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A micrometre-scale device that exploits the piezoresistive characteristics of silicon acts like an engine, converting heat into mechanical work in one mode of operation, and, in another, like a refrigerator, suppressing mechanical fluctuations.
Photoemission measurements sensitive to the momentum perpendicular to the layers that make up the pnictide superconductors are able to map out a full three-dimensional superconducting gap structure.
The nature of the percolation transition—how links add to a system until it is extensively connected—crucially underlies the structure and function of virtually all growing complex networks. Percolation transitions have long been thought to be continuous, but recent numerical work suggests that certain percolating systems exhibit discontinuous phase transitions. This study explains the key microscopic mechanisms underlying such ‘explosive percolation’.
Instead of the usual chemical doping or applied pressure methods for controlling quantum phase transitions, it’s now possible to break chemical bonds to tune into a ferromagnetic quantum critical point.
Intuition suggests that the occurrence of large quantum fluctuations should prevent a material from forming a glass by enabling its atoms to rearrange into a lower-energy ordered state. But new simulations suggest the opposite could be true, with fluctuations sometimes enhancing glass formation.
A tour-de-force study finds that as the pressure of lithium is increased to 50 GPa, its melting point drops to 190 K—the lowest yet observed of any elemental metal. The results suggest lithium could be a promising candidate for exploring exotic states of matter similar to that predicted for metallic hydrogen.
The effects of disorder on the electrical characteristics of graphene are found to change drastically in a magnetic field. At zero field, disorder simply causes charge scattering. But at high fields it induces the formation of a network of quantum dots.
A demonstration of the use of laser-driven plasma accelerators to generate electron beams having sharp temporal features of durations approaching 1 femtosecond, and currents of 3–4 kiloamperes, improves the outlook for using these devices in the development of compact free-electron lasers
