Reviews & Analysis

Anisotropies in conductivity measurements of bismuth point to the spontaneous breaking of intrinsic degeneracies in its electronic structure — and suggest there may be still more to learn from this well-studied material.

Is it possible for a metal to exist in a strictly two-dimensional system? This may seem trivial, but it is actually a longstanding problem. The electrical characteristics of an array of superconducting islands on a normal metal suggests that the answer could be 'yes'.

Vast amounts of data are available about complex technological systems and how we use them. These data provide the basis not only for mapping out connectivity patterns, but also for the study of dynamical phenomena, including epidemic outbreaks and routing of information through computer networks. This article reviews the fundamental tools for modelling such dynamical processes and discusses a number of applications.

Networks have proved to be useful representations of complex systems. Within these networks, there are typically a number of subsystems defined by only a subset of nodes and edges. Detecting these structures often provides important information about the organization and functioning of the overall network. Here, progress towards quantifying medium- and large-scale structures within complex networks is reviewed.

Aspects concerning the structure and behaviours of individual networks have been studied intensely in the past decade, but the exploration of interdependent systems in the context of complex networks has started only recently. This article reviews a general framework for modelling the percolation properties of interacting networks and the first results drawn from its study.

A completely ordered universe is as unexciting as an entirely disordered one. Interesting ‘complex’ phenomena arise in a middle ground. This article reviews the tools that have been developed to quantify structural complexity and to automatically discover patterns hidden between order and chaos.

An experimental technique based on Doppler velocimetry provides a detailed picture of electronic spins as they diffuse, drift and turn under the action of an electric field in a two-dimensional electron gas.

The realization of a single-particle Stirling engine pushes thermodynamics into stochastic territory where fluctuations dominate, and points towards a better understanding of energy transduction at the microscale.

Topological defects are encountered in fields ranging from condensed-matter physics to cosmology. These broken-symmetry objects are intrinsically local, but theoretical work now suggests that non-local quantum superpositions of such local defects might arise in a quantum phase transition.

An open quantum system loses its 'quantumness' when information about the state leaks into its surroundings. Researchers now show how this decoherence can be controlled between two incompatible regimes in the case of a single photon.

The realization that primordial black holes produce oscillations when they pass through stars brings us one step closer to observing traces of this dark-matter candidate that formed in the early Universe.

Monolayer graphene is a semimetal with no bandgap, and bilayer graphene is a semiconductor with a tunable gap. A trio of studies now shows that trilayer graphene can be either, depending on how its layers are stacked — behaviour that could support exotic new electronic states.

Manipulating the electrons trapped in quantum-dot pairs is seen as one possible route to quantum computation. This idea is now extended to three quantum dots, enabling a whole host of extended functionality.

Fibre networks inspire an update to a century-old criterion for mechanical integrity — showing that a little bending resistance can go a long way.

Defects in diamond crystals possess rare physical properties that can enable new forms of technology. Unlocking this potential requires rapid quantum-state measurement, a 'quantum snapshot', which has now been achieved.