Letters

The dynamics of spins in single atomic layers of cuprates and other compounds are important for understanding their properties, such as magnetism and high-temperature superconductivity. Now, spin excitations in isolated single layers of a cuprate have been measured, providing valuable feedback on their magnetic properties.

The electronic interactions at the interface of oxide materials promise properties that can be very different from those of the parent compounds. The finding that many-body interactions in oxide superlattices can be used to engineer electronic properties offers a new strategy for designing oxide heterostructures.

Multiferroics show simultaneous electrical and magnetic order. The suggestion that ferroelectricity in an organic multiferroic is not driven by the usual atomic displacements but instead by ordering of electronic charges opens the possibility of a new group of multiferroic compounds.

The motion of dislocations under stress is a key process in crystal plasticity. The finding that at low temperatures differences between experiments and theoretical predictions of dislocation activation can be explained by quantum effects arising from crystal zero-point vibrations represents a significant advance in our understanding of plasticity.

Van der Waals interactions are critical to the understanding of functional metal/molecule interfaces in catalysis, molecular electronics and self-assembly. Such interactions have now been characterized at the single-molecule level through a combination of measurements of the stretching mechanics of molecular junctions and atomistic simulations.

Heterostructures of very thin films have been used for decades in research and industry. Now a transmission electron microscopy study demonstrates the possibility of realizing perfect structures built by piling up one-atom-thick layers of graphene and boron nitride.

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.

Graphene is often referred to as the strongest material in existence. That may be so for a perfect crystal, but most graphene sheets are polycrystalline, and the grain boundaries affect their mechanical properties. A new study reveals that both the density and detailed arrangement of the defects that form the grain boundaries play a significant part in determining the strength of a polycrystalline graphene sheet.

Tissues with perfusable vascular networks can be fabricated through layer-by-layer assembly, bioprinting or sacrificial moulding, but current approaches are slow, have limited resolution, or place significant constraints on the materials or the processing conditions. A rapid and general vascular casting approach using carbohydrate glass as a sacrificial template to generate tissues containing cylindrical networks that can be lined with endothelial cells and perfused with blood under high-pressure pulsatile flow is now reported.

A thin layer of yttrium iron garnet coating on different materials can transform wasted heat into voltage. The process is based on the spin Seebeck effect and could lead to new types of application that make use of omnipresent wasted heat.

Replacing noble metals in heterogeneous catalysts by low-cost and ubiquitous substitutes such as iron is highly desirable especially because it does not bear potential health risks. A low cost and environmentally benign intermetallic compound Al₁₃Fe₄ is now identified as an active and selective semi-hydrogenation catalyst, which could prove to be applicable to a wide range of heterogeneously catalysed reactions.

Although fundamentally intriguing, iron-based superconductors have not been seriously considered for applications because of the limited superconducting current that has so far been observed in wires made from these materials. It is now shown that by following a specific synthesis procedure it is possible to achieve superconducting currents that are close to commercial requirements.

Conventional sensors generate a signal that is directly proportional to the concentration of the target molecule. Now, by means of an enzyme that controls the growth of silver nanocrystals on plasmonic transducers, a nanosensor with sensitivity that is inversely proportional to concentration and that can detect ultralow concentrations of the cancer biomarker prostate-specific antigen in whole serum is demonstrated.

Although intrinsic superconductivity in graphene has not been demonstrated yet, superconductivity in this material can be induced by the proximity effect. The deposition of metallic nanoparticles on a graphene layer allows the status of graphene to be tuned from insulating to superconducting. This metal–graphene hybrid material can therefore be seen as a model system to elucidate the properties of inhomogeneous superconductors.

Liquid-crystalline order can be templated in a material by refilling a photopolymerized liquid-crystal cast with the material after the non-polymerized portion has been washed out. This approach has now been used to template, in achiral liquid crystals, chiral three-dimensional blue phases with unprecedented thermal stability that are suitable for narrowband mirrorless lasing and switchable electro-optic devices.

The so-called pseudogap is a feature of high-T_c superconductors that has puzzled scientists since its discovery. It is of widespread opinion that this feature is associated with a structural symmetry breaking. Now, a highly sensitive scanning tunnelling microscopy experiment shows that a specific structural symmetry is not, as many believed, at the origin of the pseudogap state.

Geometrically frustrated magnets are systems where it is impossible for all magnetic interactions to occur simultaneously. The discovery of frustrated magnetism in a system where the magnetic moments are situated across clusters of transition-metal elements instead of individual ions promises a new approach for controlling such magnetic states.

Light absorption across the bandgap in semiconductors is exploited in many important applications such as photovoltaics, light-emitting diodes and photocatalytic conversion, but whether coloured metals can be used in such applications is unclear. A red metallic oxide Sr_1-xNbO₃ is now shown to be effective under visible light to photocatalyse the oxidation of methylene blue, and the oxidation and reduction of water.

The self-assembly of colloidal particles functionalized with complementary DNA strands into crystalline structures has been hampered by kinetic trapping into disordered aggregates, which effectively limits the temperature window where crystallization occurs. A strategy to design DNA-functionalized colloids with a broadened crystallization window is now proposed, and is supported by theory and simulations.

Although sodium is an abundant element that can be electrochemically and reversibly extracted from and inserted into layered materials, the resulting reversible capacity for storing energy remains low. A manganese–iron–sodium-based electrode is now shown to exhibit a reversible capacity of 190 mAh g⁻¹ due to electrochemically active Fe³⁺/Fe⁴⁺ redox reactions.