We report that span-wise sinusoidal wall oscillations can significantly reduce drag in wall-bounded turbulent flows laden with neutrally buoyant, finite-size spherical particles—surpassing the drag reduction observed in corresponding single-phase flows. Direct numerical simulations reveal that this enhanced drag reduction arises from a coupling mechanism between the suspended particles and the wall motion. The span-wise Stokes flow induces particle migration toward the channel center and suppresses near-wall turbulence, thereby reducing the effective viscosity. Quantitatively, we identify an approximately linear relationship linking the coupling-induced drag reduction to both the oscillation-driven variation in near-wall particle volume fraction and the influence of particle size. These findings uncover a previously unrecognized synergistic mechanism for turbulent multiphase drag reduction, bridging Einstein's viscosity model with turbulent boundary layer theory. This insight suggests a approach to actively control wall-bounded multiphase turbulence, with broad implications for fluid mechanics and complex flow systems.

Neutron diffraction is a powerful tool in the study of quantum materials and associated emergent phenomena as it allows for direct detection of magnetic structure even at ultra-low temperatures. As pressure can drive systems across quantum critical points and tune emergent behaviors at the quantum scale, coupling neutron diffraction with extreme conditions of high pressure at (ultra-)low temperatures has been a key research target over decades. This has proven challenging as magnetic neutron diffraction typically requires large sample volumes due to flux limitations, whereas high-pressure studies require small sample volumes due to pressure limitations. Combining these two contradictory requirements poses many difficulties, but also brings opportunities in research and development. Here, we address these shortcomings through the use of a diamond anvil cell equipped with polycrystalline anvils with relatively large sample volumes coupled with the high neutron flux made available by the high-pressure diffractometer of the Spallation Neutron Source. This particular diamond anvil cell configuration has previously proven useful for single-crystal samples and is here coupled with the ultra-low temperatures of a dilution refrigerator for the first time. Our study on a single crystal of ${\mathrm{Yb}}_2{\mathrm{O}}_3$ successfully collected magnetic neutron diffraction data at 5.3 GPa below 200 mK inside a dilution refrigerator. We have performed a detailed analysis of the magnetic diffraction data to investigate the magnetic structure under pressure and observed a subtle shift in the transition temperature. This development will open the door for future studies on magnetic materials with these much-desired coupled extremes of high pressure and ultra-low temperatures.

A remarkable response of a three-component hydrodynamic plasma consisting of electrons, light holes, and heavy holes to an external electric field has been discovered in a quantum well structure where the field causes counterflows of light and heavy holes: Heavy holes propagate in the direction of the electric field, while light holes move in the direction opposite to the electric field, in the same direction as the electrons. The observed effect is due to the different scattering efficiencies of electrons by light and heavy holes, which causes the Coulomb drag of light holes by electrons, while the drift in the electric field is responsible for the propagation of heavy holes. As a consequence of the Coulomb electron-hole drag, negative conductivity of light holes is observed.

We study the spin relaxation in a single-electron bilayer graphene quantum dot due to the spin-orbit coupling. The spin relaxation is assisted by the emission of acoustic phonons via the bond-length change and deformation potential mechanisms and $1/f$ charge noise. In the perpendicular magnetic-field dependence of the spin relaxation rate $T_1^{-1}$, we predict a monotonic increase of $T_1^{-1}$ at higher fields where the electron-phonon coupling via the deformation potential plays a dominant role in spin relaxation. We show a less pronounced dip in $T_1^{-1}$ at lower magnetic fields due to the competition between the electron-phonon coupling due to bond-length change and $1/f$ charge noise. Finally, detailed comparisons of the magnetic-field dependence of the spin relaxation with the existing experiments by Banszerus et al. [Nat. Commun. 13, 3637 (2022)] and Gächter et al. [PRX Quantum 3, 020343 (2022)] are reported.

