BLOGS

Researchers have synthesized sheets of gold that are one atom thick. Credit: imaginima/Getty

Topics: Graphene, Materials Science, Nanoengineering, Nanomaterials, Solid-State Physics

It is the world’s thinnest gold leaf: a gossamer sheet of gold just one atom thick. Researchers have synthesized¹ the long-sought material, known as goldene, which is expected to capture light in ways that could be useful in applications such as sensing and catalysis.

Goldene is a gilded cousin of graphene, the iconic atom-thin material made of carbon that was discovered in 2004. Since then, scientists have identified hundreds more of these 2D materials. But it has been particularly difficult to produce 2D sheets of metals, because their atoms have always tended to cluster together to make nanoparticles instead.

Researchers have previously reported single-atom-thick layers of tin² and lead³ stuck to various substances, and they have produced gold sheets sandwiched between other materials. But “we submit that goldene is the first free-standing 2D metal, to the best of our knowledge”, says materials scientist Lars Hultman at Linköping University in Sweden, who is part of the team behind the new research. Crucially, the simple chemical method used to make goldene should be amenable to larger-scale production, the researchers reported in Nature Synthesis on 16 April¹.

“I’m very excited about it,” says Stephanie Reich, a solid-state physicist and materials scientist at the Free University of Berlin, who was not involved in the work. “People have been thinking for quite some time how to take traditional metals and make them into really well-ordered 2D monolayers.”

In 2022, researchers at New York University Abu Dhabi (NYUAD) said that they had produced goldene, but the Linköping team contends that the prior material probably contained multiple atomic layers, on the basis of the electron microscopy images and other data that were published in ACS Applied Materials and Interfaces⁴. Reich agrees that the 2022 study failed to prove that the material was singler-layer goldene. The principal authors of the NYUAD study did not respond to Nature’s questions about their work.

Meet ‘goldene’: this gilded cousin of graphene is also one atom thick, Mark Peplow, Nature

Topics: Applied Physics, Civics, Materials Science, Solid-State Physics, Superconductors

I'm a person who will get Nature on my home email, my previous graduate school email (that's active because it's also on my phone), and my work email. Because it said "physics," I was primed to read it.

What I read made me clasp my hands over my mouth, and periodically stared at the ceiling tiles. My forehead bumped the desk softly, symbolically in disbelief.

Ranga Dias, the physicist at the center of the room-temperature superconductivity scandal, committed data fabrication, falsification and plagiarism, according to a investigation commissioned by his university. Nature’s news team discovered the bombshell investigation report in court documents.

The 10-month investigation, which concluded on 8 February, was carried out by an independent group of scientists recruited by the University of Rochester in New York. They examined 16 allegations against Dias and concluded that it was more likely than not that in each case, the physicist had committed scientific misconduct. The university is now attempting to fire Dias, who is a tenure-track faculty member at Rochester, before his contract expires at the end of the 2024–25 academic year.

Exclusive: official investigation reveals how superconductivity physicist faked blockbuster results

The confidential 124-page report from the University of Rochester, disclosed in a lawsuit, details the extent of Ranga Dias’s scientific misconduct. By Dan Garisto, Nature.

In a nutshell, this is the Scientific Method and how it relates to this investigation:

1. Ask a Question. It can be as simple as "Why is that the way it is?" The question suggests observation, as in, the researcher has read, or seen something in the lab that piqued their curiosity. It is also known as the problem the researcher hopes to solve. The problem must be clear, concise, and testable, i.e., a designed experiment is possible, a survey to gather data can be crafted.

2. Research (n): "the systematic investigation into and study of materials and sources in order to establish facts and reach new conclusions" (Oxford languages). Here, you are "looking for the gaps" in knowledge. People are human, and due to the times and the technology available, something else about a subject may reveal itself through careful examination. The topic area is researched through credible sources, bibliographies, similar published research, textbooks from subject matter experts. Google Scholar counts; grainy YouTube videos don't.

3. The Hypothesis. This encapsulates your research in the form of an idea that can be tested by observation, or experiment. The null hypothesis is a statement or claim that the researcher makes they are trying to disprove, and the alternate hypothesis is a statement or claim the researcher makes they are trying to prove, and with sufficient evidence, disproves the null hypothesis.

