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Unlike the other iron-based superconductors, the parent compounds of the alkaline iron selenide superconductors are insulators. Dai and colleagues examine the spin-wave excitations in these materials and uncover evidence for a common magnetic origin for all iron-based superconductors.

Intercalating alkali metals into picene—a hydrocarbon with five linearly fused benzene rings—results in superconducting materials. Now, alkali-metal-doped phenanthrene, which consists of three fused benzene rings, is also found to be superconducting, opening up a broader class of organic superconductors.

Superconductivity in the iron pnictides is believed to be related to quantum critical fluctuations. Putzke et al. observe unexpected anomalies in the critical fields of BaFe₂(As_1−xP_x)₂that emerge close to its magnetic critical point, which they argue is a generic feature of quantum critical superconductivity.

In some iron-based materials, unconventional superconductivity can emerge near a quantum phase transition where long-range magnetic order vanishes. Giovannettiet al.show that the magnetic quantum phase transition in an iron pnictide superconductor is very close to the quantum tricritical point.

High critical temperature superconductors could be used to produce ideal electric power lines, but the misalignment of crystalline grain boundaries reduces current density. Here, pnictide superconductors are found to be more tolerant to misaligned grain boundaries than cuprates.

In high-temperature superconductors, a very low density of states, the pseudogap, exists even above the critical temperature. Here, the authors show that this is also the case for a conventional superconductor, titanium nitride thin films, and that this pseudogap is induced by superconducting fluctuations.

Up to now, all iron-based high-T_c superconductors contain a square iron lattice. Here, Wang et al. report the observation of superconductivity in an iron honeycomb lattice accompanied with pressure-driven spin-crossover, in-plane lattice collapse and insulator-metal transition.

A galvanic strategy enables the intercalation of diverse molecular cations into bulk and few-layer van der Waals crystals under mild conditions, yielding 50 organic–inorganic superlattices. This method enables the definition of vertical and lateral intercalation heterostructures, opening avenues for the device integration of hybrid quantum materials.

Observation of a many-body pairing gap in a trapped, 2D atomic Fermi gas shows that ultracold atomic gases can be used to emulate the physics of correlated 2D superconductors, with the ultimate goal of understanding high-temperature superconductivity.

The interaction between electrons and phonons is important for many materials properties. The finding that phonon modes of a superconducting thin film can influence the properties of an adjacent normal conductor, even over comparatively long distances, suggests new ways of controlling electron–phonon interactions.

While superconductivity experts investigate the fundamental properties of iron pnictides, it is worth wondering whether the properties of these materials are good enough for applications. A strategy for growing high-quality BaFe₂As₂ thin films shows that the use of an appropriate buffer layer allows very high critical currents to be reached.

The superconducting phase of a superconductor is often one of several competing types of electronic order, including antiferromagnetism and charge density waves. For some superconductors, the superconducting transition temperature can be maximized by forcing the critical temperature of the competing order down to zero. Now, a related effect has been identified in a high-temperature superconductor, with the application of pressure yielding a striking two-step increase in the transition temperature.

The oxygen interstitials in the layers separating the superconducting CuO₂ planes undergo ordering phenomena in La₂CuO_4+y that enhance the transition temperature (T_c). It is also known that complex systems often have a scale-invariant structural organization, but hitherto none had been found in high-T_c materials. These authors report that the ordering of oxygen interstitials in the La₂O_2+y spacer layers of La₂CuO_4+y high-T_c superconductors is characterized by a fractal distribution up to a maximum limiting size of 400 µ.

Iron-based superconductors all share the same building blocks. So why do local magnetic properties vary from one compound to another? A new theoretical model explains the variation in physical properties and links it to the structural differences, providing a description for a wide range of materials.

Understanding the structural rearrangements of infinite-layer transition metal oxides at the atomic level remains challenging. Now in situ electron microscopy has been used to monitor the formation of infinite-layer SrFeO₂ through an oxygen deintercalation process; lattice flexibility of the FeO_x polyhedral layers facilitates the phase transformation.

Energy alignment in molecular tunnelling junctions is desirable for altering their electrical properties, however controllability is still an issue. Here the authors report a 2 orders-of-magnitude increase in the tunnelling current via chemical control of the energy-level alignment at a two-terminal junction.

In BaFe₂As₂, the lattice couples strongly to the magnetic and electronic degrees of freedom, providing a way to control them. Here, by means of time-resolved X-ray scattering, the authors measure rapid lattice oscillations, which can induce changes in the material’s electronic and magnetic properties.

Understanding spin dynamics in the cuprates is vital to understanding the origin high-temperature superconductivity. X-ray and neutron spectra obtained by Ishii et al.suggest that the spins in electron-doped cuprates are itinerant, in contrast to recent evidence that in hole-doped cuprates they are localized.

