Volume 10 Issue 12, December 2014

Monolayer films of iron selenide deposited on strontium titanate display signatures of superconductivity at temperatures as high as 109 K. These recent developments may herald a flurry of exciting findings concerning superconductivity at interfaces.

The old adage that you can't tango alone is certainly true for humans. But recent experiments show that it may also be applicable to Rydberg atoms, which keep a beat through the coherent exchange of energy.

Solitons in attractive Bose–Einstein condensates are mesoscopic quantum objects that may prove useful as tools for precision measurement. A new experiment shows that collisions of matter-wave bright solitons depend crucially on their relative phase.

Non-reciprocal components are useful in microwave engineering and photonics, but they are not without their drawbacks. A compact design now provides non-reciprocity without resorting to magnets or nonlinearity.

Stretching a sheet of graphene could induce a superconducting state. Similar strain-induced superconductivity may be realized at the interface between a topological crystalline insulator and a trivial band insulator.

Dark matter remains experimentally elusive. But what if it is more classical than expected, resembling a spatially varying field? A network of atomic clocks would be able to detect its variations.

Ferroelectric polarization vortices close to a ferroelectric transition turn out to be striking models of the cosmos in which strings are thought to have condensed out of the rapid expansion of the early Universe.

The on-line isotope separation technique for the production of accelerated beams of radioactive ions has led to important advances in our understanding of atomic nuclei. These are now reviewed, and further prospects are discussed.

Rydberg atoms offer an avenue for quantum simulation of many-body problems, but evidence for the coherent nature of their interaction is indirect. An externally-tuned resonance now reveals coherent oscillations between two single Rydberg atoms.

Atomic matter waves provide a controllable platform for studying the behaviour of solitons. In a lithium condensate, a characterization of the dynamics of collisions between solitons reveals a dependence on their relative phases.

Communication systems require non-reciprocal electromagnetic propagation, which is difficult to realize in circuits. An alternative is demonstrated by modulating the phase of strongly coupled resonators in a circular configuration.

A Fulde–Ferrell–Larkin–Ovchinnikov superconductor comprises pairs of fermions with non-zero momentum, which form alternating superconducting and normal regions in a magnetic field. NMR measurements now provide microscopic evidence for such a state.

A proposal for detecting dark matter originating from light fields rather than particles makes use of existing networks of atomic clocks to measure time discrepancies between clocks that are spatially separated.

Coupling the fluorescence of cold atoms to plasmons propagating on a gold surface offers a means of controlling the radiation from optical emitters without the need for a cavity.

Supersymmetry and Majorana fermions that are their own antiparticles are both concepts from particle physics that may become testable in condensed-matter systems. The observation of Cooper pairs in a helical Dirac gas brings this goal a step closer.

A variational approach for a three-band model provides deeper insights into the dynamics of a hole doped into an antiferromagnetic layer, with important implications for theories of high-temperature superconductivity.

Experimentalists have observed the predicted half-integer quantum Hall effect using the topological insulator BiSbTeSe₂, which exhibits topological surface states at room temperature, with each surface contributing a half quantum of Hall conductance.

In topological crystalline insulators, crystal symmetries give rise to particular electronic structures. As now shown, strain further induces pseudo-Landau states in IV–VI heterostructures—a mechanism possibly responsible for the superconductivity observed in such systems.

An imaging study of vortex proliferation near a continuous phase transition in a ferroelectric reveals frozen-in vortices that follow the predictions of the Kibble–Zurek model for cosmological strings formed in the early Universe.

The universal challenge.