4. Design an Experiment. Design of experiments (DOE) follows a set pattern, usually from statistics, or now, using software packages to evaluate input variables, and judging their relationship to output variables. If it sounds like y = f(x), it is.

5. Data Analysis. "The process of systematically applying statistical and/or logical techniques to describe and illustrate, condense and recap, and evaluate data." Source: Responsible Conduct of Research, Northern Illinois University. This succinct definition is the source of my faceplanting regarding this Nature article.

6. Conclusion. R-squared relates to the data gathered, also called the coefficient of determination. Back to the y = f(x) analogy, r-squared is the fit of the data between the independent variables (x) and the output variables (y). An r-squared of 0.90, or 90% and higher, is considered a "good fit" of the data, and the experimenter can make predictions from their results. Did the experimenter disprove the null hypothesis or prove the alternate hypothesis? Were both disproved? (That's called "starting over.")

7. Communication. You craft your results in a journal publication, hopefully one with a high impact factor. If your research helps others in their research ("looking for gaps"), you start seeing yourself appearing in "related research" and "citation" emails from Google Scholar. Your mailbox will fill up, as I hope your self-esteem.

Back to the faceplant:

The 124-page investigation report is a stunning account of Dias’s deceit across the two Nature papers, as well as two other now-retracted papers — one in Chemical Communications³ and one in Physical Review Letters (PRL)⁴. In the two Nature papers, Dias claimed to have discovered room-temperature superconductivity — zero electrical resistance at ambient temperatures — first in a compound made of carbon, sulfur and hydrogen (CSH)¹ and then in a compound eventually found to be made of lutetium and hydrogen (LuH)².

Capping years of allegations and analyses, the report methodically documents how Dias deliberately misled his co-authors, journal editors and the scientific community. A university spokesperson described the investigation as “a fair and thorough process,” which reached the correct conclusion.

When asked to surrender raw data, Dias gave "massaged" data.

"In several instances, the investigation found, Dias intentionally misled his team members and collaborators about the origins of data. Through interviews, the investigators worked out that Dias had told his partners at UNLV that measurements were taken at Rochester, but had told researchers at Rochester that they were taken at UNLV."

Dias also lied to journals. In the case of the retracted PRL paper⁴ — which was about the electrical properties of manganese disulfide (MnS₂) — the journal conducted its own investigation and concluded that there was apparent fabrication and “a deliberate attempt to obstruct the investigation” by providing reviewers with manipulated data rather than raw data. The investigators commissioned by Rochester confirmed the journal’s findings that Dias had taken electrical resistance data on germanium tetraselenide from his own PhD thesis and passed these data off as coming from MnS₂ — a completely different material with different properties (see ‘Odd similarity’). When questioned about this by the investigators, Dias sent them the same manipulated data that was sent to PRL.

Winners and losers

Winners - Scientific Integrity.

The investigators of Nature were trying to preserve the reputation of physics and the rigor of peer review. Any results from any experiment has to be replicable in similar conditions in other laboratories. Usually, when retractions are ordered, it is because that didn't happen. If I drop tablets of Alka Seltzer in water in Brazil, and do it in Canada, I should still get "plop-plop-fizz-fizz." But the "odd similarity" graphs isn't that. The only differences between the two are 0.5 Gigapascals (10⁹ Pascals, 1 Pascal = 1 Newton/meter squared = 1 N/m²), the materials under test, and the color of the graphs. Face. Plant.

Losers - The Public Trust.

"The establishment of our new government seemed to be the last **great experiment** for promoting human happiness." George Washington, January 9, 1790

As you can probably tell, I admire Carl Sagan and how he tried to popularize science communication. But Dr. Sagan, Bill Nye the Science Guy, the canceled reality series Myth Busters (that I actually LIKED) has not bridged the gap between society's obsession with spectacle, and though the previously mentioned gentlemen and television show were promoting "science as cool," it is still a discipline, it takes work and rigor to master subjects that are not part of casual conversations, nor can you "Google." There are late nights solving problems, early mornings running experiments while everyone else outside of your library or lab window seems to be enjoying college life and what it can offer.

Dr. Dias is as susceptible to Maslow's Hierarchy of Needs (physical, safety, love and belonging, esteem, and self-actualization) as anyone of us. Some humans express this need posting "selfies" or social media posts "going viral," no matter how outrageous, or the collateral damage to the non-cyber real world. Or, they like to see their names in print in journals, filling their inboxes with "related research" or "citation" emails with their names attached. There is even currency now in your research being MENTIONED in social media.

