Archive for the ‘materials’ category: Page 114

Apr 11, 2021

Long Live Superconductivity! Short Flashes of Laser Light With Sustaining Impact

Posted by in categories: materials, quantum physics

Superconductivity – the ability of a material to transmit an electric current without loss – is a quantum effect that, despite years of research, is still limited to very low temperatures. Now a team of scientists at the MPSD has succeeded in creating a metastable state with vanishing electrical resistance in a molecular solid by exposing it to finely tuned pulses of intense laser light. This effect had already been demonstrated in 2016 for only a very short time, but in a new study the authors of the paper have shown a far longer lifetime, nearly 10000 times longer than before. The long lifetimes for light-induced superconductivity hold promise for applications in integrated electronics. The research by Budden et al. has been published in Nature Physics.

Superconductivity is one of the most fascinating and mysterious phenomena of modern physics. It describes the sudden loss of electrical resistance in certain materials when they are cooled below a critical temperature. However, the need for such cooling still limits the technological usability of these materials.

In recent years, research by Andrea Cavalleri’s group at the MPSD has revealed that intense pulses of infrared light are a viable tool to induce superconducting properties in a variety of different materials at much higher temperatures than would be possible without photo-stimulation. However, these exotic states have so far persisted for only a few picoseconds (trillionths of a second), thus limiting the experimental methods for studying them to ultrafast optics.

Apr 8, 2021

Glass molded like plastic could usher in new era of complex glass shapes

Posted by in category: materials

Injection molded glass could revolutionize production of telecom equipment.

Apr 8, 2021

A graphene system that freezes electrons as the temperature rises

Posted by in categories: materials, particle physics

Two teams of researchers have independently found that there exists a certain type of graphene system where electrons freeze as the temperature rises. The first team, with members from Israel, the U.S. and Japan, found that placing one layer of graphene atop another and then twisting the one on top resulted in a graphene state in which the electrons would freeze as temperatures rose. And in attempting to explain what they observed, they discovered that the entropy of the near-insulating phase was approximately half of what would be expected from free-electron spins. The second team, with members from the U.S., Japan and Israel, found the same graphene system and in their investigation to understand their observations, they noted that a large magnetic moment arose in the insulator. Both teams have published their results in the journal Nature. Biao Lian with Princeton University has published a News and Views piece outlining the work by both teams in the same journal issue.

As temperatures around most substances rise, the particles they are made of are excited. This results in solids melting to liquids and liquids turning to a gas. This is explained by thermodynamics—higher temperatures lead to more , which is a description of disorder. In this new effort, both teams found an exception to this rule—a graphene system in which electrons freeze as the .

The graphene system was very simple. Both teams simply laid one sheet of on top of another and then twisted the top sheet very slightly. But it had to be twisted at what they describe as the “magic angle,” describing a twist of just 1 degree. The moiré pattern that resulted led to lower velocity of the electrons in the system, which in turn led to more resistance, bringing the system close to being an insulator.

Apr 2, 2021

Breaking ultrawide-bandgap semiconductor records is just like baking bread

Posted by in categories: energy, materials

Researchers have made unparalleled ultrawide-bandgap semiconductors through temperature and timing, just like baking bread.

Alloying, the process of mixing metals in different ratios, has been a known method for creating materials with enhanced properties for thousands of years, ever since copper and tin were combined to form the much harder bronze. Despite its age, this technology remains at the heart of modern electronics and optics industries. Semiconducting alloys, for instance, can be engineered to optimize a device’s electrical, mechanical and optical properties.

Alloys of oxygen with group III elements, such as aluminum, gallium, and indium, are important semiconductor materials with vast applications in high-power electronics, solar-blind photodetectors and transparent devices. The defining property of a semiconductor is its bandgap, a barrier over which only electrons with the required energy can pass. Beta-phase aluminum gallium oxides are notable because of their relatively large bandgap, but most III-O alloys are expensive to make and of unsatisfactory quality.

