Research articles

Single-molecule transistors have enabled studies of magnetism and other correlated nanoscale behaviour, but superconductivity has not been observed with this approach. It is now shown that superconducting junctions on both sides of a C₆₀ molecule induce superconductivity across the whole device.

Spin-transfer torque allows the magnetization of nanopillar devices to be switched electrically. Incorporating asymmetries into the design of such a device generates a linear out-of-plane torque component that could help prevent the unwanted spontaneous reversal of the nanopillar’s magnetization.

Intense optical beams can alter the way that a material interacts with X-ray radiation. This is now demonstrated by experiments that use femtosecond laser pulses to affect inner-shell processes in neon atoms, increasing the transmission of X-rays. This could allow imprinting of optical pulse trains onto much longer X-ray pulses.

It has been suggested that the extreme states of matter generated by high-intensity lasers could allow conditions similar to those in the vicinity of black holes to be studied in the lab. The observation of striking similarities between the X-ray spectra emitted by a laser-driven laboratory plasma and those measured from two high-mass binary star systems suggests such potential has been realized.

A comprehensive survey of the cuprate, heavy-fermion and iron-based superconductors shows a universal linear relationship between their magnetic resonance energy and superconducting gap. This result suggests that antiferromagnetic fluctuations might have a similar role in the unconventional superconductivity of these seemingly different classes of materials.

The Mott transition between an insulator and a metal can be tuned by applying pressure, which affects the electronic correlations. In an insulating organic salt, NMR studies reveal that the spin fluctuations are suppressed whereas the conductance is enhanced by the same critical exponent as pressure drives the insulator into a bad metal.

Anisotropies in the response of ferromagnetic electrodes attached to a gold nanoparticle lead to Coulomb blockade and spin-valve-like magnetoresistance phenomena. Such behaviour could allow the development of magnetically gated single-electron transistors composed of just two terminals.

Optical tweezers use the forces exerted by light to manipulate objects at the micrometre scale. An approach in which the target particle itself plays an active part now achieves this using a lower light intensity. This reduction means that heat-sensitive targets such as viruses could be manipulated directly.

The spin state of two electrons in a double well is a promising qubit. Now, such qubits can be arbitrarily rotated around two different axes by applying a magnetic field of different magnitude to each electron. This can be done in nanoseconds, before the stored information is lost.

Graphene is expected to possess characteristics that are particularly useful for transporting and manipulating electronic spin. The discovery of spin-dependent interference features in its electrical characteristics could be useful in the development of graphene spintronics.

Coupling a nanometre-scale oscillator to a micrometre-scale optical resonator provides a way of measuring the small-amplitude motion. The scheme is applied to silicon nitride ’strings’, but it could be extended to many other types of tiny vibrating structures.

Ferromagnetism usually only occurs in materials containing elements that form covalent 3d and 4f bonds. Its occurrence in pure carbon is therefore surprising, even controversial. A systematic magnetic force microscope study indicates that ferromagnetism in graphite is the result of localized spins that arise at grain boundaries.

Optical lattices, generated by interfering laser beams, provide a platform for observing condensed-matter phenomena in ultracold-atom systems. By extending the lattice idea to a multimode cavity, it should be possible to observe even more complex effects, such as frustration, crystallization, glass phases and supersolidity.

A study of a one-dimensional system may have finally resolved the long-standing discrepancy between the expected and measured inelastic neutron scattering intensities in the high-temperature cuprate superconductors.

Complex oxide films are highly anisotropic in the way they conduct electricity, which is due to phase separation. However, the origin of this metal–insulator phase coexistence has been unclear. Transport measurements now show that strain, rather than chemical inhomogeneity, is mainly responsible.

The ‘transmon’ design for superconducting qubits is particularly promising, owing to the long coherence times that it enables. Now, high-fidelity single-shot readout of such qubits — necessary for operating a quantum processor — has been demonstrated

High-intensity X-ray sources such as synchrotrons and free-electron lasers need large particle accelerators to drive them. The demonstration of a synchrotron X-ray source that uses a laser-driven particle accelerator could widen the availability of intense X-rays for research in physics, materials science and biology.

The presence of disorder makes it difficult to determine the intrinsic properties of graphene in its ideal form. Measurements of high-quality bilayer graphene flakes suspended above a substrate identify the persistence of quantum Hall behaviour at magnetic fields an order of magnitude lower than seen before, and previously unseen symmetry breaking of the lowest Landau level is also observed.

Owing to the fact that graphene is just one atom thick, it has been suggested that it might be possible to control its properties by subjecting it to mechanical strain. New analysis indicates not only this, but that pseudomagnetic behaviour and even zero-field quantum Hall effects could be induced in graphene under realistic amounts of strain.

Similar to atoms in cold gases, exciton–polaritons in semiconductor microcavities can undergo Bose–Einstein condensation. A striking consequence of the appearance of macroscopic coherence in these systems is superfluidity. Now, clear evidence for such behaviour has been found in an exciton–polariton condensate.