*****

Mr. Halsey was the librarian at Fairview Elementary School in Winston-Salem, North Carolina. Everyone in my fifth grade class had to do a book report, but before we could do that, we had to pass Mr. Halsey's exam - with an 85% or better - on the Dewey Decimal System, and SHOW him in a practicum, that we could find a book that he would give you using Dewey. If you didn't pass, you didn't do the book report, and you failed English. I thankfully made an 92%, and satisfied Mr. Halsey that I wouldn't get lost in the periodicals.

We now have search engines that we can utilize via supercomputers in our hip pockets. A lot of effort to know math, physics, chemistry applied to the manufacture of semiconductors for those supercomputers instead of facilitating access to knowledge might have inadvertently manufactured a generation suffering from Dunning-Kruger. Networking those supercomputers over a worldwide web, coupled with artificial intelligence gives malevolent actors inordinate power over a captive audience of 8 billion souls.

Couple this with the falsification of data having a lease in the realm of science; it only contributes to the mistrust of institutions like the academy, like our democracy, which has been referred to since Washington as "the great experiment." If the null, and the alternate hypotheses are discarded, what pray tell, is on the other side of what we've always known?

 Graphical abstract. Credit: Joule (2024). DOI: 10.1016/j.joule.2024.01.025

Topics: Applied Physics, Chemistry, Energy, Green Tech, Materials Science, Photovoltaics

The energy transition is progressing, and photovoltaics (PV) is playing a key role in this. Enormous capacities are to be added over the next few decades. Experts expect several tens of terawatts by the middle of the century. That's 10 to 25 solar modules for every person. The boom will provide clean, green energy. But this growth also has its downsides.

Several million tons of waste from old modules are expected by 2050—and that's just for the European market. Even if today's PV modules are designed to last as long as possible, they will end up in landfill at the end of their life, and with them some valuable materials.

"Circular economy recycling in photovoltaics will be crucial to avoiding waste streams on a scale roughly equivalent to today's global electronic waste," explains physicist Dr. Marius Peters from the Helmholtz Institute Erlangen-Nürnberg for Renewable Energies (HI ERN), a branch of Forschungszentrum Jülich.

Today's solar modules are only suitable for this to a limited extent. The reason for this is the integrated—i.e., hardly separable—structure of the modules, which is a prerequisite for their long service life. Even though recycling is mandatory in the European Union, PV modules are, therefore, difficult to reuse in a circular way.

The current study by Dr. Ian Marius Peters, Dr. Jens Hauch, and Prof Christoph Brabec from HI ERN shows how important it is for the rapid growth of the PV industry to recycle these materials. "Our vision is to move away from a design for eternity towards a design for the eternal cycle," says Peters "This will make renewable energy more sustainable than any energy technology before.

The consequences of the PV boom: Study analyzes recycling strategies for solar modules, Forschungszentrum Juelich

A sample of the new titanium lattice structure 3D printed in cube form. Credit: RMIT. New titanium lattice structure 3D printed in cube form. Credit: RMIT

Topics: 3D Printing, Additive Manufacturing, Materials Science, Metamaterials

A 3D printed ‘metamaterial’ boasting levels of strength for weight not normally seen in nature or manufacturing could change how we make everything from medical implants to aircraft or rocket parts.

RMIT University researchers created the new metamaterial – a term used to describe an artificial material with unique properties not observed in nature – from common titanium alloy.

But it’s the material’s unique lattice structure design, recently revealed in the journal Advanced Materials, that makes it anything but common: tests show it’s 50% stronger than the next strongest alloy of similar density used in aerospace applications.

Nature-Inspired Designs and Innovations

Lattice structures made of hollow struts were originally inspired by nature: strong hollow-stemmed plants like the Victoria water lily or the hardy organ pipe coral (Tubipora musica) showed us the way to combine lightness and strength.

Supernatural Strength: 3D Printed Titanium Structure Is 50% Stronger Than Aerospace Alloy, SciTech Daily, RMIT University

TSMC is building Two New Facilities to Accommodate 2nm Chip Production

Topics: Applied Physics, Chemistry, Electrical Engineering, Materials Science, Nanoengineering, Semiconductor Technology

Realize that Moore’s “law” isn’t like Newton’s Laws of Gravity or the three laws of Thermodynamics. It’s simply an observation based on experience with manufacturing silicon processors and the desire to make money from the endeavor continually.

