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Despite exhibiting ferroelectric features, SrTiO₃ fails to display long-range polar order at low temperatures due to quantum fluctuations. An ultrafast X-ray diffraction experiment now probes polar dynamics of this material at the nanometre scale.

The axial Higgs mode is theoretically attributed to a hidden ferroaxial component of charge order. In rare-earth tritellurides, this ferroaxial order is now shown to be induced by intertwined orbital and charge orders.

Rare earth Nickelates, (RENiO₃) host a bond disproportionation phase transition where oxygen 2p holes form at one of the Ni sites. This process results in a spin-disproportionation state where a singlet state is formed by the spin of the nickel and the spin of the oxygen hole at every other site. Here, Li et al find evidence of this spin-disproportionated state in a rareearth nickelate.

Single crystals of organolead halide perovskites exhibit large carrier mobilities and long diffusion lengths. Here, the authors succeed in growing the single crystals on planar substrates and integrate them as the active layer of visible photodetectors with a large gain-bandwidth product.

CrSBr, a van der Waals antiferromagnetic semiconductor, is used to fabricate photonic crystal slabs, featuring exceptional in situ control over optical behaviour and thus enabling precise manipulation of photonic modes at near-visible and infrared wavelengths.

Experimental observations and theoretical analysis provide evidence that the spin polarization of the spin-spiral type II multiferroic NiI₂ exhibits p-wave magnetism and its spin chirality is related to ferroelectric polarization, which can be electrically controlled. 

Here, Pelliciari et al. present resonant inelastic X-ray scattering on monolayer samples of unconventional superconductor FeSe, finding evidence for gapped and dispersionless spin excitations. These experiments are very difficult due to the extremely small scattering volume of the FeSe monolayer.

Experiments that directly probe the quantum geometric tensor in solids have not been reported. Now, the quantum metric and spin Berry curvature—dual components of the quantum geometric tensor—have been simultaneously measured in reciprocal space.

Embedding quantum dots in a perovskite matrix yields efficient light emitters.

Nickelates have been shown to host unconventional superconductivity, and recently it has been found that the choice of substrate can significantly change the superconducting critical temperature. This suggests, that like some Cuprates, strain could be important. Here Gao, Fan, Wang, and coauthors find that magnetic excitations in a parent Nickelate are insensitive to substrate choice, and therefore strain, which differs markedly from the case of Cuprates.

Hydrostatic pressure is an underexplored tuning knob to study moiré systems. Here a MoS₂/WSe₂ heterostructure is compressed and the enhancement in the moiré potential strength is quantified via moiré-activated Raman modes.

Electrons in f orbitals can create localized states that interact strongly and drive strange metal and critical behaviour via the Kondo mechanism. Now a mechanism of geometric frustration enables similar phenomena with d electrons.

Angle-resolved photoemission spectroscopy of CaNi₂ shows a band with vanishing dispersion across the full 3D Brillouin zone that is identified with the pyrochlore flat band as well as two additional flat bands that arise from multi-orbital interference of Ni d-electrons.

Strongly correlated electron systems, such as the chromates, can exhibit a range of unique electronic configurations, the phase diagram of which can become even richer when considering non-equilibrium properties. Here, the authors apply ultrafast optical spectroscopy to α-Sr₂CrO₄ in order to investigate its spin and orbital ordering dynamics and the changes that occur when varying the pump photon energy.

FeSe does not exhibit magnetic order and lacks a nematic quantum critical point coinciding with optimal superconductivity, suggesting that an orbital mechanism drives nematicity, but direct evidence is lacking. Here, combining X-ray linear dichroism with in situ uniaxial stress, the role of spontaneous orbital polarization in nematic-phase FeSe is determined.

A prototypical kagome metal with magnetic and topological properties is identified.

The authors use high-resolution angle-resolved photoemission spectroscopy to determine the microscopic structure of three-dimensional charge order in AV₃Sb₅ (A = K, Rb, Cs) and its interplay with superconductivity.

Metal halide perovskites are promising for solar energy harvesting, but currently prone to a large hysteresis and current instability. Here, Xu et al. show improvements in a hybrid material in which the fullerene is distributed at perovskite grain boundaries and thus passivates defects effectively.

Spectroscopic measurements show how the features of the band structure related to the kagome lattice in CsV₃Sb₅ contribute to the observed strongly correlated phases.

Multiple complementary optical signatures confirm the persistence of ferroelectricity and inversion-symmetry-breaking magnetic order down to monolayer NiI₂, introducing the physics of type-II multiferroics into the area of van der Waals materials.

