Volume 12 Issue 4, April 2016

Two experiments with ultracold fermionic and bosonic atoms in optical superlattices demonstrate the quantized charge transport predicted by Thouless in the 1980s.

Disentangling the physics of the pseudogap phase from the other electronic phases of high-temperature superconductors has long been a frustrating problem. A recent high-field experiment has isolated it completely — thus raising hopes that its origin can finally be understood.

The first results from the NOvA experiment confirm what we already know about neutrino oscillations. As data collection continues we are getting closer to finding the remaining unknown parameters.

The quality and quantity of current and forthcoming cosmological datasets call for both analytical and numerical modelling of the dynamics of nonlinear gravitational matter based on general relativity.

Charge transport in a cyclically time-modulated periodic potential, also known as a topological Thouless pump, has been realized in an ultracold gas of fermionic atoms.

Experimentally probing the dynamics of laser–plasma interactions is hard, owing to the nature of the relevant temporal and spatial scales at play. Ptychography, a phase-problem solving technique, can help the analysis of such interaction measurements.

Time- and angle-resolved photoelectron spectroscopy experiments are used to monitor the transition between Floquet–Bloch and Volkov states in the topological insulator Bi₂Se₃.

A systematic spectroscopic analysis of the principal members of the iron pnictide family of superconductors reveals a substantial spin–orbit splitting.

Josephson junctions based on graphene exhibit tunable proximity effects. The appearance of superconducting states when changing magnetic field and carrier concentration has now been investigated—some proximity effect survives for fields above 1 T.

An upconversion from negatively charged to neutral excitons is observed in monolayer tungsten diselenide, which could provide a route for cooling two-dimensional semiconductors using lasers.

Andreev reflection occurs at the interface of a metal and a superconductor when an incident electron in the metal gets ‘reflected’ as a hole travelling on the same path. Replace the metal with graphene and specular reflection may instead take place.

The creep motion of domain walls in magnetic metals can belong to different universality classes depending on whether they are driven by magnetic fields or spin-polarized currents.

Crystal symmetries may protect single Dirac cones on the surface of a photonic crystal, creating a photonic analogue of a three-dimensional solid-state topological insulator.

Hydrodynamic coupling induces a vortex state in bacterial populations. Microfluidic experiments and modelling now demonstrate that lattices of these vortices can self-organize into patterns characterized by ferro- and antiferromagnetic order.

When general relativity is included in large-scale simulations of the cosmic structure of the Universe, relativistic effects turn out to be small but measurable, thus providing tests for models of dark matter and dark energy.

Thouless introduced the idea of a topological charge pump: the quantized motion of charge due to the slow cyclic variation of a periodic potential. This topologically protected transport has now been realized with ultracold bosonic atoms.

Exploiting lasers for accelerating charged particles to relativistic velocities has long been theoretically considered. Now, applying a plasma mirror for injecting electrons into an intense laser field in vacuum is shown to lead to such acceleration.

The dynamic susceptibility of the quantum spin ice material Yb₂Ti₂O₇ is probed by means of time-domain spectroscopic techniques, providing a handle on the conductivity of monopole excitations in this system.

Cells break their symmetry to migrate, switching between protrusive and retractive edge activity to move directionally. Experiments and simulations reveal that this mode switching relies on a mechanism that depends on distance to the cell’s centre.

Vincent Icke paints a portrait of the bewildering cosmological constant.