We investigate the interaction between nonclassical light with a tunable multiphoton component and a highly nonlinear medium based on cold Rydberg atoms. The nonclassical field emitted by a DLCZ quantum memory is stored using Rydberg electromagnetically induced transparency, experiencing strong nonlinear response due to the dipole blockade. We show that the storage efficiency in the Rydberg ensemble decreases as a function of the multiphoton strength of the input field, as a result of the nonlinearity. We also show that the autocorrelation function $g^{(2)}(0)$ of the retrieved field after storage in the Rydberg state is considerably reduced, leading to the first demonstration of single photon filtering with nonclassical input light. Finally, we develop a simple simulation that allows us to model the effect of our medium on the input state. This work is a step towards matter-mediated photon-photon interactions with nonclassical light.

In this Letter, we investigate the ground state properties of an optomechanical system consisting of a coupled cavity and mechanical modes. An exact solution is given when the ratio $\eta$ between the cavity and mechanical frequencies tends to infinity. This solution reveals a coherent photon occupation in the ground state by breaking continuous or discrete symmetries, exhibiting an equilibrium quantum phase transition (QPT). In the U(1)-broken phase, an unstable Goldstone mode can be excited. In the model featuring $Z_2$ symmetry, we discover the mutually (in the finite $\eta$) or unidirectionally (in $\eta \to \infty$) dependent relation between the squeezed vacuum of the cavity and mechanical modes. In particular, when the cavity is driven by a squeezed field along the required squeezing parameter, it enables modifying the region of $Z_2$-broken phase and significantly reducing the coupling strength to reach QPTs. Furthermore, by coupling atoms to the cavity mode, the hybrid system can undergo a QPT at a hybrid critical point, which is cooperatively determined by the optomechanical and light-atom systems. These results suggest that this optomechanical system complements other phase transition models for exploring novel critical phenomena.

The interaction of a resonant light field with a quantum two-level system is of key interest both for fundamental quantum optics and quantum technological applications employing resonant excitation. While emission under resonant continuous-wave excitation has been well studied, the more complex emission spectrum of dynamically dressed states—a quantum two-level system driven by resonant pulsed excitation—has so far been investigated in detail only theoretically. Here, we present the first experimental observation of the complete resonance fluorescence emission spectrum of a single quantum two-level system, in the form of an excitonic transition in a semiconductor quantum dot, driven by finite Gaussian pulses. We observe multiple emerging sidebands as predicted by theory, with an increase of their number and spectral detuning with excitation pulse intensity and a dependence of their spectral shape and intensity on the pulse length. Detuning-dependent measurements provide additional insights into the emission features. The experimental results are in excellent agreement with theoretical calculations of the emission spectra, corroborating our findings.

The thickness of freshly made soap films is usually in the micron range, and interference colors make thickness fluctuations easily visible. Circular patterns of constant thickness are commonly observed, either a thin film disc in a thicker film or the reverse. In this Letter, we evidence the line tension at the origin of these circular patterns. Using a well controlled soap film preparation, we produce a piece of thin film surrounded by a thicker film. The thickness profile, measured with a spectral camera, leads to a line tension of the order of ${10}^{-10}\mathrm{N}$ which drives the relaxation of the thin film shape, initially very elongated, toward a circular shape. A balance between line tension and air friction leads to a quantitative prediction of the relaxation process. Such a line tension is expected to play a role in the production of marginal regeneration patches, involved in soap film drainage and stability.

We examine theoretically the inertial migration of a neutrally buoyant rigid sphere in pressure-driven channel flow, accounting for its finite size relative to the channel width (the confinement ratio). For sufficiently large channel Reynolds numbers (${\mathrm{Re}}_c$), a small but finite confinement ratio qualitatively alters the inertial lift velocity profiles obtained using a point-particle formulation. Finite size effects lead to new equilibria, in addition to the well-known Segre-Silberberg pinch locations. Consequently, a sphere can migrate to either the near-wall Segre-Silberberg equilibria, or the new stable equilibria located closer to the channel centerline, depending on ${\mathrm{Re}}_c$ and its initial position. Our findings are in accord with recent experiments and simulations, and have implications for passive sorting of particles based on size, shape, and other physical characteristics, in microfluidic applications.

