We propose the jet charge observable as a novel probe of flavor structure in the nucleon spin program at the electron ion collider (EIC) and develop the underlying framework from first principles. We show that jet charge measurements can substantially enhance the sensitivity of spin asymmetries to different partonic flavors in the nucleon. This sensitivity can be further improved by constructing the jet charge using only a subset of hadron species (pions or kaons) in the jet. As an example, we use the Sivers asymmetry in back-to-back electron-jet production at the EIC to show that the jet charge can be a unique tool in constraining the Sivers function for different partonic flavors.

We demonstrate a widely applicable technique to absolutely calibrate the energy scale of x-ray spectra with experimentally well-known and accurately calculable transitions of highly charged ions, allowing us to measure the $K$-shell Rydberg spectrum of molecular ${\mathrm{O}}_2$ with 8 meV uncertainty. We reveal a systematic $\sim 450\mathrm{meV}$ shift from previous literature values, and settle an extraordinary discrepancy between astrophysical and laboratory measurements of neutral atomic oxygen, the latter being calibrated against the aforementioned ${\mathrm{O}}_2$ literature values. Because of the widespread use of such, now deprecated, references, our method impacts on many branches of x-ray absorption spectroscopy. Moreover, it potentially reduces absolute uncertainties there to below the meV level.

The development of useful photon-photon interactions can trigger numerous breakthroughs in quantum information science, however, this has remained a considerable challenge spanning several decades. Here, we demonstrate the first room-temperature implementation of large phase shifts ($\approx \pi$) on a single-photon level probe pulse ($1.5\mu \mathrm{s}$) triggered by a simultaneously propagating few-photon-level signal field. This process is mediated by ${\text{Rb}}^{87}$ vapor in a double-$\mathrm{\Lambda }$ atomic configuration. We use homodyne tomography to obtain the quadrature statistics of the phase-shifted quantum fields and perform maximum-likelihood estimation to reconstruct their quantum state in the Fock state basis. For the probe field, we have observed input-output fidelities higher than 90% for phase-shifted output states, and high overlap (over 90%) with a theoretically perfect coherent state. Our noise-free, four-wave-mixing-mediated photon-photon interface is a key milestone toward developing quantum logic and nondemolition photon detection using schemes such as coherent photon conversion.

Theoretical studies on wave turbulence predict that a purely classical system of random waves can exhibit a process of condensation, which originates in the singularity of the Rayleigh-Jeans equilibrium distribution. We report the experimental observation of the transition to condensation of classical optical waves propagating in a multimode fiber, i.e., in a conservative Hamiltonian system without thermal heat bath. In contrast to conventional self-organization processes featured by the nonequilibrium formation of nonlinear coherent structures (solitons, vortices,…), here the self-organization originates in the equilibrium Rayleigh-Jeans statistics of classical waves. The experimental results show that the chemical potential reaches the lowest energy level at the transition to condensation, which leads to the macroscopic population of the fundamental mode of the optical fiber. The near-field and far-field measurements of the condensate fraction across the transition to condensation are in quantitative agreement with the Rayleigh-Jeans theory. The thermodynamics of classical wave condensation reveals that the heat capacity takes a constant value in the condensed state and tends to vanish above the transition in the normal state. Our experiments provide the first demonstration of a coherent phenomenon of self-organization that is exclusively driven by optical thermalization toward the Rayleigh-Jeans equilibrium.

We study two-component (or pseudospin-$1/2$) bosons with pair hopping interactions in synthetic dimension, for which a feasible experimental scheme on a square optical lattice is also presented. Previous studies have shown that two-component bosons with on-site interspecies interaction can only generate nontrivial interspecies paired superfluid (super-counter-fluidity or pair-superfluid) states. In contrast, apart from interspecies paired superfluid, we reveal two new phases by considering this additional pair hopping interaction. These novel phases are intraspecies paired superfluid (molecular superfluid) and an exotic noninteger Mott insulator which shows a noninteger atom number at each site for each species, but an integer for total atom number.

Using bilayer ${\mathrm{CrI}}_3$ as an example, we demonstrate that stacking domain walls in van der Waals magnets can host one-dimensional (1D) magnon channels, which have lower energies than bulk magnons. Interestingly, some magnon channels are hidden in magnetically homogeneous background and can only be inferred with the knowledge of stacking domain walls. Compared to 1D magnons confined in magnetic domain walls, 1D magnons in stacking domain walls are more stable against external perturbations. We show that the relaxed moiré superlattices of small-angle twisted bilayer ${\mathrm{CrI}}_3$ is a natural realization of stacking domain walls and host interconnected moiré magnon network. Our Letter reveals the importance of stacking domain walls in understanding magnetic properties of van der Waals magnets and extends the scope of stacking engineering to magnetic dynamics.

