Volume 14 Issue 4, April 2018

The variety of emergent phenomena occurring at oxide interfaces has made these systems the focus of intense study in recent years. We argue that spin–orbit effects in oxide interfaces provide a versatile handle to generate, control and convert spin currents, with a view towards low-power spintronics.

Enabled by recent advances in symmetry and electronic structure, researchers have observed signatures of unconventional threefold degeneracies in tungsten carbide, challenging a longstanding paradigm in nodal semimetals.

The ultimate regime of turbulence has been observed, more than half a century after its first prediction. Inspiration for achieving this technical feat came from the imperfections of an everyday pipe.

It seems obvious that restricting travel should help prevent the surge of epidemics. But a new mathematical analysis now demonstrates that mobility often reduces the heterogeneity in population distributions, thereby lowering the epidemic risk.

Active galactic nuclei are firm favourites to be revealed as the source of cosmic rays, but solid evidence has proven elusive. A model taking both local and global nuclei propagation into account may help to close the deal.

Quantized Majorana conductance is a hallmark of topological superconductors, but its fragility has made it difficult to observe. Device improvements have now enabled its measurement, making everyone eager to see the next step — topological qubits.

Turbulence in pipe flows causes substantial friction and economic losses. The solution to appease the flow through pipelines might be, counterintuitively, to initially enhance turbulent mixing and get laminar flow in return.

Stanene is a single sheet of tin atoms. Here, it is shown that a few stacked layers of stanene can be a superconductor. Changing the thickness of the substrate modifies the form of superconductivity and critical temperature.

Triply degenerate electronic structure—three-component fermions—protected by crystal symmetries is observed in tungsten carbide. The observed Fermi arcs associated with the surface states provide evidence of the non-trivial topology of the states.

A microfocused angle-resolved photoemission spectroscopy study of single layers of WS₂ on hexagonal boron nitride reveals that, upon electron doping, trionic interactions cause a giant increase of the spin splitting in the valence band.

A combined theoretical and experimental study of plasmonic nanostructures reveals a self-hybridization effect that arises from the non-Hermitian eigenmodes of localized surface plasmons.

Photon correlation measurements in driven-dissipative systems reveal the dynamical properties of dissipative phase transitions, as shown for optical bistability of cavity polaritons in GaAs.

Pump–probe measurements of CuB₂O₄ reveal non-reciprocal directional dichroism, demonstrating the possibility to optically induce magnetoelectricity in a material on a femtosecond timescale.

Coupling strengths differ between neighbours in square artificial spin ices, resulting in the loss of degeneracy. Introducing mesospins on vertices of the array alleviates this problem, by tuning the strength and ratio of the interaction energies.

Whether spatial order is required for structures that support topological modes remains unclear. Amorphous arrangements of interacting gyroscopes suggest that topology arises in materials for which the only design principle is the local connectivity.

Turbulence in pipe flows causes substantial friction (and therefore economic) losses. An experimental and numerical study now shows a solution might be to initially enhance turbulent mixing, which subsequently leads to a collapse of turbulence.

Taking into account the spatial distribution of population and its mobility, a reaction–diffusion model of an epidemic process reveals several different critical regimes, in which human mobility may even be detrimental to the spread of the disease.

A model that accounts for the high-energy neutrino, gamma-ray and ultrahigh-energy cosmic-ray emissions is proposed, suggesting that they emerge from the cosmic rays accelerated by the black-hole jets in galaxy clusters.

Many-body effects in an interacting spin-orbit coupled Fermi gas are studied with the help of clock spectroscopy. The results provide a simple view of how strong collective dynamics arise from local interactions in the presence of spin–orbit coupling.

A large-scale density matrix renormalization group study of the dipolar Heisenberg model reveals evidence for quantum spin liquid ground states on both triangular and kagome lattices.

Helical modes are induced in a high-mobility two-dimensional electron gas without strong spin–orbit coupling. This platform provides a versatile playground for investigating compounded quantum Hall edge states.

Turbulence is seldom confined by boundaries that are perfectly smooth, but wall roughness is usually ignored. A study of flows between rotating cylinders suggests that roughness enhances turbulent transport and alters its scaling behaviour.

Mark Keller explains how the elementary charge will soon be reinstated in metrology — and why it got sidelined in the first place.