Over the last 15 years, the content ofNature Physicshas covered an enormous breadth of subjects at the forefront of physics. The journal's past and present editors recount their favourite papers and what made chaperoning them to publication special.

Iron phthalocyanine (FePc) is a molecular semiconductor whose building blocks are 1D ferromagnetic chains. It is shown that its optical and magnetic properties are controlled by the growth strategy, obtaining extremely high coercivities of over 1 T and modulating the exchange constant between 15 and 29 K through switching from thin films with controlled orientations, to ultralong nanowires. Magnetization measurements are analyzed using concepts and formulas with broad applicability to all 1D ferromagnetic chains. They show that FePc is best described by a xy model with moments preferentially lying in the molecular planes. The chain Hamiltonian is very similar to that for the classic inorganic magnet CsNiF3, but with ferromagnetic rather than antiferromagnetic interchain interactions. The dominant degrees of freedom are topological excitations called solitons, namely moving 1D magnetic domain walls, and at low temperatures and fields a “super‐Curie–Weiss” law characteristic of nearly 1D xy and Heisenberg ferromagnets, where susceptibility scales as 1/(T2–θ2), is observed. The ability to control the molecular orientation and ferromagnetism of FePc systems, and produce them on flexible substrates, together with excellent transistor characteristics reported previously for phthalocyanine analogues, makes them potentially useful for magneto‐optical and spintronic devices.

Lasers have long held allure for physics, the military and science fiction, finds Luke Fleet. Lasers have long held allure for physics, the military and science fiction, finds Luke Fleet.

While organic semiconductors provide tantalizing possibilities for low-cost, light-weight, flexible electronic devices, their current use in transistors-the fundamental building block-is rather limited as their speed and reliability are not competitive with those of their inorganic counterparts and are simply too poor for many practical applications. Through self-assembly, highly ordered nanostructures can be prepared that have more competitive transport characteristics; however, no simple, scalable method has been discovered that can produce devices on the basis of such nanostructures. Here, we show how transistors of self-assembled molecular nanowires can be fabricated using a scalable, gradient sublimation technique, which have dramatically improved characteristics compared to those of their thin-film counterparts, both in terms of performance and stability. Nanowire devices based on copper phthalocyanine have been fabricated with threshold voltages as low as -2.1 V, high on/off ratios of 105, small subthreshold swings of 0.9 V/decade, and mobilities of 0.6 cm2/V s, and lower trap energies as deduced from temperature-dependent properties, in line with leading organic semiconductors involving more complex fabrication. High-performance transistors manufactured using our scalable deposition technique, compatible with flexible substrates, could enable integrated all-organic chips implementing conventional as well as neuromorphic computation and combining sensors, logic, data storage, drivers, and displays.

Evidence is mounting for the idea that living systems -such as flocks of birds and schools of fish -sit close to a critical point.But what if the social behaviour of monkeys was also influenced by criticality?Bryan Daniels and colleagues sought to find out, by examining the distribution of fight sizes in a population of pigtailed macaques (Macaca nemestrina; pictured).They found signs that these primates indeed hover near a tipping point, trading a certain robustness for the adaptability associated with criticality.But more surprising, perhaps, was the indication that they actively tune their distance from criticality by exploiting the group's heterogeneity.Daniels et al. looked at fight sizes from a group of 48 monkeys, defining an operational definition of criticality for finite systems based on the Fisher information and a collective instability measure.They found that the influence the monkeys had over the collective fight-joining behaviour was heterogeneous, and that the monkeys with the greatest sway over average fight sizes were those with the most control over changes in sensitivity.How well these ideas map to us higher primates remains to be seen.

Are you one of those regarding tax evasion as a very noble form of sports? If so you are exposing yourself to the increased risk of criminal prosecution by fiscal authorities and – in case of detection – serving as a deterrent paradigm for this kind of behavior. Likewise with “sins of omission” in road traffic such as “forgetting” to put on the safety belt or the crash helmet. Observing an accident – possibly even with fatal consequences – will remind us of that, at least for a little while. Let us finally think about consuming an (il)legal substance such as nicotine, alcohol or cocaine. Quite often it is just a small step to escalated from occasional use to addiction. Physical, psychological, social and economic suffering associated with abuse, however, gives clear evidence of the considerable risk already associated with occasional use. What is common to these examples from daily life, even if not necessarily your own?

In relativistic systems, information propagation is bounded by the speed of light, giving rise to the light-cone structure in Minkowski spacetime.A similar constraint exists in non-relativistic local quantum spin systems, known as the Lieb-Robinson bound.This provides a maximum propagation speed of entanglement and correlation, in turn leading to an effective spacetime light-cone.Now Thomas Hartman and colleagues have shown that consistency of diffusive transport with this light-cone places an upper bound on diffusivity.Relating three independent quantitiesdiffusivity, equilibration timescale and lightcone velocity -this upper bound is found to hold in a variety of physical systems in both regimes of strong and weak coupling.The result has wide implications, including a generalization of the Drude formula giving the lower bound of electrical resistivity in the absence of long-lived quasiparticles, and a relation between hydrodynamic and leading non-hydrodynamic modes in black holes.It will also motivate more systematic studiesfor example, using ultracold quantum gases and unconventional metals, for simultaneous determination of the three quantities involved in setting the bound.