We theoretically investigate nonequilibrium spin fluctuations in a ferromagnet induced by a light pulse. Using a Lindblad equation consistent with the Landau-Lifshitz-Gilbert equation, we compute the autocorrelation function of magnetization. Our analysis reveals that this function comprises both thermal and nonequilibrium components. To examine the latter in detail, we introduce a Fano factor similar to nonequilibrium current noise in electronic circuits. We demonstrate that this factor encapsulates insights into the transfer of spin units to the environment. Our findings lay the groundwork for nonequilibrium spin noise spectroscopy, offering valuable insights into spin relaxation dynamics.

Quasicrystals are materials that exhibit long-range order without translational periodicity. In soft matter, the most commonly observed quasicrystal has 12-fold symmetry and consists of tilings made out of squares and triangles. Intriguingly, both in experiments and simulations, these tilings nearly always appear with many point defects. These defects can be decomposed into squares, triangles, and an additional tile: a rhombus. In this Letter, we explore how rhombus tiles change the entropy of square-triangle 12-fold quasicrystals. We introduce a novel lattice-based Monte Carlo simulation method that uses open boundaries to allow the concentration of different tile types to fluctuate. Our simulations show that rhombus tiles significantly increase the configurational entropy of the quasicrystal phase, enhancing its stability. These findings highlight the critical role of defects in stabilizing soft-matter quasicrystals.

In practice, qubit reset must be operated in an extremely short time, which incurs a thermodynamic cost within multiple orders of magnitude above the Landauer bound. We present a general framework to determine the minimal thermodynamic cost and the corresponding optimal protocol for memory erasure under arbitrary erasure speeds. Our study reveals the divergent behavior of minimal entropy production in the short-time limit depends on the convergence and divergence of the jump operator. There is an inherent trade-off between the minimal required time and the set error probability for the convergent class. Moreover, we find the optimal protocol exhibits general features in the fast-driving regime. To illustrate these findings, we employ fermionic and bosonic baths as examples. Our results suggest that the super-Ohmic bosonic heat bath is suitable for qubit reset.

We study the quantum dynamics of an interior planar anti–de Sitter black hole, requiring unitarity in the natural time coordinate conjugate to the cosmological “constant of motion” appearing in unimodular gravity. Both the classical singularity and the horizon are replaced by a nonsingular highly quantum region; semiclassical notions of spacetime evolution are only valid in an intermediate region. For the singularity, our results should be applicable to general black holes: unitarity in unimodular time always implies singularity resolution.

We initiate the study of the interplay between T duality and classical stress tensor deformations in two-dimensional sigma models. We first show that a general Abelian T duality commutes with the $T\overline{T}$ deformation, which can be engineered by a gravitational dressing. Then, by using an auxiliary field formulation of stress tensor deformations of the principal chiral model (PCM), we prove that non-Abelian T duality and arbitrary $T\overline{T}$-like flows also commute for theories in this class. We argue that all such auxiliary field deformations of both the PCM and its T dual are classically integrable.

We predict a near-threshold (“zero energy”) peak in multiphoton ionization for a dynamical regime where the photon frequency is large compared to the binding energy of the electron. The peak position does not depend on the laser frequency but on the binding energy and the pulse duration. The effect originates from the fact that bound-continuum dipole transitions are stronger than continuum-continuum ones. To clearly observe this zero-energy photoelectric effect, the spectral width of the laser pulse should be comparable to the binding energy of the ionized orbital, and the second ionization potential should be larger than the photon energy. This suggests negative ions as ideal candidates for corresponding experiments.

Interfacial energy dissipation during stick-slip motion of a liquid drop on a nonconductive polymer substrate is shown to lead to an irreversible increase in electrical charge. This previously unobserved phenomenon occurs during surface wetting, in contrast to the previously reported charge separation mechanism that occurs during dewetting. Understanding this electrification mechanism will facilitate the design of energy harvesters and aid the development of risk mitigation strategies for electrostatic buildup in liquid flow across a wide range of industrial applications.

The dynamics of drop impact on a rigid surface strongly depends on the droplet’s velocity, its size, and its material properties. The main characteristics are the droplet’s force exerted on the surface and its maximal spreading radius. The crucial question is how do they depend on the (dimensionless) control parameters, which are the Weber number $We$ (nondimensionalized kinetic energy) and the Ohnesorge number $Oh$ (dimensionless viscosity). Here, we perform direct numerical simulations over the huge parameter range $1\le We\le {10}^3$ and ${10}^{-3}\le Oh\le {10}^2$ and in particular develop a unifying theoretical approach, which is inspired by the Grossmann-Lohse theory for wall-bounded turbulence [Grossmann and Lohse, J. Fluid Mech. 407, 27 (2000); Phys. Rev. Lett. 86, 3316 (2001)]. The key idea is to split the energy dissipation rate into the different phases of the impact process, in which different physical mechanisms dominate. The theory can consistently and quantitatively account for the $We$ and $Oh$ dependences of the maximal impact force and the maximal spreading diameter over the huge parameter space. It also clarifies why viscous dissipation plays a significant role during impact, even for low-viscosity droplets (low $Oh$), in contrast to what had been assumed in some prior theories.