LiTi₂O₄is the only known spinel oxide superconductor, but systematic investigations of its transport properties have been lacking so far. Here, the authors' analyses detect an unusual magnetoresistance, revealing spin-orbit fluctuations similar to those in high-temperature superconductors.

A fully quantum mechanical description of the thermal Hall effect in high-temperature cuprate superconductors remains elusive. Here, by connecting it to momentum space Berry phases, the authors calculate the dependence of the intrinsic thermal Hall conductivity on temperature, external field and pairing gap.

The pairing symmetry of the wavefunction in high-T_ciron-based superconductors remains not completely understood. To shed light on this problem, here the authors investigate the local destruction of superconductivity by introducing Zn impurities in the BKZn iron arsenide compound.

Near to the superconducting state, cuprates display spatially-periodic charge density variations. Here, the authors use x-ray diffraction to determine the microscopic structure, showing how charge density waves in underdoped YBa₂Cu₃O_6.54break the symmetry of the superconducting layers.

The structure of the superconducting gap of iron pnictide superconductors is controversial. In this paper, angle-resolved specific heat measurements are used to show that the gap is anisotropic, which is consistent with an extended s-wave model of superconducting pairing.

The lanthanum-hydrogen system has attracted attention following the observation of superconductivity in LaH₁₀ at near-ambient temperatures and high pressures. Here authors describe the high-pressure syntheses of seven La-H phases; they report crystal structures and remarkable regularities in rare-earth element hydrides.

Current synthesis of 2D crystalline superconductors mainly limits them to layered materials. Now, crystalline, non-layered 2D PdTe has been synthesized by inducing interfacial reactions at a solid–solid interface, exhibiting 2D superconductivity with a thickness-dependent onset critical temperature of ~2.56 K.

When hydronium ions are enriched in confined water, short hydrogen bonds (SHBs) form due to the constrained space of excess protons between pairs of water molecules. Here authors demonstrate a SHB network confined on the surface of ionic COF membranes with tunable -SO₃H groups, with proton conductivity of 1389 mS cm^-1 at 90 ^oC.

Magnetic molecules have long been seen to hold promise in magnetic sensing applications. In this paper, Serrano et al show that a single layer of a magnetic molecule, a terbium based complex, is sensitive to the local magnetic field variation of a superconducting surface on which it is deposited.

High throughput manufacturing of long length coated conductors requires fast epitaxial growth of high-temperature superconducting films. Here, Soler et al. report an ultrafast growth rates and high critical current densities of YBa₂Cu₃O₇ films using a transient liquid-assisted growth method.

Room-temperature superconductivity is observed in a photochemically synthesized ternary carbonaceous sulfur hydride system at 15 °C and 267 GPa.

Hydrogen-rich superhydrides are promising high-temperature superconductors which have been observed only at pressures above 170 GPa. Here the authors show that CeH₉ can be synthesized at 80-100 GPa with laser heating, and is characterized by a clathrate structure with a dense 3-dimensional atomic hydrogen sublattice.

Two-dimensional superconductors will likely have applications not only in devices, but also in the study of fundamental physics. Here, Wang et al. demonstrate the CVD growth of superconducting NbSe2 on a variety of substrates, making these novel materials increasingly accessible.

Reports of superconductivity in K_xPicene spurred interest in alkali-intercalated polyaromatic hydrocarbon (PAH) compounds, but their compositions and structures have remained unclear. Now crystalline K₂Pentacene and K₂Picene — neither of which are superconducting — have been prepared by mild synthesis. Structural analysis shows that the cation sites arise within the molecular layers from reorientation of the PAHs within a herringbone packing.

Cooperative electronic properties that arise purely from carbon π-electrons can lead to unconventional superconductivity and quantum magnetism. New packing architectures have now been established in two caesium-intercalated polyaromatic hydrocarbons, CsPhenanthrene and Cs₂Phenanthrene, both strongly correlated multi-orbital Mott insulators. The frustrated magnetic topology in CsPhenanthrene also renders it a spin-½ quantum spin liquid candidate.

Isolated Au–B covalent bonds can be stabilized by bulky ligands or cluster confinement, but translating such bonds into an infinite solid has remained elusive. Here, the authors use crystal structure search with first-principles calculations at high pressure to identify a family of ternary compounds featuring Au–B covalent frameworks, M₂AuB₆ (M = Na, K, Mg, Ca, and Sr), and show that increased electron phonon-coupling stemming from Au−B bond stretching can lead to superconductivity in Na₂AuB₆ and K₂AuB₆.