As a device engineer, I had heard “7 nm, and that’s it” so often that it became colloquial folklore. TSMC has proven itself a powerhouse once again and, in our faltering geopolitical climate, made itself even more desirable to mainland China in its quest to annex the island, sadly by force if necessary.

Apple will be the first electronic manufacturer to receive chips built by Taiwan Semiconductor Manufacturing Company (TSMC) using a two-nanometer process. According to Korea’s DigiTimes Asia, inside sources said that Apple is "widely believed to be the initial client to utilize the process." The report noted that TSMC has been increasing its production capacity in response to “significant customer orders.” Moreover, the report added that the company has recently established a production expansion strategy aimed at producing 2nm chipsets based on the Gate-all-around (GAA) manufacturing process.

The GAA process, also known as gate-all-around field-effect transistor (GAA-FET) technology, defies the performance limitations of other chip manufacturing processes by allowing the transistors to carry more current while staying relatively small in size.

Apple to jump queue for TSMC's industry-first 2-nanometer chips: Report, Harsh Shivam, New Delhi, Business Standard.

Credit: Public Domain

Topics: Applied Physics, Education, History, Materials Science, Philosophy, Radiation, Research

We take for granted that Earth is very old, almost incomprehensibly so. But for much of human history, estimates of Earth’s age were scattershot at best. In February 1907, a chemist named Bertram Boltwood published a paper in the American Journal of Science detailing a novel method of dating rocks that would radically change these estimates. In mineral samples gathered from around the globe, he compared lead and uranium levels to determine the minerals’ ages. One was a bombshell: A sample of the mineral thorianite from Sri Lanka (known in Boltwood’s day as Ceylon) yielded an age of 2.2 billion years, suggesting that Earth must be at least that old as well. While Boltwood was off by more than 2 billion years (Earth is now estimated to be about 4.5 billion years old), his method undergirds one of today’s best-known radiometric dating techniques.

In the Christian world, Biblical cosmology placed Earth’s age at around 6,000 years, but fossil and geology discoveries began to upend this idea in the 1700s. In 1862, physicist William Thomson, better known as Lord Kelvin, used Earth’s supposed rate of cooling and the assumption that it had started out hot and molten to estimate that it had formed between 20 and 400 million years ago. He later whittled that down to 20-40 million years, an estimate that rankled Charles Darwin and other “natural philosophers” who believed life’s evolutionary history must be much longer. “Many philosophers are not yet willing to admit that we know enough of the constitution of the universe and of the interior of our globe to speculate with safety on its past duration,” Darwin wrote. Geologists also saw this timeframe as much too short to have shaped Earth’s many layers.

Lord Kelvin and other physicists continued studies of Earth’s heat, but a new concept — radioactivity — was about to topple these pursuits. In the 1890s, Henri Becquerel discovered radioactivity, and the Curies discovered the radioactive elements radium and polonium. Still, wrote physicist Alois F. Kovarik in a 1929 biographical sketch of Boltwood, “Radioactivity at that time was not a science as yet, but merely represented a collection of new facts which showed only little connection with each other.”

February 1907: Bertram Boltwood Estimates Earth is at Least 2.2 Billion Years Old, Tess Joosse, American Physical Society

A team of physicists has discovered a new superconducting material with unique tunability for external stimuli, promising advancements in energy-efficient computing and quantum technology. This breakthrough, achieved through advanced research techniques, enables unprecedented control over superconducting properties, potentially revolutionizing large-scale industrial applications.

Topics: Applied Physics, Materials Science, Solid-State Physics, Superconductors

Researchers used the Advanced Photon Source to verify the rare characteristics of this material, potentially paving the way for more efficient large-scale computing.

As industrial computing needs grow, the size and energy consumption of the hardware needed to keep up with those needs grows as well. A possible solution to this dilemma could be found in superconducting materials, which can reduce energy consumption exponentially. Imagine cooling a giant data center full of constantly running servers down to nearly absolute zero, enabling large-scale computation with incredible energy efficiency.

