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Researchers use an optical vortex beam to create a stable pattern of electron spins in a thin layer of semiconductor material.

Spin-based electronic, or “spintronic,” devices can benefit from techniques that coax electron spins into static spatial patterns called spin textures. A new experiment demonstrates that an optical vortex—a light beam that carries orbital angular momentum—can generate a stable spin texture in a semiconductor [1]. The research team showed that the vortex generates a pattern of stripes that has potential uses in processing spin information. Previous experiments have optically stimulated these striped textures, but the optical vortex has a structure that approximately overlaps with the stripe pattern, allowing faster spin-texture formation.

The spins of unbound electrons in a material can be aligned by a magnetic field or by polarized light. But as these electrons move—either through diffusion or through conduction—their spins will begin to rotate in response to so-called spin-orbit interactions within the material. The direction and rate of these rotations for any given electron depend on the path that it takes. Thus, two nearby electrons that start out aligned will become misaligned as they move along different paths, even if they arrive at the same destination. So maintaining an electronic spin texture seems like a doomed enterprise.

A white dwarf star can explode as a supernova when its mass exceeds the limit of about 1.4 solar masses. A team led by the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching and involving the University of Bonn has now found a binary star system in which matter flows onto the white dwarf from its companion.

The system was found due to bright, so-called super-soft X-rays, which originate in the nuclear fusion of the overflowed gas near the surface of the white dwarf. The unusual thing about this source is that it is helium and not hydrogen that overflows and burns. The measured luminosity suggests that the mass of the white dwarf is growing more slowly than previously thought possible, which may help to understand the number of supernovae caused by exploding white dwarfs. The results have been published in the journal Nature.

Exploding white dwarfs are not only considered the main source of iron in the universe, they are also an important tool for cosmology. As so-called Type Ia supernovae (SN Ia), they all become roughly equally bright, allowing astrophysics a precise determination of the distance of their host galaxies.

One of the best ways to learn about any historical period is by conversing with the people who lived through it. Speaking with people from the distant past is very one-sided, as they are typically dead and have stopped listening long ago. However, they speak volumes if you have the patience to listen, or rather, read what they say in letters, diaries and primitive post-it notes with no sticky back sides.

An international group of computer scientists from Italy, the U.K. and Pakistan have teamed up to resurrect the dead from writings that have been degraded by time by developing a computer-assisted method to virtually return documents to a more legible and decipherable condition. In their research paper, “Restoration and content analysis of ancient manuscripts via color space based segmentation,” published in the journal PLOS ONE, the team details their digital restoration technique’s method and experimental results.

We get a sense of ancient civilizations from their writings, both trivial and profound. The Sumerian cuneiform writing on clay tablets reveals 4,000-year-old merchant transactions, geometric calculations, and poetry detailing the fall of a great city. Had they been written on paper and not in clay we would likely not have them today.

Graphene is one of the strongest materials. On top of that, it is exceptionally good at conducting heat and electrical currents, making it one of the most special and versatile materials we know. For all these reasons, the discovery of graphene was awarded the Nobel Prize in Physics in 2010.

Yet, many properties of the material and its cousins are still poorly understood—for the simple reason that the atoms they are made up of are very difficult to observe. A team of researchers from the University of Amsterdam and New York University have now found a surprising way to solve this issue.

Two-dimensional materials, consisting of a hyper-thin single layer of atomic crystal, have attracted a lot of attention recently. This well-deserved attention is mainly due to their unusual properties, very different from their three-dimensional ‘bulk’ counterparts. Graphene, the most famous representative, and many other two-dimensional materials, are nowadays researched intensely in the laboratory.

Michael Levin is a biologist at Tufts University working on novel ways to understand and control complex pattern formation in biological systems.

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Michael’s Twitter: https://twitter.com/drmichaellevin.
Michael’s Website: https://drmichaellevin.org.

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