Fracture networks in the subsurface often comprise multiple fracture sets, introducing anisotropy and heterogeneity due to wide variations in fracture orientations, sizes, and conductivities. In this study, we develop a finite-size scaling (FSS) hypothesis, rooted in percolation theory, to highlight the role of critical sets—those that conduct the majority of flow—in controlling the permeability of random fracture networks. Definitions of the FSS input quantities are provided, incorporating nondimensionalizations to account for the complexity of the networks, based on the statistical properties of the fracture parameters across all sets. For cases where critical sets are present, we emphasize their dominant role and propose modified definitions based solely on the parameters of these critical sets, in line with the idea that the density of critical sets determines the magnitude of permeability. FSS results demonstrate that the hypothesis serves as a universal model for characterizing anisotropic permeability in complex fracture networks, provided that the influence of critical sets is properly addressed. This finding can be extended to other complex systems where conductive objects can be categorized into distinct sets.

We explore the impact and scaling of effective interactions between two and three impurity atoms, induced by a bosonic medium, on their density distributions. To facilitate the detection of mediated interactions, we propose a setup where impurities are trapped in a tilted double-well potential, while the medium is confined to a ring. The tilt of the potential breaks the spatial inversion symmetry allowing us to exploit the population of the energetically elevated well as a probe of induced interactions. For two impurities, the interaction with the medium reduces the impurity population at the energetically elevated well, which we interpret as evidence of induced impurity-impurity attraction. Furthermore, the impact of an induced three-body interaction is unveiled by comparing the predictions of an effective three-body model with many-body simulations. We extend our study for induced interactions to a three-component mixture containing distinguishable impurities. Our results suggest pathways to detect and tune induced two- and three-body interactions.

The magnetic field fluctuations that mediate a magnetohydrodynamic turbulent cascade have distinct magnetic topologies and associated energy transfer rates. Magnetic field topology is classified by the magnetic field gradient tensor constructed from solar wind in situ observations by the four Cluster spacecraft tetrahedron on a scale of $\sim 40$ proton gyroradii. Energy transfer rates are estimated instantaneously from the third-order term. We find on average 25% and up to 60% larger forward energy transfer rates in hyperbolic topology compared to flux ropes/plasmoids. Hyperbolic topology, consistent with reconnection, preferentially contributes to the forward energy cascade in magnetohydrodynamic turbulence in the solar wind. This forward cascade is a candidate mechanism for heating the solar wind.

The (non)equivalence of canonical and microcanonical ensembles is a fundamental question in statistical physics, concerning whether the use of soft and hard constraints in the maximum-entropy construction leads to the same description of a system. Despite the fact that maximum-entropy models are also commonly used in statistical inference, pattern detection, and hypothesis testing, a complete understanding of the effects of ensemble nonequivalence on statistical modeling is still missing. Here, we study this problem from a rigorous model selection perspective by comparing canonical and microcanonical models via the minimum description length principle, which yields a trade-off between likelihood, measuring model accuracy, and complexity, measuring model flexibility and its potential to overfit data. We compute the normalized maximum likelihood (NML) of both formulations and find that (1) microcanonical models always achieve higher likelihood but are always more complex; (2) the optimal model choice depends on the empirical values of the constraints—the canonical model performs best when its fit to the observed data exceeds its uniform average fit across all realizations; (3) in the thermodynamic limit, the difference in description length per node vanishes when ensemble equivalence holds but persists otherwise, showing that nonequivalence implies extensive differences between large canonical and microcanonical models. Finally, we compare the NML approach to Bayesian methods, showing that (4) the choice of priors, practically irrelevant in equivalent models, becomes crucial when an extensive number of constraints are enforced, possibly leading to very different outcomes.