Breakthrough in Superconductivity Research

Physicists at the University of Washington and the U.S. Department of Energy’s (DOE) Argonne National Laboratory have made a discovery that could help enable this more efficient future. Researchers have found a superconducting material that is uniquely sensitive to outside stimuli, enabling the superconducting properties to be enhanced or suppressed at will. This enables new opportunities for energy-efficient switchable superconducting circuits. The paper was published in Science Advances.

Superconductivity is a quantum mechanical phase of matter in which an electrical current can flow through a material with zero resistance. This leads to perfect electronic transport efficiency. Superconductors are used in the most powerful electromagnets for advanced technologies such as magnetic resonance imaging, particle accelerators, fusion reactors, and even levitating trains. Superconductors have also found uses in quantum computing.

Scientists Discover Groundbreaking Superconductor With On-Off Switches, Argonne National Laboratory

Fluorine gas etches the surface of silicon into a series of angular peaks that, when viewed with a powerful microscope, look much like the pyramid pattern in the sound-proofing foam shown above. Researchers at PPPL have now modeled how these peaks form in silicon, creating a material that is highly light absorbent. Credit: Pixabay/CC0 Public Domain

Topics: Energy, Environment, Materials Science, Nanomaterials, Solar Power

Researchers at the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL) have developed a new theoretical model explaining one way to make black silicon, an important material used in solar cells, light sensors, antibacterial surfaces, and many other applications.

Black silicon is made when the surface of regular silicon is etched to produce tiny nanoscale pits on the surface. These pits change the color of the silicon from gray to black and, critically, trap more light, an essential feature of efficient solar cells.

While there are many ways to make black silicon, including some that use the charged, fourth state of matter known as plasma, the new model focuses on a process that uses only fluorine gas. PPPL Postdoctoral Research Associate Yuri Barsukov said the choice to focus on fluorine was intentional: The team at PPPL wanted to fill a gap in publicly available research. While some papers have been published about the role of charged particles called ions in the production of black silicon, not much has been published about the role of neutral substances, such as fluorine gas.

"We now know—with great specificity—the mechanisms that cause these pits to form when fluorine gas is used," said Barsukov, one of the authors of a new paper about the work, appearing in the Journal of Vacuum Science & Technology A.

"This kind of information, published publicly and openly available, benefits us all, whether we pursue further knowledge into the basic knowledge that underlines such processes or we seek to improve manufacturing processes," Barsukov added.

How black silicon, a prized material used in solar cells, gets its dark, rough edge, Rachel Kremen, Princeton Plasma Physics Laboratory

Scientists have developed amorphous silicon carbide, a strong and scalable material with potential uses in microchip sensors, solar cells, and space exploration. This breakthrough promises significant advancements in material science and microchip technology. An artist’s impression of amorphous silicon carbide nanostrings testing to its limit tensile strength. Credit: Science Brush

Topics: Applied Physics, Chemistry, Materials Science, Nanomaterials, Semiconductor Technology

A new material that doesn’t just rival the strength of diamonds and graphene but boasts a yield strength ten times greater than Kevlar, renowned for its use in bulletproof vests.

Researchers at Delft University of Technology, led by assistant professor Richard Norte, have unveiled a remarkable new material with the potential to impact the world of material science: amorphous silicon carbide (a-SiC).

Beyond its exceptional strength, this material demonstrates mechanical properties crucial for vibration isolation on a microchip. Amorphous silicon carbide is particularly suitable for making ultra-sensitive microchip sensors.

The range of potential applications is vast, from ultra-sensitive microchip sensors and advanced solar cells to pioneering space exploration and DNA sequencing technologies. The advantages of this material’s strength, combined with its scalability, make it exceptionally promising.

Researchers at Delft University of Technology, led by assistant professor Richard Norte, have unveiled a remarkable new material with the potential to impact the world of material science: amorphous silicon carbide (a-SiC).

The researchers adopted an innovative method to test this material’s tensile strength. Instead of traditional methods that might introduce inaccuracies from how the material is anchored, they turned to microchip technology. By growing the films of amorphous silicon carbide on a silicon substrate and suspending them, they leveraged the geometry of the nanostrings to induce high tensile forces. By fabricating many such structures with increasing tensile forces, they meticulously observed the point of breakage. This microchip-based approach ensures unprecedented precision and paves the way for future material testing.

Why the focus on nanostrings? “Nanostrings are fundamental building blocks, the foundation that can be used to construct more intricate suspended structures. Demonstrating high yield strength in a nanostring translates to showcasing strength in its most elemental form.”

