Flash Physics: No WIMPs for HESS, graphene production ramps up in China, double-helix semiconductor

Photograph of several of the HESS Cherenkov telescopes
In the dark: the HESS observatory has not spotted any WIMPs

HESS dark-matter search comes up empty after 10 years

The High Energy Stereoscopic System (HESS) observatory in Namibia has failed to find any evidence of dark matter in the inner halo of the Milky Way after ten years of observation. HESS uses an array of ground-based telescopes to observe the Cherenkov light that is created when a high-energy cosmic gamma ray interacts with the atmosphere. The Milky Way halo should harbour large amounts of dark matter, which, if described correctly by the weakly interacting massive particle (WIMP) model, should annihilate to create gamma rays. However, HESS has been unable to measure an excess of gamma rays coming from that region between 2004–2014, as described in Physical Review Letters. While no hint of dark matter was seen, the measurements allow physicists to fine-tune the WIMP model by putting a new limit on how likely the hypothetical particles are to annihilate.

Commercial graphene production begins in China

The first facility for the commercial production of graphene in China has started operations in Xiamen. The material is being made by the Hengli Shengtai company, which is controlled by the graphene scientist Bor Jang, who is co-founder of the US-based graphene maker Angstron Materials. Graphene production by Hengli Shengtai is expected to reach 5000 tonnes per year by 2020. Dubbed the “wonder material”, graphene is a sheet of carbon just one atom thick. It has a number of desirable properties such as high electron mobility and high mechanical strength, and is already used to make mobile-phone display screens. This video explains how graphene is made at a lab in Manchester UK.

Double-helix semiconductor is flexible and robust

Photograph of needles of the flexible semiconducting material
Fuzzy logic: filaments of the double-helix semiconductor

An inorganic material with a double-helix structure has been discovered by Daniela Pfister and colleagues at the Technical University of Munich. Made up of tin, iodine and phosphorus, the material is a semiconductor, which the researchers say has extraordinary optical and electronic properties. The double-helix-like structure makes the material flexible, yet robust – which is unlike conventional inorganic semiconductors. Indeed the material, called SnIP, is so flexible that centimetre-long fibres can be bent without breaking. “This property of SnIP is clearly attributable to the double helix,” says Pfister, adding that it can be easily produced “on a gram scale and is, unlike gallium arsenide, which has similar electronic characteristics, far less toxic.” The material will be described in a paper in Advanced Materials and could be used in a range of applications including solar-cell energy, sensors and optoelectronic devices.

Federico Capasso wins 2016 Balzan Prize for Applied Photonics

Harvard University physicist Federico Capasso has won the 2016 Balzan Prize for Applied Photonics for his work on the development of quantum cascade lasers and “major contributions in plasmonics and metamaterials”. The prize, worth 750,000 Swiss francs (£580,000), will be presented during a ceremony in Rome on 17 November. In announcing the award, Carlo Wyss, a former director for accelerators at CERN, hailed Capasso’s “pioneering work in the quantum design of new materials with specific electronic and optical features”, which were crucial to the realization of quantum cascade lasers. Recently, Capasso has made significant progress in the development of flat lenses, which could find use in mobile phones and other consumer electronics.

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