dynamics simulations of shock release in polystyrene (CH) at experimental conditions. These simulations revealed that upon shock releasing from the back surface of a CH foil, hydrogen can stream out of the bulk of the foil due to its mass being lighter than carbon. This released hydrogen, exhibiting a much broader velocity distribution than carbon, forms low-density plasmas moving in nearly constant velocities ahead of the in-flight shell, which is in quantitative agreement with the experimental measurements. Such kinetic effect of species separation is currently missing in single-fluid radiation-hydrodynamics codes for ICF simulations.

Isolated linear carbon chains (LCCs) encapsulated by multiwalled carbon nanotubes are studied under hydrostatic pressure ($P$) via resonance Raman scattering. The LCCs’ spectroscopic signature C band around $1850{\mathrm{cm}}^{-1}$ softens linearly with increasing $P$. A simple anharmonic force-constant model not only describes such softening but also shows that the LCCs’ Young’s modulus ($E$), Grüneisen parameter ($\gamma$), and strain ($ϵ$) follow universal $P^{-1}$ and $P^2$ laws, respectively. In particular, $\gamma$ also presents a unified behavior for all LCCs. To the best of our knowledge, these are the first results reported on such isolated systems and the first work to explore universal $P$-dependent responses for LCCs’ $E$, $ϵ$, and $\gamma$.

Electron-phonon interactions are key to understanding the dynamics of electrons in materials and can be modeled accurately from first principles. However, when electrons and holes form Coulomb-bound states (excitons), quantifying their interactions and scattering processes with phonons remains an open challenge. Here we show a rigorous approach for computing exciton-phonon (ex-ph) interactions and the associated exciton dynamical processes from first principles. Starting from the ab initio Bethe-Salpeter equation, we derive expressions for the ex-ph matrix elements and relaxation times. We apply our method to bulk hexagonal boron nitride, for which we map the ex-ph relaxation times as a function of exciton momentum and energy, analyze the temperature and phonon-mode dependence of the ex-ph scattering processes, and accurately predict the phonon-assisted photoluminescence. The approach introduced in this work is general and provides a framework for investigating exciton dynamics in a wide range of materials.

Finite dimensional signatures of spinodal criticality are notoriously difficult to come by. The dynamical transition of glass-forming liquids, first described by mode-coupling theory, is a spinodal instability preempted by thermally activated processes that also limit how close the instability can be approached. We combine numerical tools to directly observe vestiges of the spinodal criticality in finite dimensional glass formers. We use the swap Monte Carlo algorithm to efficiently thermalize configurations beyond the mode-coupling crossover, and analyze their dynamics using a scheme to screen out activated processes, in spatial dimensions ranging from $d=3$ to $d=10$. We observe a strong softening of the mean-field square-root singularity in $d=3$ that is progressively restored as $d$ increases above $d=8$, in surprisingly good agreement with perturbation theory.

High-dimensional entanglement promises to greatly enhance the performance of quantum communication and enable quantum advantages unreachable by qubit entanglement. One of the great challenges, however, is the reliable production, distribution, and local certification of high-dimensional sources of entanglement. In this Letter, we present an optical setup capable of producing quantum states with an exceptionally high level of scalability, control, and quality that, together with novel certification techniques, achieve the highest amount of entanglement recorded so far. We showcase entanglement in 32-spatial dimensions with record fidelity to the maximally entangled state ($F=0.933\pm 0.001$) and introduce measurement efficient schemes to certify entanglement of formation ($E_{oF}=3.728\pm 0.006$). Combined with the existing multicore fiber technology, our results will lay a solid foundation for the construction of high-dimensional quantum networks.

Many theories predict the existence of very heavy compact objects, that in terms of sizes would belong to the realms of nuclear or atomic physics, but in terms of masses could extend to the macroscopic world, reaching kilograms, tonnes, or more. If they exist, it is likely that they reach our planet with high speeds and cross the atmosphere. Because of their high mass-to-size ratio and huge energy, in many cases, they would leave behind a trail in the form of sound and seismic waves, etches, or light in transparent media. Here we show results of a search for such objects in visual photographs of the sky taken by the “Pi of the Sky” experiment, illustrated with the most stringent limits on the isotropic flux of incoming so-called nuclearites, spanning between $5.4\times {10}^{-20}$ and $2.2\times {10}^{-21}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}{\mathrm{sr}}^{-1}$ for masses between 100 g and 100 kg. In addition we establish a directional flux limit under an assumption of a static “sea” of nuclearites in the Galaxy, which spans between $1.5\times {10}^{-18}$ and $2.1\times {10}^{-19}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ in the same mass range. The general nature of the limits presented should allow one to constrain many specific models predicting the existence of heavy compact objects and both particle physics and astrophysical processes leading to their creation, and their sources.