10x Stronger Than Kevlar: Amorphous Silicon Carbide Could Revolutionize Material Science, Delft University Of Technology

Scandium is the only known elemental superconductor to have a critical temperature in the 30 K range. This phase diagram shows the superconducting transition temperature (T_c) and crystal structure versus pressure for scandium. The measured results on all the five samples studied show consistent trends. (Courtesy: Chinese Phys. Lett. 40 107403)

Topics: Applied Physics, Chemistry, Condensed Matter Physics, Materials Science, Superconductors, Thermodynamics

Scandium remains a superconductor at temperatures above 30 K (-243.15 Celsius, -405.67 Fahrenheit), making it the first element known to superconduct at such a high temperature. The record-breaking discovery was made by researchers in China, Japan, and Canada, who subjected the element to pressures of up to 283 GPa – around 2.3 million times the atmospheric pressure at sea level.

Many materials become superconductors – that is, they conduct electricity without resistance – when cooled to low temperatures. The first superconductor to be discovered, for example, was solid mercury in 1911, and its transition temperature T_c is only a few degrees above absolute zero. Several other superconductors were discovered shortly afterward with similarly frosty values of T_c.

In the late 1950s, the Bardeen–Cooper–Schrieffer (BCS) theory explained this superconducting transition as the point at which electrons overcome their mutual electrical repulsion to form so-called “Cooper pairs” that then travel unhindered through the material. But beginning in the late 1980s, a new class of “high-temperature” superconductors emerged that could not be explained using BCS theory. These materials have Tc above the boiling point of liquid nitrogen (77 K), and they are not metals. Instead, they are insulators containing copper oxides (cuprates), and their existence suggests it might be possible to achieve superconductivity at even higher temperatures.

The search for room-temperature superconductors has been on ever since, as such materials would considerably improve the efficiency of electrical generators and transmission lines while also making common applications of superconductivity (including superconducting magnets in particle accelerators and medical devices like MRI scanners) simpler and cheaper.

Scandium breaks temperature record for elemental superconductors, Isabelle Dumé, Physics World

Researchers are working to overcome challenges related to nanoscale optoelectronic interconnects, which use light to transmit signals around an integrated circuit. IMAGE: PROVIDED BY NCNST

Topics: Biology, Materials Science, Nanoengineering, Nanomaterials, Nanotechnology, Quantum Mechanics

The promise of nanotechnology, the engineering of machines and systems at the nanoscale, is anything but tiny. Over the past decade alone, there has been an explosion in research on how to design and build components that solve problems across almost every sector, and nanotechnology innovations have led to huge advancements in our quest to address humanity’s grand challenges, from healthcare to water to food security.

Like any area of scholarship, there are still so many unknowns. And yet, there are more talented scientists and engineers endeavoring to better comprehend and harness the power of nanotechnology than ever before. The future is bright for nanotechnology and its applications.

In celebration of its 20th anniversary, the National Center for Nanoscience and Technology, China (NCNST), a subsidiary of the prestigious Chinese Academy of Sciences, partnered with Science Custom Publishing to survey nanoscience experts from the journal and across the globe about the most knotty and fascinating questions that still need to be answered if we are to advance nanotechnology in society.

The Tiny Ten: Experts weigh in on the top 10 challenges remaining for nanoscience & nanotechnology, Science Magazine

In this image, optical pulses (solitons) can be seen circling through conjoined optical tracks. (Image: Yuan, Bowers, Vahala, et al.) An animated gif is at the original link below.

Topics: Applied Physics, Astronomy, Electrical Engineering, Materials Science, Nanoengineering, Optics

(Nanowerk News) When we last checked in with Caltech's Kerry Vahala three years ago, his lab had recently reported the development of a new optical device called a turnkey frequency microcomb that has applications in digital communications, precision timekeeping, spectroscopy, and even astronomy.

This device, fabricated on a silicon wafer, takes input laser light of one frequency and converts it into an evenly spaced set of many distinct frequencies that form a train of pulses whose length can be as short as 100 femtoseconds (quadrillionths of a second). (The comb in the name comes from the frequencies being spaced like the teeth of a hair comb.)