Based on the first-principles prediction, we report the magnetoelectric coupling effect in two-dimensional multiferroic bilayer ${\mathrm{VS}}_2$. The ground-state $3R$-type stacking breaks space inversion symmetry, therefore introducing a spontaneous polarization perpendicular to the layer plane. We further reveal that the out-of-plane ferroelectric polarization of bilayer ${\mathrm{VS}}_2$ can be reversed upon interlayer sliding of an in-plane translation. Each ${\mathrm{VS}}_2$ layer has a ferromagnetic state with an opposite magnetic moment between two antiferromagnetically ordered layers. We found that ferroelectricity and antiferromagnetism can be coupled together by a ferrovalley in bilayer ${\mathrm{VS}}_2$ to realize electronic control of magnetism. Remarkably, a net magnetic moment is generated by reducing the interlayer distance, and an electric field is able to achieve linear and second-order nonlinear magnetoelectric coupling in bilayer ${\mathrm{VS}}_2$.

We investigate the role of the effective range on the bulk viscosity of $s$- and $p$-wave Fermi gases. At resonance, the presence of the effective range breaks the scale invariance of the system, and hence results in a nonzero bulk viscosity. However, we show that the effective range plays a very different role in the two cases. In the $s$-wave case, the role of the effective range is perturbative, and its contribution to the bulk viscosity vanishes in the limit of zero effective range. On the other hand, the effective range in $p$-wave Fermi gases leads to a nonzero bulk viscosity, even in the zero-range limit. We employ a general diagrammatic approach to compute the bulk viscosity spectral function that includes the effects of the effective range. We then compute the analytic expressions for the spectral function in the high temperature limit, at low and high frequencies. We also derive the sum rules for the bulk viscosity spectral function for both $s$- and $p$-wave gases.

We theoretically propose and experimentally demonstrate the use of motional sidebands in a trapped ensemble of ${}^{87}\mathrm{Rb}$ atoms to engineer tunable long-range $XXZ$ spin models. We benchmark our simulator by probing a ferromagnetic to paramagnetic dynamical phase transition in the Lipkin-Meshkov-Glick model, a collective $XXZ$ model plus additional transverse and longitudinal fields, via Rabi spectroscopy. We experimentally reconstruct the boundary between the dynamical phases, which is in good agreement with mean-field theoretical predictions. Our work introduces new possibilities in quantum simulation of anisotropic spin-spin interactions and quantum metrology enhanced by many-body entanglement.

Motivated by the possible presence of deconfined quark matter in neutron stars and their mergers and the important role of transport phenomena in these systems, we perform the first-ever systematic study of different viscosities and conductivities of dense quark matter using the gauge/gravity duality. Using the V-QCD model, we arrive at results that are in qualitative disagreement with the predictions of perturbation theory, which highlights the differing transport properties of the system at weak and strong coupling and calls for caution in the use of the perturbative results in neutron star applications.

The only anticipated resonant contributions to $B^{+}\to D^{+}{D}^{-}{K}^{+}$ decays are charmonium states in the $D^{+}{D}^{-}$ channel. A model-independent analysis, using LHCb proton-proton collision data taken at center-of-mass energies of $\sqrt{s}=7$, 8, and 13 TeV, corresponding to a total integrated luminosity of $9{\mathrm{fb}}^{-1}$, is carried out to test this hypothesis. The description of the data assuming that resonances only manifest in decays to the $D^{+}{D}^{-}$ pair is shown to be incomplete. This constitutes evidence for a new contribution to the decay, potentially one or more new charm-strange resonances in the $D^{-}{K}^{+}$ channel with masses around $2.9\mathrm{GeV}/c^2$.

We show how state-dependent optical potentials can be used to trap a pair of molecules in different internal states at a separation much smaller than the wavelength of the trapping light. This close spacing greatly enhances the dipole-dipole interaction and we show how it can be used to implement two-qubit gates between molecules that are 100 times faster than existing protocols and than rotational coherence times already demonstrated. We analyze complications due to hyperfine structure, tensor light shifts, photon scattering, and collisional loss, and conclude that none is a barrier to implementing the scheme.

