Letters

The spatial separation of charge and spin densities in one-dimensional electron systems is the hallmark of Tomonaga–Luttinger physics. Waveform measurements now provide direct evidence for spin–charge separation.

When the entropy of a system scales as a function of its surface area, rather than its volume, it is said to obey an entropy area law. Now, an area law is shown to exist numerically in the entanglement entropy of superfluid helium.

With the help of a quantum simulator and Bayesian inference it is possible to determine the unknown Hamiltonian of a quantum system. An experiment demonstrates this using a photonic quantum simulator and a solid-state system.

Electrical rectification is usually achieved by layering p-type and n-type materials, but experiments now demonstrate rectification in a bulk polar semiconductor that has inversion-symmetry breaking and strong Rashba spin–orbit coupling.

Single photons stored in the collective Rydberg excitations of two atomic ensembles can interact with each other despite being micrometres apart.

The Berry curvature is essential to the study of the topological properties of a system, be it solid-state, atomic or photonic. In 1D photonic lattices there is a new clever way of measuring the Berry curvature.

Using two entangled optical beams and post-selection, a single photon can have the same effect as eight photons in terms of the induced phase shift. This example illustrates the power of the so-called weak-value amplification.

An excited two-level system emits a single photon, but in special circumstances it can emit two. The reason for this unexpected two-photon emission lies with modified Rabi oscillations.

Larmor coupling is a collisionless momentum exchange mechanism believed to occur in various astrophysical and space-plasma environments. The phenomenon is now observed in a laboratory experiment.

The success of machine learning techniques in handling big data sets proves ideal for classifying condensed-matter phases and phase transitions. The technique is even amenable to detecting non-trivial states lacking in conventional order.

A neural-network technique can exploit the power of machine learning to mine the exponentially large data sets characterizing the state space of condensed-matter systems. Topological transitions and many-body localization are first on the list.

A detailed analysis of low-temperature torsional oscillation measurements on two-dimensional ⁴He reveals evidence for intertwined superfluid and density wave order in this system.

A demonstration of switching between solitons of different chirality in a one-dimensional electronic system shows how topological excitations can be used to realize non-trivial algebraic operations.

Experiments show how domain walls can act as reservoirs of exchange energy that can be used to controllably launch or detect spin waves in ferromagnetic nanowires.

A laboratory study of turbulent flows reproduces the properties of jets in the atmospheres of gas giants, providing a better understanding of how these jets could extend deep into the planetary atmosphere.

Plasma optics enables the manipulation of highly intense laser beams. Now, plasma holograms, involving the creation of a modulated plasma surface on a solid target, are reported — for example, plasma hologram fork gratings produce optical vortices.

Unlike the usual picture of Anderson localization, in three-dimensional quasicrystals light waves can localize without disorder, thanks to their short mean free path.

Valleytronics — exploiting a system’s pseudospin degree of freedom — is being increasingly explored in sonic crystals. Now, valley transport of sound is reported for a macroscopic triangular-lattice array of rod-like scatterers in a 2D air waveguide.

Photoemission is usually driven by the energy of the illuminating laser pulses, but in the strong-field regime, the photoemission from an array of plasmonic nanoparticles is shown to be controlled by the light’s electric field.

Larval starfish use an outer layer of cilia to generate vortices in the fluid around their bodies. Spectacular imaging and mathematical modelling are combined to reveal that these dynamics are alternately optimized for swimming and feeding.