Now Vahala, Caltech's Ted and Ginger Jenkins, Professor of Information Science and Technology and Applied Physics and executive officer for applied physics and materials science, along with members of his research group and the group of John Bowers at UC Santa Barbara, have made a breakthrough in the way the short pulses form in an important new material called ultra-low-loss silicon nitride (ULL nitride), a compound formed of silicon and nitrogen. The silicon nitride is prepared to be extremely pure and deposited in a thin film.

In principle, short-pulse microcomb devices made from this material would require very low power to operate. Unfortunately, short light pulses (called solitons) cannot be properly generated in this material because of a property called dispersion, which causes light or other electromagnetic waves to travel at different speeds, depending on their frequency. ULL has what is known as normal dispersion, and this prevents waveguides made of ULL nitride from supporting the short pulses necessary for microcomb operation.

In a paper appearing in Nature Photonics ("Soliton pulse pairs at multiple colors in normal dispersion microresonators"), the researchers discuss their development of the new micro comb, which overcomes the inherent optical limitations of ULL nitride by generating pulses in pairs. This is a significant development because ULL nitride is created with the same technology used for manufacturing computer chips. This kind of manufacturing technique means that these microcombs could one day be integrated into a wide variety of handheld devices similar in form to smartphones.

The most distinctive feature of an ordinary microcomb is a small optical loop that looks a bit like a tiny racetrack. During operation, the solitons automatically form and circulate around it.

"However, when this loop is made of ULL nitride, the dispersion destabilizes the soliton pulses," says co-author Zhiquan Yuan (MS '21), a graduate student in applied physics.

Imagine the loop as a racetrack with cars. If some cars travel faster and some travel slower, then they will spread out as they circle the track instead of staying as a tight pack. Similarly, the normal dispersion of ULL means light pulses spread out in the microcomb waveguides, and the microcomb ceases to work.

The solution devised by the team was to create multiple racetracks, pairing them up so they look a bit like a figure eight. In the middle of that '8,' the two tracks run parallel to each other with only a tiny gap between them.

Conjoined 'racetracks' make new optical devices possible, Nanowerk.

 Comparison of cathode volume changes in all-solid-state cells under low-pressure operation. Credit: Korea Institute of Science and Technology

Topics: Batteries, Chemistry, Climate Change, Lithium, Materials Science, Nanomaterials

Often referred to as the "dream batteries," all-solid-state batteries are the next generation of batteries that many battery manufacturers are competing to bring to market. Unlike lithium-ion batteries, which use a liquid electrolyte, all components, including the electrolyte, anode, and cathode, are solid, reducing the risk of explosion, and are in high demand in markets ranging from automobiles to energy storage systems (ESS).

However, devices that maintain the high pressure (10s of MPa) required for stable operation of all-solid-state batteries have problems that reduce the battery performance, such as energy density and capacity, and must be solved for commercialization.

Dr. Hun-Gi Jung and his team at the Energy Storage Research Center at the Korea Institute of Science and Technology (KIST) have identified degradation factors that cause rapid capacity degradation and shortened lifespan when operating all-solid-state batteries at pressures similar to those of lithium-ion batteries. The research is published in the journal Advanced Energy Materials.

Unlike previous studies, the researchers confirmed for the first time that degradation can occur inside the cathode as well as outside, showing that all-solid-state batteries can be operated reliably even in low-pressure environments.

In all-solid-state batteries, the cathode and anode have a volume change during repeated charging and discharging, resulting in interfacial degradation, such as side reaction and contact loss between active materials and solid electrolytes, which increase the interfacial resistance and worsen cell performance.

To solve this problem, external devices are used to maintain high pressure, but this has the disadvantage of reducing energy density as the weight and volume of the battery increase. Research is being conducted on the inside of the all-solid-state cell to maintain the performance of the cell, even in low-pressure environments.

Investigation of the degradation mechanism for all-solid-state batteries takes another step toward commercialization, National Research Council of Science and Technology.

Chromatic imaging of white light with a single lens (left) and achromatic imaging of white light with a hybrid lens (right). Credit: The Grainger College of Engineering at the University of Illinois Urbana-Champaign

Topics: 3D Printing, Additive Manufacturing, Applied Physics, Materials Science, Optics

Using 3D printing and porous silicon, researchers at the University of Illinois Urbana-Champaign have developed compact, visible wavelength achromats that are essential for miniaturized and lightweight optics. These high-performance hybrid micro-optics achieve high focusing efficiencies while minimizing volume and thickness. Further, these microlenses can be constructed into arrays to form larger area images for achromatic light-field images and displays.