Apr 2, 2021

How Gary Dickerson Unleashes The Magic In Silicon Chips

Posted by in categories: computing, materials

Applied Materials CEO Gary Dickerson’s formula for success isn’t magic. “Being close to the customer,” he said, is the lesson that’s guided him.

Apr 1, 2021

Lab-made hexagonal diamonds stiffer than natural diamonds

Posted by in categories: materials, physics

Nature’s strongest material now has some stiff competition. For the first time, researchers have hard evidence that human-made hexagonal diamonds are stiffer than the common cubic diamonds found in nature and often used in jewelry.

Named for their six-sided , hexagonal diamonds have been found at some meteorite impact sites, and others have been made briefly in labs, but these were either too small or had too short of an existence to be measured.

Now scientists at Washington State University’s Institute for Shock Physics created hexagonal diamonds large enough to measure their stiffness using . Their findings are detailed in a recent paper in Physical Review B.

Apr 1, 2021

New theory suggests uranium ‘snowflakes’ in white dwarfs could set off star-destroying explosion

Posted by in categories: cosmology, materials

A pair of researchers with Indiana University and Illinois University, respectively, has developed a theory that suggests crystalizing uranium “snowflakes” deep inside white dwarfs could instigate an explosion large enough to destroy the star. In their paper published in the journal Physical Review Letters, C. J. Horowitz and M. E. Caplan describe their theory and what it could mean to astrophysical theories about white dwarfs and supernovas.

White dwarfs are small stars that have burned up most of their nuclear fuel—they are typically much cooler than they once were and are very dense. In this new effort, Horowitz and Caplan used data from the Gaia space observatory to theorize that sometimes small grains of uranium could begin to crystalize (due to enriched actinides), forming what they describe as snowflakes. They suggest this could happen because of the differing melting points of the material involved. They further suggest that if this were to occur, it could lead to splitting of atomic nuclei, resulting in a series of fission reactions as the solids become enriched in actinides. And if such reactions were to raise the temperature of the interior of the star by igniting carbon, the result would likely be merging of atomic nuclei and eventually a very large fusion reaction that would result in a large explosion—likely large enough to destroy the star.

Mar 24, 2021

Cosmic Inflation Was Likely Not A One-Off Event, Says Astronomer

Posted by in categories: cosmology, materials

“Whooshes of creation” may be producing multiverses at this moment, says astronomer.

The cosmic inflation credited with creating the homogeneous universe which we now enjoy was likely not a one-off event, University of California, Berkeley astronomer Alexei Filippenko, told me. In fact, these ‘whooshes of creation’ may be producing multiverses even at this moment, says Filippenko.

The idea of an exponential, faster-than-light expansion of the early universe, was first put forth by MIT astrophysicist Alan Guth in 1981. And today, Inflation theory is used to explain the Cosmos’ current size, expansion, homogeneity and the fact that it appears to be geometrically flat, I noted in a 2011 issue of Astronomy magazine.

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Mar 19, 2021

GOTHAM Investigators Uncover Warehouse-Full of Complex Molecules Never Before Seen in Space

Posted by in categories: materials, space

Radio observations of a cold, dense cloud of molecular gas reveal more than a dozen unexpected molecules.

Scientists have discovered a vast, previously unknown reservoir of new aromatic material in a cold, dark molecular cloud by detecting individual polycyclic aromatic hydrocarbon molecules in the interstellar medium for the first time, and in doing so are beginning to answer a three-decades-old scientific mystery: how and where are these molecules formed in space?

“We had always thought polycyclic aromatic hydrocarbons were primarily formed in the atmospheres of dying stars,” said Brett McGuire, Assistant Professor of Chemistry at the Massachusetts Institute of Technology, and the Project Principal Investigator for GOTHAM, or Green Bank Telescope (GBT) Observations of TMC-1: Hunting Aromatic Molecules. “In this study, we found them in cold, dark clouds where stars haven’t even started forming yet.”

Mar 13, 2021

3D Printed Organs

Posted by in categories: biotech/medical, materials

A new technique for making 3D printed organs uses hydrogels and lasers to print at speeds 50 times faster than conventional methods.