The class of two-dimensional carbides and nitrides known as MXenes exhibit remarkable electronic properties. Tailoring these properties, however, requires an in-depth understanding of the band structure and Fermi-surface topology. Surface oxidation of MXenes has previously hampered the characterization of their Fermi surface, which is crucial for understanding the topology and anisotropy in the electronic structure and, ultimately, for tailoring electronic properties. Here, we reveal the Fermi surface topology and band structure of purely oxygen-terminated ${\mathrm{Ti}}_3{\mathrm{C}}_2{\mathrm{T}}_{\mathrm{x}}$ MXene achieved through rigorous thin film sample preparation and ultrahigh vacuum annealing. Polarized synchrotron radiation-based angle-resolved photoemission spectroscopy reveals electron pockets, bulk band gaps, and a Dirac-like feature in the anisotropic electronic band structure. This paves the way for a fundamental understanding of band engineering of electronic transport properties, providing insights of importance for energy storage devices, transparent conductors, and catalysis.

We demonstrate that the anomalous ionization rate observed in the Central Molecular Zone can be attributed to MeV dark matter annihilations into $e^{+}{e}^{-}$ pairs for galactic dark matter profiles with slopes $\gamma >1$. The low annihilation cross sections required avoid cosmological constraints and imply no detectable inverse Compton, bremsstrahlung, or synchrotron emission in radio, x- and $\gamma$ rays. The possible connection with the source of the unexplained 511 keV line emission in the Galactic Center suggests that both observations could be correlated and have a common origin.

The collective Auger decay (CAD) of ${\mathrm{Xe}}^{2+}4d^{-2}$ double core-hole states in which two outer-shell electrons fill the double inner-shell vacancies while releasing a third energetic Auger electron is explored using multi-electron-ion coincidence spectroscopy. The CAD branching ratio relative to the total Auger emission of ${\mathrm{Xe}}^{2+}4d^{-2}$ states is estimated to be $2\times {10}^{-2}\pm 1\times {10}^{-2}$, surpassing the branching ratios of previously reported CAD paths by a factor of 10 or more. This amplified CAD in ${\mathrm{Xe}}^{2+}4d^{-2}$ states is primarily attributable to their near-degeneracy with intermediate configurations required to promote CAD in second-order perturbation theory. Such near degeneracy is characteristic of all double inner-shell vacancy states in medium and heavy elements, suggesting that CAD paths play a more pivotal role in the relaxation of core-excited matter than is currently understood.

Rayleigh-Bénard convection is investigated with sulfur hexafluoride (${\mathrm{SF}}_6$) in the vicinity of its critical point. In the supercritical domain, direct measurements of the heat flux $Q$ as a function of the temperature difference $\mathrm{\Delta }T$ are consistent with the usual scaling laws of single-phase turbulent convection. Along the liquid-vapor coexistence curve, heat fluxes are dramatically enhanced by condensation and boiling. Optical measurements are performed to document the size and velocity of the bubbles. We report $Q(\mathrm{\Delta }T,\epsilon )$ in both domains, with $\epsilon$ the dimensionless distance to the critical point. Critical scaling laws are observed that can guide the development of theoretical models. In addition, this documents a system of diverging heat transfer coefficient, i.e., in which a significant heat flux can be achieved with an arbitrarily small temperature difference as $\epsilon \to 0$.

Recent angle-resolved photoemission spectroscopy (ARPES) experiments on the kagome metal ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ revealed distinct multimodal dispersion kinks and nodeless superconducting gaps across multiple electron bands. The prominent photoemission kinks suggest a definitive coupling between electrons and certain collective modes, yet the precise nature of this interaction and its connection to superconductivity remain to be established. Here, employing the state-of-the-art ab initio many-body perturbation theory computation, we present direct evidence that electron-phonon ($e$-ph) coupling induces the multimodal photoemission kinks in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$, and profoundly, drives the nodeless $s$-wave superconductivity, showcasing the diverse manifestations of the $e$-ph coupling. Our calculations well capture the experimentally measured kinks and their fine structures, and reveal that vibrations from different atomic species dictate the multimodal behavior. Results from anisotropic $GW$-Eliashberg equations predict a phonon-mediated superconductivity with nodeless $s$-wave gaps, in excellent agreement with various ARPES and scanning tunneling spectroscopy measurements. Despite the universal origin of the $e$-ph coupling, the contributions of several characteristic phonon vibrations vary in different phenomena, highlighting a versatile role of $e$-ph coupling in shaping the low-energy excitations of kagome metals.

The Jacob’s ladder of density functional theory (DFT) proposes the compelling view that by extending the form of successful approximations—being guided by exact conditions and selected (least empirical) norms—upper rungs will do better than the lower, thus allowing to balance accuracy and computational effort. Meta-generalized gradient approximations (MGGAs) belong to the last rung of the semilocal approximations before hybridization with nonlocal wave function theories. Among the MGGAs, the strongly constrained and appropriately normed approximation (SCAN) greatly improves upon GGAs from the lower rung. But the over magnetized solutions of SCAN make GGAs more reliable for magnetism. Here, we provide a solution that satisfies the most pressing desiderata for a density functional approximations for ferromagnetic, antiferromagnetic and noncollinear states. The approach is available in an implementation in the crystal electronic structure package.