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Single X-ray pulse reveals plasma nanostructures across scales with one camera

Understanding instabilities and turbulence in plasmas is one of the key challenges across a wide range of plasma research fields, including nuclear fusion, astrophysics and laser-plasma physics. In plasmas, slight disturbances can grow due to instabilities, and energy is transferred between structures of various sizes due to turbulence. These phenomena give rise to structures ranging from very small to large, which significantly influence the overall motion and energy flow of the plasma.

Since structures generated by instabilities and turbulence vary with even slight differences in conditions, it is not easy to reproduce the same state in every experiment. Therefore, there is a need for “spatially multiscale single-shot measurements” that can simultaneously capture structures of a wide range of sizes in a single measurement. In particular, in high-energy-density plasmas, instabilities grow in an extremely short time, so high temporal and spatial resolution is also required to capture their initial stages.

By combining the newly developed “beamstop-free X-ray small-angle scattering method” with an X-ray free-electron laser and a microscale rod assembly target, an international research group, led by Assistant Professor Masato Ota of the National Institute for Fusion Science (then a graduate student at the Graduate School of Science, Osaka University), Associate Professor Yoichi Sakawa of the Institute of Laser Engineering, Osaka University, succeeded in measuring the structural collapse and rarefaction processes of high-energy-density plasma across a wide range of spatial scales—from 10 nm to 500 nm—with sub-picosecond temporal resolution.

Diamond defects confirm 80-year-old theory of crystal stress

For the first time, researchers in Japan have directly mapped several components of the stress field surrounding an atomic-scale flaw in the crystal structure of diamond. Led by Tokuyuki Teraji at Japan’s National Institute for Materials Science, the team achieved its result using nitrogen-vacancy (NV) centers in diamond, whose spin states respond differently to stress depending on how they are oriented relative to the stress field.

Published in Applied Physics Letters, the technique validates an 80-year-old theory about how miniature stress fields are distributed in diamond. It could also help improve the processes used to manufacture the high-quality diamond demanded by emerging technologies.

Metalens microscope switches focus with voltage, not moving optics

Just as it is difficult for a camera to keep both a nearby flower and a distant mountain sharply focused at the same time, conventional optical microscopes face a similar challenge when imaging structures located at different depths inside the body. Tighter focusing of light improves spatial resolution, but at the same time reduces the depth range over which the image remains sharply focused.

A joint research team led by professors Junsuk Rho and Chulhong Kim at POSTECH has developed a dual-focus metalens-based photoacoustic microscopy system that can switch between different imaging depths simply by controlling an applied voltage, without mechanically moving any optical components. The study is published in Light: Science & Applications.

Tunable gate electrodes could help semiconductors operate at lower voltages

Smartphones and computers process information by switching the current that flows inside semiconductors on and off. The gate electrode delivers the signal that controls this switching. Until now, gate electrodes have typically been made from metals whose electronic properties are fixed.

A KAIST-led joint research team has now built working semiconductor electrodes from a new material that combines metals and organic molecules. The study provides a basis for designing electrodes to meet the requirements of different semiconductors. It is also expected to support the development of low-power semiconductors that operate at lower voltages.

The study is published in the journal Advanced Materials.

Physicists reveal new paradigm for fiber growth in neurodegenerative diseases

Some proteins that are linked to neurodegenerative diseases can form both liquid droplets and amyloid fibers. But how are these two states connected, and where do the fibers grow? Leiden physicists Liru Feng and Louise Jawerth have discovered a counter-intuitive mechanism.

“We wanted to answer an open question: What happens to protein droplets as they age?” assistant professor Jawerth explains. “They look just like drops of oil in water, but they are droplets of proteins inside cells, also called condensates. Scientists have only relatively recently come to understand how they develop. Our findings on how they age— published in Nature Physics today—add an important piece to the puzzle.”

The droplets are very complex materials; they are liquid-like and can turn into solids that are glassy or fibrous. Jawerth states, “For 10 years or so, we have known that there is a link between fiber growth from these proteins and neurodegenerative disorders like Alzheimer’s disease or ALS. Our goal was to visualize, quantify and model this aging process, and we succeeded in doing so.”

One extra quantum dot helps balance speed and stability in spin qubits

Quantum computers need qubits that can be controlled both quickly and reliably. Yet making semiconductor spin qubits faster often makes them more sensitive to electrical noise, creating a difficult trade-off.

Researchers at the University of Osaka and their collaborators have now demonstrated a way to loosen this constraint by adding one extra quantum dot, allowing speed and noise resistance to be tuned more independently after the device has been made.

The research is published in the journal npj Quantum Information.

Tiny shifts in iron content tip a potential memory material between competing magnetic states

A team of Yale researchers has figured out what gives a magnetic material its mysterious properties, a discovery that could help boost computing memory and the field of “spintronics.” Their work is published in Physical Review Letters.

Iron-intercalated niobium disulfide (FeₓNbS₂) is a material in which iron atoms are inserted into the gaps between layers of niobium disulfide. Materials scientists have taken a great interest in the material because they can switch its resistance states by sending electrical current pulses through it.

“This is a very surprising thing, because usually it’s difficult to switch such states with electrical current at a low density,” said professor Yu He, who led the study. Wenxin Li, a Ph.D. student in He’s lab, is the first author.

Single optical element combines soft X-ray imaging and spectroscopy

An international research team from Germany, Switzerland and Japan has demonstrated in a recent study that a single reflection zone plate (RZP) can perform both soft X-ray imaging and resonant inelastic X-ray scattering (RIXS) mapping. The approach could simplify future instruments that need to determine both where structures are located in a material and how their electronic properties vary.

The study, which was published in Optics Express, was carried out at the P04 beamline of the PETRA III synchrotron radiation source at DESY in Hamburg. The researchers used an RZP, a precisely nanostructured reflective optic that simultaneously focuses and disperses soft X-rays. Conventional X-ray imaging provides spatial information about a sample, whereas spectroscopy reveals its electronic structure, chemical bonding and excited states.

Combining the two capabilities usually requires several optical components and demanding alignment procedures. In the new work, the RZP acts as an all-in-one element for reflection, focusing, imaging and spectral dispersion.

Patterns of polar vortices discovered in lead-free superlattices on silicon

A team at HZB has, for the first time, reported polar vortices in (BaTiO₃/SrTiO₃)₁₀ superlattices on silicon. These results expand the range of materials and substrates on which polar topological textures can occur and open up new options for incorporating complex ferroelectric states into silicon-based technologies.

Polar textures such as vortices have so far been observed almost exclusively in lead-containing superlattices comprising ultrathin ferroelectric and dielectric titanate layers on oxide substrates. The delicate balance between electrical forces, mechanical stresses (imposed by the substrate) and the energy required to change the direction of polarization leads to distinctive electrical dipole patterns in the ferroelectric layers.

In principle, structures with complex polar states could be used to develop novel components with specific functions, as the structures are small, stable and can be influenced by external electric fields. However, to achieve this, it would be important to replace the toxic lead and deposit the layers on silicon substrates, the ubiquitous platform of the semiconductor industry.

‘One-positron cyclotron’ could test a key prediction of the Standard Model

The positron is the antimatter counterpart of the electron, identical in mass but carrying an equal and opposite electric charge. Like the electron, it also behaves like a tiny bar magnet, and according to a key prediction of the Standard Model of particle physics, its magnetic moment should be exactly equal and opposite to the electron’s.

Through new research published in Physical Review Letters, Gerald Gabrielse and colleagues at Northwestern University in Illinois have unveiled a promising new way to test this assumption, by trapping a single positron in a “quantum cyclotron.”