Friction is responsible for about one-third of the primary energy consumption in the world. So far, a thorough atomistic understanding of the frictional energy dissipation mechanisms is still lacking. The Amontons’ law states that kinetic friction is independent of the sliding velocity while the Prandtl-Tomlinson model suggests that damping is proportional to the relative sliding velocity between two contacting objects. Through careful analysis of the energy dissipation process in atomic force microscopy measurements, here we propose that damping force is proportional to the tip oscillation speed induced by friction. It is shown that a physically well-founded damping term can better reproduce the multiple peaks in the velocity-dependent friction force observed in both experiments and molecular dynamics simulations. Importantly, the analysis gives a clear physical picture of the dynamics of energy dissipation in different friction phases, which provides insight into long-standing puzzles in sliding friction, such as velocity weakening and spring-stiffness-dependent friction.

A generation, propagation, and transfer of phonon angular momenta are examined on thermal transport in chiral insulative and diamagnetic crystals of $\alpha$-quartz. We found that thermally driven phonons carry chirality-dependent angular momenta in the quartz crystals and they could be extracted from the quartz as a spin signal. Namely, chirality-induced selectivity of phonon angular momenta is realized in the chiral quartz. We argue that chiral phonons available in chiral materials could be a key element in triggering or enhancing chirality-induced spin selectivity with robust spin polarization and long-range spin transport found in various chiral materials.

Employing flux-grown single crystal ${\mathrm{WSe}}_2$, we report charge-carrier scattering behaviors measured in $h$-BN encapsulated monolayer field effect transistors. We observe a nonmonotonic change of transport mobility as a function of hole density in the degenerately doped sample, which can be explained by energy dependent scattering amplitude of strong defects calculated using the T-matrix approximation. Utilizing long mean-free path ($>500\mathrm{nm}$), we also demonstrate the high quality of our electronic devices by showing quantized conductance steps from an electrostatically defined quantum point contact, showing the potential for creating ultrahigh quality quantum optoelectronic devices based on atomically thin semiconductors.

We synthesize a thin film composed of long carbyne chains terminated by gold clusters and study its optical properties. The presence of gold particles stabilizes longer chains and leads to their alignment. We show that the gold clusters also act as a source of electron doping, thus, changing the intensity of photoluminescence from quadratic dependence on the pumping intensity without gold to linear with gold. We also observe that the excitation of the film at the gold plasmon frequency causes the blue shift of photoluminescence and estimate, on the basis of this effect, the minimum length of the carbyne chains. The high degree of alignment of the gold-terminated carbyne chains results in strongly anisotropic light absorption characterized by a distinctive cosine dependence on the angle between the carbyne molecule and polarization plane of the excitation. This paves the way for a new class of ultimately thin polarization sensitive emitters to be used in future integrated quantum photonics devices.

We study the large-scale dynamics of charged particles in a rapidly oscillating field and formulate its classical and quantum effective theory description. The high-order perturbative results for the effective action are presented. Remarkably, the action models the effects of post-Newtonian general relativity on the motion of nonrelativistic particles, with the values of the emergent curvature and speed of light determined by the field spatial distribution and frequency. Our results can be applied to a wide range of physical problems including the high-precision analysis and design of the charged particle traps and Floquet quantum materials.

We demonstrate that the well-known 2.6 MeV gamma-ray emission line from thallium-208 could serve as a real-time indicator of astrophysical heavy element production, with both rapid ($r$) and intermediate ($i$) neutron capture processes capable of its synthesis. We consider the $r$ process in a Galactic neutron star merger and show Tl-208 to be detectable from $\sim 12$ hours to $\sim \mathrm{ten}$ days, and again $\sim 1–20\mathrm{years}$ postevent. Detection of Tl-208 represents the only identified prospect for a direct signal of lead production (implying gold synthesis), arguing for the importance of future MeV telescope missions which aim to detect Galactic events but may also be able to reach some nearby galaxies in the Local Group.

Bloch oscillations refer to the periodic oscillation of a wave packet in a lattice under a constant force. Typically, the oscillation has a fundamental period that corresponds to the wave packet traversing the first Brillouin zone once. Here, we demonstrate, both theoretically and experimentally, the optical Bloch oscillations where the wave packet must traverse the first Brillouin zone twice to complete a full cycle, resulting in a period of oscillation that is 2 times longer than that of usual Bloch oscillations. The unusual Bloch oscillations arise due to the band crossing of valley-Hall topological edge states at the Brillouin boundary for zigzag domain walls between two staggered honeycomb lattices with inverted on-site energy detuning, which are protected by the glide-reflection symmetry of the underlying structures. Our work sheds light on the direct detection of band crossings resulting from intrinsic symmetries that extend beyond the fundamental translational symmetry in topological systems.