Spin models featuring infinite-range, homogeneous all-to-all interactions can be efficiently described due to the existence of a symmetry-restricted Hilbert subspace and an underlying classical phase-space structure. However, when the permutation invariance of the system is weakly broken, such as by long- but finite-range interactions, these tools become mathematically invalid. Here, we propose to approximately describe these scenarios by considering additional many-body subspaces according to the hierarchy of their coupling to the symmetric subspace, defined by leveraging the structure of irreducible representations (irreps) of the group $SU\left(2\right)$. We put forward a procedure, dubbed “irrep distillation,” which defines these additional subspaces to minimize their dimension at each order of approximation. We discuss the validity of our method in connection with the occurrence of quantum many-body scars, benchmark its utility by analyzing the dynamical and equilibrium phase transitions, outline its phenomenology, and compare its use-cases against other approximations of long-range many-body systems.

This work addresses how the growth of invariant operators is influenced by their underlying symmetry structure. For this purpose, we introduce the symmetry-resolved Krylov complexity, which captures the time evolution of each block into which an operator, invariant under a given symmetry, can be decomposed. We find that, at early times, the complexity of the full operator is equal to the average of the symmetry-resolved contributions. At later times, however, the interplay among different charge sectors becomes more intricate. In general, the symmetry-resolved Krylov complexity depends on the charge sector, although in some cases this dependence disappears, leading to a form of Krylov complexity equipartition. Our analysis lays the groundwork for a broader application of symmetry structures in the study of Krylov space complexities with implications for thermalization and universality in many-body quantum systems.

A quantum many-body scar is an eigenstate of a chaotic many-body Hamiltonian that exhibits two seemingly incongruous properties: Its energy eigenvalue corresponds to a high temperature, yet its entanglement structure resembles that of low-temperature eigenstates, such as ground states. Traditionally, a temperature is assigned to an energy eigenvalue through the textbook canonical temperature-energy relationship. However, in this work, we use the eigenstate subsystem temperature—a recently developed quantity that assigns a temperature to an energy eigenstate, based on the structure of its reduced density matrix. For a thermal state, the eigenstate subsystem temperature is approximately equal to its canonical temperature. Given that quantum many-body scars have a ground-state-like entanglement structure, it is not immediately clear that their eigenstate subsystem temperature would be close to their canonical temperature. Surprisingly, we find that this is the case: The quantum many-body scars retain local information about their position in the spectrum encoded within their state structure.

Assemblies of plasmonic nanoparticles (NPs) support hybridized modes of localized surface plasmons (LSPs), which delocalize in geometrically well-ordered arrangements. Here, the hybridization behavior of LSPs in geometrically completely disordered two-dimensional arrangements of Au NPs fabricated by an e-beam synthesis method is studied. Employing electron energy loss spectroscopy in a scanning transmission electron microscope and numerical simulations, the disorder-driven spatial and spectral localization of the coupled LSP modes that depends on the NP thickness is revealed. Below a NP thickness of 0.4 nm, localization increases toward higher hybridized LSP mode energies. In comparison, above 10 nm thickness, a decrease of localization toward higher mode energies is observed. In the intermediate thickness regime, a transition of the energy dependence of the localization between the two limiting cases, exhibiting a mode energy with minimal localization, is observed. It is shown that this behavior is mainly driven by the energy and thickness dependence of the polarizability of the individual NPs.

Electron-electron and electron-phonon interactions are responsible for the formation of spin, charge, and superconducting correlations in layered quantum materials. A paradigmatic model for such materials that captures both kinds of interactions is the two-dimensional Hubbard-Holstein model with a dispersionless Einstein phonon. In this work, we provide a detailed analysis of the magnetic, density, and superconducting fluctuations at and away from half filling. To that end, we employ the functional renormalization group using the recently introduced extension of the single-boson exchange formulation. More precisely, we go beyond previous approaches to the model by resolving the full frequency dependence of the two-particle vertex and taking into account the feedback from the electronic self-energy. We perform broad parameter scans in the space of Hubbard repulsion, electron-phonon coupling strength, and phonon frequency to explore the leading magnetic, density, and superconducting susceptibilities from the adiabatic to the anti-adiabatic regime. Our numerical data reveal that self-energy effects lead to an enhancement of the $d$-wave superconducting susceptibility toward larger phonon frequencies, in contrast to earlier isotope-effect studies. At small phonon frequencies, large density contributions to the $s$-wave superconducting susceptibility change sign and eventually lead to a reduction of $s$-wave superconductivity with increasing electron-phonon coupling, signaling the breakdown of Migdal-Eliashberg theory. We analyze our findings systematically, employing detailed diagnostics of the intertwined fluctuations and pinning down the various positive and negative isotope effects of the physical susceptibilities. Our results pave the way for a more comprehensive understanding of the interplay of electron-electron and electron-phonon interactions in correlated quantum materials.

