Quasi-Dirac Monopoles

research highlights

Defective yet strong fundamental particle, the magnetic polymeric film, the researchers embedded Nature Commun. 5, 3186 (2014) monopole, with non-zero magnetic silver nanoparticles that have a localized monopole charge, has grasped the attention surface plasmon resonance in the blue With a tensile strength of over 100 GPa, of many. The existence of magnetic spectral range; the fabricated film therefore a pristine graphene layer is the strongest monopoles is now not only supported by the scatters this colour while being almost material known. However, most graphene work of Dirac, but by both the grand unified completely transparent in the remaining fabrication processes inevitably produce theory and string theory. However, both visible spectral range. The researchers a defective layer. Also, structural defects theories realize that magnetic monopoles suggest that dispersion in a single matrix of are desirable in some of the material’s might be too few and too massive to be metallic nanoparticles with sharp plasmonic technological applications, as defects allow detected or created in a lab, so physicists resonances tuned at different wavelengths for the opening of a bandgap or act as pores started to explore approaches to obtain will lead to the realization of multicoloured for molecular sieving, for example. Now, by such particles using condensed-matter transparent displays. LM tuning the exposure of graphene to oxygen systems. Now, Ray and co-workers report plasma to control the creation of defects, the latest observation of a Dirac monopole Ardavan Zandiatashbar et al. show that a quasiparticle (pictured), this time in a Facet formation Adv. Mater. http://doi.org/rb5 (2014) single layer of graphene bearing sp3-type spinor Bose–Einstein condensate. This defects (chemisorbed oxygen atoms) at a magnetic monopole quasiparticle is in fact high density (an average spacing between not a magnetic monopole fundamental defects of 5 nm) maintains its stiffness, and particle, but a quasiparticle equivalent, and that its breaking strength is only reduced is a source of a ‘synthetic magnetic field’ by 14%. Instead, the presence of vacancies that violates the zero-divergence law. Even (formed by the removal of carbon atoms though this system only resembles a true at higher oxygen-plasma exposure) causes magnetic monopole, this is the first time both mechanical properties to degrade such a quasiparticle has been detected significantly from those of the pristine layer. within a system governed by quantum field The researchers also show that Raman spectra theory, the framework behind subatomic can be mapped to the measured stiffness and particle physics. ON 1 µm

strength, thereby providing a non-destructive © 2014 WILEY method to predict these properties from the Plasmons on screen respective Raman parameters. PP Nature Commun. 5, 3152 (2014) Crystal facets result from anisotropic growth along different crystallographic directions Quasi-Dirac monopoles See-through displays are increasingly used and, as a consequence, do not usually exist Nature 505, 657–660 (2014) in aviation and automotive applications, for polycrystalline materials that have no as well as in gaming and entertainment. long-range order and grow isotropically. The most common technology used Now, Ullrich Steiner and colleagues show to fabricate them relies on transparent that faceted platinum particles (pictured), organic light-emitting diodes, but cheaper which are inherently polycrystalline, can and more scalable alternatives based on be isolated following electrochemical light-responsive elements dispersed in synthesis within mesoporous polymeric a glassy or polymeric matrix are being templates with double-gyroid morphology. studied at present. Following the latter Without such a template, spherical platinum

© 2014 NPG approach, Chia Wei Hsu and colleagues particles are produced. Faceted platinum now realize a transparent screen that particles with well-defined symmetries are Since the publication of Dirac’s classical displays bright, blue images projected onto made when the template has large double- paper in 1931, the search for a new it from a commercial laser projector. In a gyroid monodomains, however, if the double-gyroid morphology has randomly orientated multi-domains, an irregularly Motorizing graphene fibres Adv. Mater. http://doi.org/rbr (2014) faceted particle is formed. The particles made within the monodomain templates The practical potential of graphene fibres (GFs) stems from the fact they combine the are tetrahexahedral in shape, with 24 mechanical strength and flexibility of fibres with the electronic and thermal characteristics equal faces. Steiner and colleagues use a of graphene. Recently, a spinning technique for fabricating GFs directly from graphene oxide numerical model to explain the formation has galvanized research in this area, as this provides a large-scale and low-cost route to of the faceted particles and with the aid of fibres with a range of different functionalities that one can envisage being useful in textiles microscopic analysis, report a nucleation– for wearable electronics. Now, Liangti Qu and colleagues from the Beijing Institute of coalescence mechanism in which the Technology demonstrate an intriguing concept for GFs, in the form of moisture-operated growth front progresses along the centre of twisting graphene motors. Depending on the degree of twisting they are subjected to, the channels of the template. This causes different twist angles can be introduced in the GFs. Once a particular twist angle has been a slowing of growth in all directions — in set, it can be reversibly tuned by exposing the fibres to moisture. The authors then make use particular, in the 110 direction, yielding of this property to fabricate an electric generator in which the application of vapour leads the tetrahexahedra observed. AS to a twisted GF switching the magnetization of a small magnet, which in turn drives a small electric field in copper coils surrounding it. AT Written by Luigi Martiradonna, Olivia Nicoletti, Pep Pàmies, Alison Stoddart and Andrea Taroni.

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