Multimetal oxyhydroxides are among the most active catalysts for alkaline water oxidation, but tuning their properties remains a challenge. Now, the performance of NiFe- and FeCo-based catalysts is optimized with the incorporation of high-valence modulator metals, which shifts the active metals towards lower valence states and enables lower overpotentials.

The kagome lattice is increasingly known as a host for correlated topological electronic states. Here, Ye et al. report quantum de Haas-van Alphen oscillations of a ferromagnetic kagome material Fe3Sn2, where bulk electronic Dirac fermions are found to be modulated by rotation of the magnetic moment.

The experimental realization of lattice-born flat bands with nontrivial topology has been elusive. Here, the authors observe topological flat bands near the Fermi level in a kagome metal CoSn, with flat bands as well as Dirac bands originating from 3d orbitals in a frustrated kagome geometry.

The many strongly interacting degrees of freedom in transition metal oxides make it difficult to capture and describe the nature of their metal-insulator transitions. Li et al. show that a resonant magnetic X-ray nanoprobe gives access to local critical behavior that is difficult to detect otherwise.

The role of disorder in the formation of charge density waves (CDWs) remains elusive in typical CDW materials. Here, the authors report coexisting diffraction signals and anomalous slow dynamics of charge domains near the CDW transition temperature in ZrTe\({}_{3}\), suggesting as fingerprints of pristine and disorder-perturbed CDWs.

Organohalide perovskites and preformed colloidal quantum dots are combined in the solution phase to produce epitaxially aligned ‘dots-in-a-matrix’ crystals that have both the excellent electrical transport properties of the perovskite matrix and the high radiative efficiency of the quantum dots.

The measurement of the charge density wave energy gap in high-temperature superconducting cuprates uncovers new links between competing states.

Water oxidation is key to the production of chemical fuels from electricity. Now, guided by theory, NiCoFeP oxyhydroxide catalysts have been developed that require an overpotential lower than that required by IrO₂. In situ soft X-ray absorption studies of neutral-pH NiCoFeP catalysts indicate formation of Ni⁴⁺, which is favourable for water oxidation.

Habituation is a learning mechanism that enables control over forgetting and learning. Zuo, Panda et al., demonstrate adaptive synaptic plasticity in SmNiO₃ perovskites to address catastrophic forgetting in a dynamic learning environment via hydrogen-induced electron localization.

Light-emitting diodes based on mixed-dimensionality perovskite solids show outstanding radiative properties in the near-infrared region.

Films of exfoliated crystals of two-dimensional hybrid metal halide perovskites with phenyl groups as organic cations show increased molecular rigidity, reduced electron–phonon interactions and blue emission with photoluminescence quantum yield approaching 80%.

Charge order has been established as a ubiquitous instability of the underdoped copper-oxide superconductors. New investigations reveal that it extends to the overdoped side of the phase diagram, a region otherwise known to host a conventional Fermi liquid state.

Nanoscale magnetic fluctuations are spatiotemporally resolved beyond conventional resolution limits using coherent correlation imaging, in which frames in Fourier space are recorded and analysed using an iterative hierarchical clustering algorithm.

A new form of charge ordering is observed in a cuprate superconductor. At low doping, a fully rotationally symmetric ordering appears before becoming locked to the Cu–O bond directions at high doping. The link between charge correlations and fermiology give a perspective on the phase diagram.

Few-layer magnetic materials sometimes show a different form of magnetism from their thicker equivalents. The authors contend that the mechanism is changes in the stacking order in the thin limit that modify the interlayer exchange interaction.

Fe₃Sn₂ hosts massive Dirac fermions, owing to the underlying symmetry properties of the bilayer kagome lattice in the ferromagnetic state and the atomic spin–orbit coupling.

The recent discovery of superconductivity in bilayer nickelates under high pressure offers a new material platform to explore high-temperature superconductivity. In this study, the authors identify the electronic ground states of the La₃Ni₂O₇ film at ambient pressure revealing the critical role of ligand oxygen and the existence of long-range spin ordering along with charge-like anisotropy.

Application of an electric field changes the transport and optical properties of samarium nickelate submerged in water, making it a suitable passive sensor of weak electric fields in salt water.

The recent discovery of superconductivity in the nickelates provides another angle to investigate this phenomenon in the high-T_c cuprates and hopefully help solve the mechanism of their unconventional superconductivity. Here, the authors report an increase in T_c for Pr_0.8Sr_0.2NiO₂ where strain from the underlying LSAT substrate plays a possible role, supporting simulations also reveal the contributing role Ni and O orbitals hybridisation play in the unconventional pairing.