Multimagnon bound states were predicted nearly a century ago and have since been a key topic in condensed matter physics due to their intriguing quantum properties. However, their realization in natural materials remains elusive, especially in low-dimensional quantum magnets, where stabilizing them is particularly challenging due to the traditionally required extremely high external magnetic fields near or below presently available experimentally achieved fields using pulsed techniques in spite of corresponding resolution problems. However, these difficulties may be circumvented considering the much easier and convenient experimental case of ambient external magnetic fields. Therefore, we introduce a mechanism that enables the stabilization of multimagnon bound states in quasi-one-dimensional edge-shared cuprates. Our theoretical framework, supported by numerical simulations and experimental data, demonstrates that small antiferromagnetic interchain couplings act as effective internal magnetic fields, promoting a collinear antiferromagnetic order and enabling magnon condensation even at zero external field. This intrinsic stabilization mechanism eliminates the need for high external fields, offering a platform that is more accessible for experimental realization. We validate this concept by applying it to representative materials such as ${\mathrm{Li}}_2{\mathrm{CuO}}_2, {\mathrm{Ca}}_2{\mathrm{Y}}_2\mathrm{Cu}{}_5{\mathrm{O}}_{10}, {\mathrm{LiCuSbO}}_4$, and ${\mathrm{PbCuSO}}_4$(${\mathrm{OH})}_2$. Beyond its experimental feasibility, this mechanism could drive advancements in magnon-based quantum computing, low-power spintronic devices, and high-speed magnonic circuits. Moreover, our findings reveal that small interchain and/or interlayer couplings can generally unlock previously overlooked magnetic phenomena, redefining the nature of magnetically ordered states and expanding the frontiers of quantum magnetism.

We introduce a method for cooling atoms in an optical dipole trap using pulse-width modulation (PWM) technique, without reducing the laser power of the dipole trap. The PWM technique involves digital modulation of the trap at a fixed frequency. The effective time-averaged dipole potential is lowered by adjusting the duty cycle of the modulation, thereby implementing evaporative cooling. We show that this technique effectively reduces temperature and enhances phase space density. A comparison with the standard method of evaporative cooling has also been made. Apart from the atom loss due to reduction of the effective trapping potential, we observe an additional loss channel originating from the lack of trapping potential during the trap “off” time. This atom loss is observed at different modulation frequencies which are an order of magnitude higher compared to trapping frequency of dipole trap. The PWM technique provides an alternative to traditional evaporative cooling in scenarios where it is preferred that the laser power of the trap should be constant.

We present an approach for free-electron-driven optical vortex emission through interaction with the quasi-bound states in the continuum (quasi-BICs). Based on a unified framework for free electron-nanophotonic interaction and time domain simulations, we show that the free electron beam can efficiently excite the quasi-BIC under the phase-matching condition. The intrinsic $k$-space polarization anisotropy associated with the quasi-BIC imprints a geometric phase onto the emission, and thus generates an intrinsic optical vortex. We then reveal a link between the topological charge of the quasi-BIC and the emitted optical vortex by analyzing the far-field polarization structure and phase distribution. This mechanism offers a promising approach to creating nanoscale electron-beam-driven structured light sources without the need for complex chiral nanostructures, thereby advancing the interdisciplinary study of free-electron optics and nanophotonics.