Lifeboat Foundation

In a new realm of materials, PhD student Thanh Nguyen uses neutrons to hunt for exotic properties that could power real-world applications.

Thanh Nguyen is in the habit of breaking down barriers. Take languages, for instance: Nguyen, a third-year doctoral candidate in nuclear science and engineering (NSE), wanted “to connect with other people and cultures” for his work and social life, he says, so he learned Vietnamese, French, German, and Russian, and is now taking an MIT course in Mandarin. But this drive to push past obstacles really comes to the fore in his research, where Nguyen is trying to crack the secrets of a new and burgeoning branch of physics.

“My dissertation focuses on neutron scattering on topological semimetals, which were only experimentally discovered in 2015,” he says. “They have very special properties, but because they are so novel, there’s a lot that’s unknown, and neutrons offer a unique perspective to probe their properties at a new level of clarity.”

A device demonstrated in a groundbreaking new experiment acts like a laser, only backwards. And someday it might send power invisibly through the air.

At first glance, a pack of wolves has little to do with a vinaigrette. However, a team led by Ramin Golestanian, Director at the Max Planck Institute for Dynamics and Self-Organization, has developed a model that establishes a link between the movement of predators and prey and the segregation of vinegar and oil. They expanded a theoretical framework that until now was only valid for inanimate matter. In addition to predators and prey, other living systems such as enzymes or self-organizing cells can now be described.

Order is not always apparent at first glance. If you ran with a pack of wolves hunting deer, the movements would appear disordered. However, if the hunt is observed from a bird’s eye view and over a longer period of time, patterns become apparent in the movement of the animals. In physics, such behavior is considered orderly. But how does this order emerge? The Department of Living Matter Physics of Ramin Golestanian is dedicated to this question and investigates the physical rules that govern motion in living or active systems. Golestanian’s aim is to reveal universal characteristics of active, living matter. This includes not only larger organisms such as predators and prey but also bacteria, enzymes and motor proteins as well as artificial systems such as micro-robots. When we describe a group of such active systems over great distances and long periods of time, the specific details of the systems lose importance.

In a paper published this week in the journal Frontiers of Physics, a duo of researchers from Italy investigated the similarities between the network of neurons in the human brain and the cosmic network of galaxies.

For over a decade, theoretical physicists have predicted that the van Hove singularity of graphene could be associated with different exotic phases of matter, the most notable of which is chiral superconductivity.

A van Hove singularity is essentially a non-smooth point in the density of states (DOS) of a crystalline solid. When graphene reaches or is close to this specific energy level, a flat band develops in its electronic structure that can occupy an exceptionally large number of electrons. This leads to strong many-body interactions that promote or enable the existence of exotic states of matter.

So far, the exact degree to which the available energy levels of graphene need to be filled with electrons (i.e., “doped”) in order for individual phases to stabilize has been very difficult to determine using model calculations. Identifying or designing techniques that can be used to dope graphene to or beyond the van Hove singularity could ultimately lead to interesting observations related to exotic phases of matter, which could in turn pave the way towards the development of new graphene-based technology.

Theories on how the Milky Way formed are set to be rewritten following discoveries about the behavior of some of its oldest stars.

An investigation into the orbits of the Galaxy’s metal-poor stars—assumed to be among the most ancient in existence—has found that some of them travel in previously unpredicted patterns.

“Metal-poor stars—containing less than one-thousandth the amount of iron found in the Sun—are some of the rarest objects in the galaxy,” said Professor Gary Da Costa from Australia’s ARC Center of Excellence in All Sky Astrophysics in 3 Dimensions (ASTRO 3D) and the Australian National University.

So the Universe is getting hotter? 😃

For almost a century, astronomers have understood that the Universe is in a state of expansion. Since the 1990s, they have come to understand that as of 4 billion years ago, the rate of expansion has been speeding up.

As this progresses, and the galaxy clusters and filaments of the Universe move farther apart, scientists theorize that the mean temperature of the Universe will gradually decline.

Continue reading “Unexpectedly, The Universe Is Getting Hotter And Hotter as It Expands” »

Bringing huge amounts of protons up to speed in the shortest distance in fractions of a second—that’s what laser acceleration technology, greatly improved in recent years, can do. An international research team from the GSI Helmholtzzentrum für Schwerionenforschung and the Helmholtz Institute Jena, a branch of GSI, in collaboration with the Lawrence Livermore National Laboratory, U.S., has succeeded in using protons accelerated with the GSI high-power laser PHELIX to split other nuclei and to analyze them. The results have now been published in the journal Nature Scientific Reports and could provide new insights into astrophysical processes.

For less than one picosecond (one trillionth of a second), the PHELIX laser shines its extremely intense light pulse onto a very thin gold foil. This is enough to eject about one trillion hydrogen nuclei (protons), which are only slightly attached to the gold, from the back-surface of the foil, and accelerate them to high energies. “Such a large number of protons in such a short period of time cannot be achieved with standard acceleration techniques,” explains Pascal Boller, who is researching laser acceleration in the GSI research department Plasma Physics/PHELIX as part of his graduate studies. “With this technology, completely new research areas can be opened that were previously inaccessible.”

These include the generation of nuclear fission reactions. For this purpose, the researchers let the freshly generated fast protons impinge on uranium material samples. Uranium was chosen as a case study material because of its large reaction cross-section and the availability of published data for benchmarking purposes. The samples have to be close to the proton production to guarantee a maximum yield of reactions. The protons generated by the PHELIX laser are fast enough to induce the fission of uranium nuclei into smaller fission products, which remain then to be identified and measured. However, the laser impact has unwanted side effects: It generates a strong electromagnetic pulse and a gammy-ray flash that interfere with the sensitive measuring instruments used for this detection.

O,.o.

Physicists from MIPT and Vladimir State University, Russia, have converted light energy into surface waves on graphene with nearly 90% efficiency. They relied on a laser-like energy conversion scheme and collective resonances. The paper was published in Laser & Photonics Reviews.

Manipulating light at the nanoscale is a task crucial for being able to create ultracompact devices for optical energy conversion and storage. To localize light on such a small scale, researchers convert optical radiation into so-called surface plasmon-polaritons. These SPPs are oscillations propagating along the interface between two materials with drastically different refractive indices—specifically, a metal and a dielectric or air. Depending on the materials chosen, the degree of surface wave localization varies. It is the strongest for light localized on a material only one atomic layer thick, because such 2-D materials have high refractive indices.

Continue reading “No losses: Scientists stuff graphene with light” »