Hadronic vacuum polarization (HVP) is not only a critical part of the standard model (SM) prediction for the anomalous magnetic moment of the muon $(g-2{)}_{\mu }$, but also a crucial ingredient for global fits to electroweak (EW) precision observables due to its contribution to the running of the fine-structure constant encoded in $\mathrm{\Delta }{\alpha }_{\text{had}}^{(5)}$. We find that with modern EW precision data, including the measurement of the Higgs mass, the global fit alone provides a competitive, independent determination of $\mathrm{\Delta }{\alpha }_{\text{had}}^{(5)}{|}_{\mathrm{EW}}=270.2(3.0)\times {10}^{-4}$. This value actually lies below the range derived from $e^{+}{e}^{-}\to \text{hadrons}$ cross section data, and thus goes into the opposite direction as would be required if a change in HVP were to bring the SM prediction for $(g-2{)}_{\mu }$ into agreement with the Brookhaven measurement. Depending on the energy where the bulk of the changes in the cross section occurs, reconciling experiment and SM predictions for $(g-2{)}_{\mu }$ by adjusting HVP would thus not necessarily weaken the case for physics beyond the SM (BSM), but to some extent shift it from $(g-2{)}_{\mu }$ to the EW fit. We briefly explore some options of BSM scenarios that could conceivably explain the ensuing tension.

Feshbach resonances corresponding to metastable vibrational states of the dipole-bound state (DBS) have been interrogated in real time for the first time. The state-specific autodetachment rates of the DBS of the phenoxide anion in the cryogenically cooled ion trap have been directly measured, giving $\tau \sim 33.5\mathrm{ps}$ for the lifetime of the most prominent ${11}^{\prime 1}$ mode ($519{\mathrm{cm}}^{-1}$). Overall, the lifetime of the individual DBS state is strongly mode dependent to give $\tau \sim 5\mathrm{ps}$ for the ${18}^{\prime 1}$ mode ($632{\mathrm{cm}}^{-1}$) and $\tau \sim 12\mathrm{ps}$ for the ${11}^{\prime 2}$ mode ($1036{\mathrm{cm}}^{-1}$). The qualitative trend of the experiment could be successfully explained by the Fermi’s golden rule. Autodetachment of the ${11}^{\prime 1}{18}^{\prime 1}$ combination mode is found to be much accelerated ($\tau \le 1.4\mathrm{ps}$) than expected, and its bifurcation dynamics into either the ${11}^1{18}^0$ or ${11}^0{18}^1$ state of the neutral core radical, according to the propensity rule of $\mathrm{\Delta }v=-1$, could be distinctly differentiated through the photoelectron images to provide the unprecedented deep insights into the interaction between electronic and nuclear dynamics of the DBS, challenging the most sophisticated theoretical calculations.

We present a protocol to deterministically prepare the electromagnetic field in a large photon number state. The field starts in a coherent state and, through resonant interaction with one or few two-level systems, it evolves into a coherently displaced Fock state without any postselection. We show the feasibility of the scheme under realistic parameters. The presented method opens a door to reach Fock states, with $n\sim 100$ and optimal fidelities above 70%, blurring the line between macroscopic and quantum states of the field.

We investigate the full quantum evolution of ultracold interacting bosonic atoms on a chain and coupled to an optical cavity. Extending the time-dependent matrix product state techniques and the many-body adiabatic elimination technique to capture the global coupling to the cavity mode and the open nature of the cavity, we examine the long time behavior of the system beyond the mean-field elimination of the cavity field. We investigate the many-body steady states and the self-organization transition for a wide range of parameters. We show that in the self-organized phase the steady state consists in a mixture of the mean-field predicted density wave states and excited states with additional defects. In particular, for large dissipation strengths a steady state with a fully mixed atomic sector is obtained crucially different from the predicted mean-field state.

