By the complementary combination of NMR and neutron diffraction measurements, and a symmetry analysis using the previously reported magnetization measurements, a negative-chirality $\mathbf{q}$=0 magnetic structure is successfully identified as the ground state of CdCu${}_3$(OH)${}_6$(NO${}_3{)}_2\cdot$H${}_2$O, the $S$=½ perfect kagome antiferromagnet. Detailed investigation of the internal fields leads the authors to suggest a spin-locked magnetic structure with $<$100$>$ anisotropy, which is stabilized by the Dzyaloshinskii-Moriya interaction and the interactions slightly modified by the orientational order of the NO${}_3$ units.

The authors use optical excitation as a way to alter the magnetic free energy landscape and the resulting phase diagram of the frustrated honeycomb magnet $\alpha$-RuCl${}_3$. They time-track experimentally the magneto-optical response from the $\alpha$-RuCl${}_3$’s zigzag-ordered ground state after photoexcitation and they reproduce the observed dynamics within a Ginzburg-Landau model. A quasistationary spin disordered state is induced above a critical photoexcitation density, suggesting a new route to reach a nontrivial spin disordered state in Kitaev-like magnets such as $\alpha$-RuCl${}_3$.

One secret to the charm of two-dimensional (2D) van der Waals materials is that their interlayer coupling lies in a sweet spot: weak enough to render the individual layers electronically quasi-2D, yet strong enough to produce distinct behavior upon stacking individual layers. Here, the authors utilize soft-x-ray angle-resolved photoemission spectroscopy to extract the interlayer hopping parameters in the typical transition metal dichalcogenide 2$H$-NbS${}_2$. Comparison with first-principles calculations reveals the influence of atomic distances and hybrid functionals on interlayer coupling.

Integer quantum Hall states and their generalization to topological insulators and superconductors are paradigmatic examples of invertible fermionic topological states of matter. Here, the authors develop a comprehensive characterization and classification of invertible fermionic topological phases of matter in two spatial dimensions for general symmetry groups. The results are nonperturbative and apply to strongly interacting systems. In particular, they extend previous classification results to account for the possible chiral nature of invertible phases.

Entanglement is a key tool to classify quantum phases of matter in and out of equilibrium. Here, the authors introduce a phenomenological quasiparticle picture for entanglement dynamics in monitored systems evolving under the effect of quantum jumps. Within this picture, entanglement is carried by non-Hermitian quasiparticles, associated to the no-click limit of the measurement protocol, that propagate ballistically and are randomly reset with a rate given by their inverse lifetime. The authors show how this picture qualitatively reproduces the entanglement transition in the monitored Ising chain.

The topological phase transition introduced by Kosterlitz and Thouless has become a central concept in condensed matter physics. With the increasing relevance of topological phases to applications in spintronics, it is important to extend the description of the Kosterlitz-Thouless transition in an infinite, isotropic two-dimensional XY ferromagnet to experimentally realizable systems such as a finite, anisotropic ultrathin film with fourfold in-plane anisotropy. Using a renormalization group analysis, this description is used to calculate the magnetic susceptibility for comparison to experiment.

The authors mix fluctuations of different origin to obtain pairing in the odd-frequency spin-triplet channel. Such fluctuations are enhanced in disordered two-dimensional systems, and the pairing is predicted to be sufficient for the instability in the odd-frequency spin-triplet channel.

Spin-orbit interaction in a crystal surface typically causes helical spin polarization, namely topological or Rashba states. The authors have noticed that the known cases of such surface spin polarization are limited to ideal models because of the symmetry operations in the surface atomic structure. Here, they reveal numerous hidden surface spin textures in a surface quasi-1D system, which vary from ferromagnetic to antiferromagnetic depending on the wave vector, with a small number of symmetry operations. This achievement suggests that versatile spin texture at the surface would be tailored by tuning the symmetry operations.

Conditional probability density functional theory (CP-DFT) determines the ground-state energy of a many-electron system by finding the conditional probability density from a parallelizable series of Kohn-Sham DFT calculations. By directly calculating conditional probability densities, the authors bypass the need for an approximate exchange-correlation (XC) energy functional. CP-DFT is formally exact, but approximate potentials are used in practice. We explore a suitable approximation that satisfies many presented exact constraints and even properly dissociates neutral hydrogen chains.

The numerical renormalization group is the gold standard for solving quantum impurity models. To compute the self-energy, one routinely employs an equation of motion instead of inverting Dyson’s equation. Still, in challenging regimes, the results often suffer from artifacts. The author shows here that a new estimator, derived by a twofold application of the equation of motion, yields greatly improved results, as key aspects of the retarded self-energy require only the imaginary parts of auxiliary correlators and not their real parts obtained by a Kramers-Kronig transform.

It is known that if the dipolar interaction is ignored or replaced by an effective magnetic anisotropy, the theoretical computations predict that a domain wall is transparent to spin waves. Taking into account the full complexity of this interaction, the authors show that the domain wall does indeed reflect spin waves. The scattering parameters are computed by treating the dipolar interaction perturbatively in the Born approximation, which is not straightforward due to the nonlocality of this interaction. A lateral shift of the scattered waves is also predicted.

The ability to initialize excitonic states in the high-energy orbital levels of quantum dots provides additional degrees of freedom for all-optical spin-driving protocols. Here, the authors show that unconventional two-photon excitation can simultaneously photocreate two electron-hole pairs located on distinct orbital levels of a GaAs quantum dot. Tuning the laser energy allows the triplet and singlet spin states of the biexciton to be selectively addressed. The measured radiative cascades suggest the importance of many-body effects in these weakly confined dots.

A general theory of bound states in the continuum (BICs) in multipolar lattices composed of Mie-resonant or plasmonic nanoparticles is developed. It is revealed that the BICs, which are usually very sensitive to parameters of the photonic structure, can be completely robust, remaining pinned to specific directions in $k$ space. The developed approach sets a direct relation between the topological charge of BIC and the asymptotic behavior of its $Q$ factor that is important for engineering the photonic structures supporting BICs.

Structurally similar transition metal systems can exhibit very different magnetic properties. An instructive example is the widely studied Pd/Fe/Ir(111) multilayer, which shows a spin-spiral ground state, while Pd/Co/Ir(111) presents a ferromagnetic (single-domain) ground state. Here, the authors analyze the origin of this difference combining $ab$ $initio$ and atomistic spin-dynamics calculations, demonstrating that the distinct behaviors can be explained by a simple rigid-band-like model. This analysis highlights the possibility of tuning topological magnetic structures by alloying and/or external agents, e.g., electric fields.

The Newman-Moore model on the 2D triangular lattice is a classic example of a statistical mechanical model with immobile fractal excitations: fractons. These result in kinetic constraints leading to glassy behavior. Here, the authors generalize this construction to two 3D lattices, trillium and hyperhyperkagome. While these models exhibit a similar phenomenology, the authors show that the underlying fractons have a richer structure and are intimately connected to the matrix cellular automata that describe the manifold of ground states.