Phase-sensitive measurements on a composite ring made of a superconductor of interest connected by a known singlet $s$-wave superconductor can unambiguously determine its pairing symmetry. In composite rings with epitaxial $\beta \text{−}{\mathrm{Bi}}_2\mathrm{Pd}$ and $s$-wave Nb, we have observed half-integer-quantum flux when Nb is connected to the opposite crystalline ends of $\beta \text{−}{\mathrm{Bi}}_2\mathrm{Pd}$ and integer-quantum flux when Nb is connected to the same crystalline ends of $\beta \text{−}{\mathrm{Bi}}_2\mathrm{Pd}$. With ascending temperature, the half-integer-flux quantization transits to integer-flux quantization, before the eventual loss of phase coherence. These findings point to odd-parity pairing symmetry in superconducting $\beta \text{−}{\mathrm{Bi}}_2\mathrm{Pd}$.

The slow transition from an out-of-equilibrium glass towards a supercooled liquid is a complex relaxation phenomenon. In this Letter, we study the correlation between mechanical relaxation and equilibration kinetics in a ${\text{Pd}}_{20}{\text{Pt}}_{20}{\text{Cu}}_{20}{\text{Ni}}_{20}{\mathrm{P}}_{20}$ high-entropy metallic glass. The evolution of stress relaxation with aging time was obtained with an unprecedented detail, allowing us to pinpoint new interesting features. The long structural relaxation towards equilibrium contains a wide distribution of activation energies, instead of being just associated to the $\beta$ relaxation as commonly accepted. The stress relaxation time can be correlated with the equilibration rate and we observe a decrease of microstructural heterogeneity which contrasts with an increase of dynamic heterogeneity. These results significantly enhance our insight of the interplay between relaxation dynamics and thermodynamics in metallic glasses.

We use photoemission electron microscopy to measure the ferroelastic twin wall angles at the surface of ${\mathrm{CaTiO}}_3$ (001) and deduce the strain ordering. We analyze the angular dependence of the photoelectron emission from different domain surfaces, each with its own characteristic tilt angle in the factory rooflike topography. By considering the surface topography as a field perturbation, the offset in the photoemission threshold can be directly related to the tilt angles. With knowledge of the symmetry allowed twin walls we quantify the twin angles between 179.1° to 180.8°.

Recent experiments reported an antisymmetric planar Hall effect, where the Hall current is odd in the in plane magnetic field and scales linearly with both electric and magnetic fields applied. Existing theories rely exclusively on a spin origin, which requires spin-orbit coupling to take effect. Here, we develop a general theory for the intrinsic planar Hall effect (IPHE), highlighting a previously unknown orbital mechanism and connecting it to a band geometric quantity—the anomalous orbital polarizability (AOP). Importantly, the orbital mechanism does not request spin-orbit coupling, so sizable IPHE can occur and is dominated by an orbital contribution in systems with weak spin-orbit coupling. Combined with first-principles calculations, we demonstrate our theory with quantitative evaluation for bulk materials ${\mathrm{TaSb}}_2$, ${\mathrm{NbAs}}_2$, and ${\mathrm{SrAs}}_3$. We further show that AOP and its associated orbital IPHE can be greatly enhanced at topological band crossings, offering a new way to probe topological materials.

The charge density wave (CDW) state of $2H\text{−}{\mathrm{NbSe}}_2$ features commensurate domains separated by domain boundaries accompanied by phase slips known as discommensurations. We have unambiguously visualized the structure of CDW domains using a displacement-field measurement algorithm on a scanning tunneling microscopy image. Each CDW domain is delimited by three vertices and three edges of discommensurations and is designated by a triplet of integers whose sum identifies the types of commensurate structure. The observed structure is consistent with the alternating triangular tiling pattern predicted by a phenomenological Landau theory. The domain shape is affected by crystal defects and also by topological defects in the CDW phase factor. Our results provide a foundation for a complete understanding of the CDW state and its relation to the superconducting state.

Multivariate functions of continuous variables arise in countless branches of science. Numerical computations with such functions typically involve a compromise between two contrary desiderata: accurate resolution of the functional dependence, versus parsimonious memory usage. Recently, two promising strategies have emerged for satisfying both requirements: (i) The quantics representation, which expresses functions as multi-index tensors, with each index representing one bit of a binary encoding of one of the variables; and (ii) tensor cross interpolation (TCI), which, if applicable, yields parsimonious interpolations for multi-index tensors. Here, we present a strategy, quantics TCI, which combines the advantages of both schemes. We illustrate its potential with an application from condensed matter physics: the computation of Brillouin zone integrals.