We present theoretical and experimental evidence of an anomalous surface corrugation behavior in He-KCl(001) for incidence along $⟨110⟩$. When the He normal energy decreases below 100 meV, i.e., He-surface distances $Z>2\AA$, the corrugation unexpectedly increases up to an impressive $\gtrsim 85\%$. This is not due to van der Waals interactions but to the combination of soft potential effects and the evolution of He-cation and He-anion interactions with $Z$. This feature, not previously analyzed on alkali-halide surfaces, may favor the alignment properties of weakly interacting overlayers.

Effects of electron many-body interactions amplify in an electronic system with a narrow bandwidth opening a way to exotic physics. A narrow band in a two-dimensional (2D) honeycomb lattice is particularly intriguing as combined with Dirac bands and topological properties but the material realization of a strongly interacting honeycomb lattice described by the Kane-Mele-Hubbard model has not been identified. Here we report a novel approach to realize a 2D honeycomb-lattice narrow-band system with strongly interacting $5d$ electrons. We engineer a well-known triangular lattice 2D Mott insulator $1T\text{−}{\mathrm{TaS}}_2$ into a honeycomb lattice utilizing an adsorbate superstructure. Potassium (K) adatoms at an optimum coverage deplete one-third of the unpaired $d$ electrons and the remaining electrons form a honeycomb lattice with a very small hopping. Ab initio calculations show extremely narrow $Z_2$ topological bands mimicking the Kane-Mele model. Electron spectroscopy detects an order of magnitude bigger charge gap confirming the substantial electron correlation as confirmed by dynamical mean field theory. It could be the first artificial Mott insulator with a finite spin Chern number.

Superconductivity arises from two distinct quantum phenomena: electron pairing and long-range phase coherence. In conventional superconductors, the two quantum phenomena generally take place simultaneously, while in the underdoped high- $T_c$ cuprate superconductors, the electron pairing occurs at higher temperature than the long-range phase coherence. Recently, whether electron pairing is also prior to long-range phase coherence in single-layer FeSe film on ${\mathrm{SrTiO}}_3$ substrate is under debate. Here, by measuring Knight shift and nuclear spin-lattice relaxation rate, we unambiguously reveal a pseudogap behavior below $T_p\sim 60\mathrm{K}$ in two kinds of layered FeSe-based superconductors with quasi2D nature. In the pseudogap regime, a weak diamagnetic signal and a remarkable Nernst effect are also observed, which indicates that the observed pseudogap behavior is related to superconducting fluctuations. These works confirm that strong phase fluctuation is an important character in the 2D iron-based superconductors as widely observed in high-$T_c$ cuprate superconductors.

Giant second-harmonic generation in the terahertz (THz) frequency range is observed in a thin film of an $s$-wave superconductor NbN, where the time-reversal ($\mathcal{T}$) and space-inversion ($\mathcal{P}$) symmetries are simultaneously broken by supercurrent injection. We demonstrate that the phase of the second-harmonic signal flips when the direction of supercurrent is inverted; i.e., the signal is ascribed to the nonreciprocal response that occurs under broken $\mathcal{P}$ and $\mathcal{T}$ symmetries. The temperature dependence of the SH signal exhibits a sharp resonance, which is accounted for by the vortex motion driven by the THz electric field in an anharmonic pinning potential. The maximum conversion ratio ${\eta }_{\mathrm{SHG}}$ reaches $\approx {10}^{-2}$ in a thin film NbN with the thickness of 25 nm after the field cooling with a very small magnetic field of $\approx 1\mathrm{Oe}$, for a relatively weak incident THz electric field of $2.8\mathrm{kV}/\mathrm{cm}$ at 0.48 THz.

We report muon spin rotation and magnetic susceptibility experiments on in-plane stress effects on the static spin-stripe order and superconductivity in the cuprate system ${\mathrm{La}}_{2-x}{\mathrm{Ba}}_x{\mathrm{CuO}}_4$ with $x=0.115$. An extremely low uniaxial stress of $\sim 0.1\mathrm{GPa}$ induces a substantial decrease in the magnetic volume fraction and a dramatic rise in the onset of 3D superconductivity, from $\sim 10$ to 32 K; however, the onset of at-least-2D superconductivity is much less sensitive to stress. These results show not only that large-volume-fraction spin-stripe order is anticorrelated with 3D superconducting coherence but also that these states are energetically very finely balanced. Moreover, the onset temperatures of 3D superconductivity and spin-stripe order are very similar in the large stress regime. These results strongly suggest a similar pairing mechanism for spin-stripe order and the spatially modulated 2D and uniform 3D superconducting orders, imposing an important constraint on theoretical models.