We study three-atom inelastic scattering in ultracold ${}^{39}\mathrm{K}$ near a Feshbach resonance of intermediate coupling strength. The nonuniversal character of such resonance leads to an abnormally large Efimov absolute length scale and a relatively small effective range $r_e$, allowing the features of the ${}^{39}\mathrm{K}$ Efimov spectrum to be better isolated from the short-range physics. Meticulous characterization of and correction for finite-temperature effects ensure high accuracy on the measurements of these features at large-magnitude scattering lengths. For a single Feshbach resonance, we unambiguously locate four distinct features in the Efimov structure. Three of these features form ratios that obey the Efimov universal scaling to within 10%, while the fourth feature, occurring at a value of scattering length closest to $r_e$, instead deviates from the universal value.

The photoluminescence (PL) characterization spectrum has been widely used to study the electronic energy levels. ${\mathrm{Ho}}^{3+}$ is one of the commonly used doping elements to provide the PL with concentration limited to 1% atomic ratio. Here, we present a tricolor PL achieved in pyrochlore ${\mathrm{Ho}}_2{\mathrm{Sn}}_2{\mathrm{O}}_7$ through pressure treatment at room temperature, which makes a non-PL material to a strong multiband PL material with ${\mathrm{Ho}}^{3+}$ at the regular lattice site with 18.2% concentration. Under a high pressure compression-decompression treatment up to 78.0 GPa, the ${\mathrm{Ho}}_2{\mathrm{Sn}}_2{\mathrm{O}}_7$ undergoes pyrochlore ($Fd3m$), to cotunnite ($Pnma$), then amorphous phase transition with different ${\mathrm{Ho}}^{3+}$ coordinations and site symmetries. The PL emerged from 31.2 GPa when the pyrochlore to cotunnite phase transition took place with the breakdown of site symmetry and enhanced hybridization of ${\mathrm{Ho}}^{3+}$ $4f$ and $5d$ orbitals. Upon decompression, the materials became an amorphous state with a partial retaining of the defected cotunnite phase, accompanied with a large enhancement of red-dominant tricolor PL from the ion pair cross-relaxation effect in the low-symmetry ($C_1$) site, in which two distinct ${\mathrm{Ho}}^{3+}$ emission centers ($S$ center and $L$ center) are present.

High-temperature superconductivity emerges in many different quantum materials, often in regions of the phase diagram where the electronic kinetic energy is comparable to the electron-electron repulsion. Describing such intermediate-coupling regimes has proven challenging as standard perturbative approaches are inapplicable. Here, we employ quantum Monte Carlo methods to solve a multiband Hubbard model that does not suffer from the sign problem and in which only repulsive interband interactions are present. In contrast to previous sign-problem-free studies, we treat magnetic, superconducting, and charge degrees of freedom on an equal footing. We find an antiferromagnetic dome accompanied by a metal-to-insulator crossover line in the intermediate-coupling regime, with a smaller superconducting dome appearing in the metallic region. Across the antiferromagnetic dome, the magnetic fluctuations change from overdamped in the metallic region to propagating in the insulating region. Our findings shed new light on the intertwining between superconductivity, magnetism, and charge correlations in quantum materials.

Bond-dependent magnetic interactions can generate exotic phases such as Kitaev spin-liquid states. Experimentally determining the values of bond-dependent interactions is a challenging but crucial problem. Here, I show that each symmetry-allowed nearest-neighbor interaction on triangular and honeycomb lattices has a distinct signature in paramagnetic neutron-diffraction data, and that such data contain sufficient information to determine the spin Hamiltonian unambiguously via unconstrained fits. Moreover, I show that bond-dependent interactions can often be extracted from powder-averaged data. These results facilitate experimental determination of spin Hamiltonians for materials that do not show conventional magnetic ordering.

The Coulomb drag effect has been observed as a tiny current induced by both electron-hole asymmetry and interactions in normal coupled quantum dot devices. In the present work we show that the effect can be boosted by replacing one of the normal electrodes by a superconducting one. Moreover, we show that at low temperatures and for sufficiently strong coupling to the superconducting lead, the Coulomb drag is dominated by Andreev processes, is robust against details of the system parameters, and can be controlled with a single gate voltage. This mechanism can be distinguished from single-particle contributions by a sign inversion of the drag current.