Research articles

Connecting complex networks is known to exacerbate perturbations and lead to cascading failures, but natural networks of networks are surprisingly stable. A theory now proposes that network structure holds the key to understanding this paradox.

Spin relaxation in graphene is much faster than theoretically expected. Now, a scenario based on a mixing of spin and pseudospin degrees of freedom and defect-induced spatial spin–orbit coupling variations predicts longer spin relaxation times.

Two concentric carbon nanotubes don’t need to have a common finite unit cell. Absorption spectra of such incommensurate double-walled carbon nanotubes reveal strong hybridization of the electron wavefunctions — unusual for van der Waals-coupled structures. The observations can be rationalized by zone folding the electronic structure of twisted-and-stretched graphene bilayers.

The interaction of a quantum system with its surroundings is usually detrimental, introducing decoherence. Experiments now show how such interactions can be harnessed to provide all-optical control of the spin state of a quantum dot.

Repeatedly probing a quantum system restricts its evolution, providing a route for state engineering. Such confinement, described by quantum Zeno dynamics, has now been implemented to generate superposition states in a multi-level Rydberg atom.

Strontium titanate is a common substrate for growing oxide heterostructures—from superconductors to interfaces that support several phases of matter. But in an all-strontium-titanate device with a liquid electrolyte and metal-oxide gate, the results are anything but common.

Electrons in graphene have a pseudospin, but controlling this degree of freedom is challenging. Evidence now suggests that the moiré superlattices arising in two-dimensional heterostructures can be used to electrically manipulate pseudospins.

Using the two stable electronic states of alkaline-earth atoms, an orbital spin-exchange interaction—the building block of orbital quantum magnetism—has been observed in a fermionic quantum gas.

In a topological material, Weyl fermions—with relativistic and Newtonian characteristics—at a quantum critical point couple to the Coulomb interaction, leading to an anisotropic screening such that the fermions are effectively non-interacting.

A class of van der Waals universality is introduced in the collision dynamics of three identical ultracold atoms at all scattering lengths. It is insensitive to short-range chemical details and can be computed using two-body parameters only.

Quantized resistivity values for 2D electron systems don’t necessarily result from an external magnetic field as in the ‘normal’ quantum Hall effect; they can arise due to a material's intrinsic ferromagnetism too—the quantum anomalous Hall effect. Experiments with a ferromagnetic topological insulator now establish how the anomalous states can be mapped onto the normal states.

Hybridized systems offer a promising route for developing quantum devices, but inhomogeneous broadening limits the practical use of large spin ensembles. Suppression of the decoherence induced by such broadening has now been demonstrated for a superconducting cavity coupled to an ensemble of nitrogen–vacancy centres in diamond.

Fetching an object by means of sending a wave—impossible? Not necessarily. As now demonstrated experimentally, generating waves on a water surface using a set of plungers can cause a floating particle to move counter to the general direction of wave propagation. The effect originates from vorticity creation by steep 3D waves.

Electron energy-loss spectroscopy uses inelastically scattered electrons to provide information about a material’s chemical composition. It is now shown that localized plasmonic excitations can lead to nonlinear scattering, significantly enhancing the signals arising from inelastic electrons.

The conducting surface states of 3D topological insulators are two-dimensional. In an analogous way, the edge states of 2D topological insulators are one-dimensional. Direct evidence of this one-dimensionality is now presented, by means of scanning tunnelling spectroscopy, for bismuth bilayers—one of the first theoretically predicted 2D topological insulators.

The shakti lattice describes a new type of frustration not found in naturally occurring materials. Fabrication of the first artificial spin-ice array displaying shakti dynamics confirms the locally ordered, globally degenerate nature of these exotic lattice structures.

Majorana fermions, which are their own antiparticles, are expected to exist in topological superconductors. A study using superconducting leads in contact with a quantum well reveals the presence of supercurrents along one-dimensional sample edges of a quantum spin Hall state. These edge supercurrents are topological.

Wound repair is thought to involve cell migration and the contraction of a tissue-level biopolymer ring—invoking analogy with the pulling of purse strings. Traction-force measurements now show that this ring engages the tissue's surroundings to steer migration, prompting revision of the purse-string mechanism.

Numerical evidence now supports the idea that a liquid–liquid transition forms a generic feature of tetrahedrally coordinated liquids. This result establishes the physical validity of such a transition and provides a possible explanation for the anomalous behaviour of liquid water.

In a Josephson junction, a current flows from one superconductor to another through a barrier without any voltage being applied. SQUIDs, for example, are based on this phenomenon. Now, an iron-based multi-band superconductor shows signs of intrinsic Josephson junctions, opening up prospects for applications.