Research articles

Magnetic skyrmions are topological excitations that have attracted great attention recently for their potential applications in low power, ultrahigh density memory. A major challenge has been to find materials that meet the dual requirement of small skyrmions stable at room temperature. Here, the authors further both these goals by developing epitaxial FeGe films with excess Fe using atomic layer molecular beam epitaxy far from thermal equilibrium.

The condensed-matter counterpart of the Poincaré group may consist of various spacetime symmetry groups of spacetime crystals. In this work, the authors report the theoretical foundation of the projective spacetime symmetry algebras, explicitly work them out in (1,1) dimensions and discuss their consequences over spacetime lattices with gauge fluxes.

The potential for discovery with ultrafast gas-phase diffraction experiments is limited as we often rely on advanced simulations to interpret results. The authors present a method that can expand this discovery potential by directly inverting diffraction patterns for approximate molecular structure probability distributions with a ~100X real-space resolution improvement.

The investigation of a chiral active fluid composed of a carpet of standing and spinning colloidal rods, combined with simulations for synchronously rotating hard discs in a hydrodynamic explicit solvent reveals here the simultaneous occurrence and relation of two seemingly separate phenomena: active turbulence and odd viscosity.

Doping is a tried and tested method to tune the properties of a range of quantum materials either by introducing defects into the system or engineering the charge carrier concentration. Here, the authors use photoemission spectroscopy to investigate the effects of surface doping of alkali metals on the Mott insulator Ca₂RuO₄, revealing an orbital-selective surface metal-insulator transition induced by the surface-dopant interaction.

The authors experimentally demonstrate with a transmission electron microscope that single-shot 3D imaging is possible in the near-field limit, by simultaneously inferring local depth and thickness. The proposed reconstruction method uses priors from the homogenously amorphous specimen, and it can be extended for imaging multi-layered samples.

Designing quantum batteries able to outperform the classical ones requires a balance of fast charging, durable storage and effective work extraction. With their theoretical model, the authors propose a quantum battery with quadratic driving which induces plentiful useful work near to certain critical points. The model may be realized with parametric cavities or nonlinear circuits.

The nuclear decay of 176Lu can be looked at as a cosmochronometer to measure the age of astrophysical and geological events. The authors report the half-life of the 176Lu decaying to 176Hf using a method almost independent on the uncertainties in the previous experiments and the assumption for the isochron methods, in the process reconciliating the difference of measurements from previous experiments.

Many challenging problems in science and engineering rely on the study of dynamical systems that evolve continuously in time, and yet this feature proves difficult to be captured reliably using modern machine learning (ML) models. This paper develops a convergence test based on numerical analysis and illustrates how this methodology can be combined with existing ML techniques to validate models for science and engineering applications.

Here, the authors show that when non-collinear antiferromagnet Mn₃Sn is pumped by femtosecond laser pulses it acts as a source of picosecond current pulses that emit electro-dipole radiation in the THz range of the spectrum. The origin of these photo-currents are attributed to the photon drag effect.

Recently, the study of optical frequency combs and nonlinear dynamics in optical microresonators demonstrated a vast variety of dissipative structures with a wide range of nonlinear phenomena. In this paper, the authors extend the conventional systems to the chains of resonators, demonstrating rich two-dimensional dynamics in different dynamical regimes.

Quiet points (QPs) in chip-integrated microcomb platforms allow the cancellation of transduction noise arising due to the presence of Raman self-frequency shifts, but the conditions to exploit them are fortuitous and system-dependent. The authors propose a strategy to deterministically engineer QPs both in terms of spectral width and position.

Recent observations of macroscopic quantum condensation using electron-hole (e-h) bilayers have activated the research of its application to electronics. The authors propose and demonstrate a method for the formation of a self-organized bilayer at the Si MOS interface with an e-h distance of the order of the exciton Bohr radius, which paves the way for condensation and, ultimately, low-power cryogenic Si MOS devices.

While Phillips’ theory states that the early stages of wind-wave generation are governed by a resonance mechanism, the majority of studies focussed on the situation where surface waves have already been generated by the wind. The authors fill this gap and address the problem of surface wave generation when calm water is exposed to turbulent wind.

The hierarchical equations of motion approach is useful for the non-perturbative study of complex open quantum systems, which are simultaneously coupled to both bosonic and fermionic environments. To tackle these systems, the authors introduce an open-source software package (HierarchicalEOM.jl), characterized by a notable speed and accessibility to new users.

The properties of cognitive microswimmers in fluids are determined by their capability to sense a target, process information, and adapt the motion, and by hydrodynamic interactions. To gain insight on this process, the authors investigate pursuer-target pairs, for pursuers with implicitly sensing, and self-steering with limited maneuverability.

The dynamic network biomarker/marker (DNB) method is popular to detect critical points from measured data, but a unified criterion to select the most appropriate DNB is still lacking. The authors propose a giant-componentbased DNB method that directly selects the largest DNB as transition core, reflecting the progress of the transition.

The description of open systems featuring anti parity-time symmetry builds on the assumption that the system does not retain memory. Here, the authors propose a system with anti-PT-symmetry where a single time-delay encodes the retention of memory, and experimentally demonstrate it by coupling two time-delay semiconductor lasers.

Coulomb Explosion imaging is a promising technique to study the ultrafast nuclear dynamics which underpin molecular photochemistry. By initiating Coulomb explosion through soft X-ray ionization, the authors are able to image ultrafast nuclear dynamics of a prototypical photoreaction.

Superconductors with odd-parity Cooper pairs are rare and their experimental confirmation is significantly challenging. In the CeRh2As2 superconductor, the authors’ investigation reveals that the presence of competing pairings with opposite parities gives rise to a unique collective mode, which can be observed through the optical response.