This study was led by materials science and engineering professors Paul Braun and David Cahill, electrical and computer engineering professor Lynford Goddard, and former graduate student Corey Richards. The results of this research were published in Nature Communications.

"We developed a way to create structures exhibiting the functionalities of classical compound optics but in highly miniaturized thin film via non-traditional fabrication approaches," says Braun.

In many imaging applications, multiple wavelengths of light are present, e.g., white light. If a single lens is used to focus this light, different wavelengths focus at different points, resulting in a color-blurred image. To solve this problem, multiple lenses are stacked together to form an achromatic lens. "In white light imaging, if you use a single lens, you have considerable dispersion, and so each constituent color is focused at a different position. With an achromatic lens, however, all the colors focus at the same point," says Braun.

The challenge, however, is that the required stack of lens elements required to make an achromatic lens is relatively thick, which can make a classical achromatic lens unsuitable for newer, scaled-down technological platforms, such as ultracompact visible wavelength cameras, portable microscopes, and even wearable devices.

A new (micro) lens on optics: Researchers develop hybrid achromats with high focusing efficiencies,  Amber Rose, University of Illinois Grainger College of Engineering

Credit: CC0 Public Domain

Topics: Condensed Matter Physics, Materials Science, Quantum Computer, Quantum Mechanics

Quantum scientists have discovered a rare phenomenon that could hold the key to creating a 'perfect switch' in quantum devices, which flips between being an insulator and a superconductor.

The research, led by the University of Bristol and published in Science, found these two opposing electronic states exist within purple bronze, a unique one-dimensional metal composed of individual conducting chains of atoms.

Tiny changes in the material, for instance, prompted by a small stimulus like heat or light, may trigger an instant transition from an insulating state with zero conductivity to a superconductor with unlimited conductivity and vice versa. This polarized versatility, known as "emergent symmetry," has the potential to offer an ideal On/Off switch in future quantum technology developments.

Lead author Nigel Hussey, Professor of Physics at the University of Bristol, said, "It's a really exciting discovery that could provide a perfect switch for quantum devices of tomorrow.

"The remarkable journey started 13 years ago in my lab when two Ph.D. students, Xiaofeng Xu, and Nick Wakeham, measured the magnetoresistance—the change in resistance caused by a magnetic field—of purple bronze."

In the absence of a magnetic field, the resistance of purple bronze was highly dependent on the direction in which the electrical current was introduced. Its temperature dependence was also rather complicated. Around room temperature, the resistance is metallic, but as the temperature is lowered, this reverses and the material appears to be turning into an insulator. Then, at the lowest temperatures, the resistance plummets again as it transitions into a superconductor.

Despite this complexity, surprisingly, the magnetoresistance was found to be extremely simple. It was essentially the same irrespective of the direction in which the current or field was aligned and followed a perfect linear temperature dependence all the way from room temperature down to the superconducting transition temperature.

Research reveals rare metal could offer revolutionary switch for future quantum devices, Queen's University Belfast, Phys.org.

That isn't tea, but the paradox still applies: Dispersing gold nanoparticles in an aqueous chlorine solution. (Courtesy: Ai Du)

Topics: Aerogels, Einstein, Materials Science, Nanomaterials, Soft Materials

If you stir a colloidal solution containing nanoparticles, you might expect the particles to disperse evenly through the liquid. But that’s not what happens. Instead, the particles end up concentrated in a specific region and may even clump together. This unexpected result is an example of Einstein’s tea leaf paradox, and the researchers at Tongji University in China who discovered it – quite by accident – say it could be used to collect particles or molecules for detection in a dilute solution. Importantly, it could also be used to make aerogels for technological applications.

We usually stir a liquid to evenly disperse the substances in it. The phenomenon known as Einstein’s tea leaf paradox describes a reverse effect in which the leaves in a well-stirred cup of tea instead become concentrated in a doughnut-shaped area and gather at the bottom center of the cup once stirring ceases. While this paradox has been known about for more than 100 years and is understood to be caused by a secondary flow effect, there are few studies on how it manifests for nanoparticles in a stirred solution.

Liquid "squeezing"

Researchers led by Ai Du of the School of Physics, Science, and Engineering at Tongji University in Shanghai have now simulated how gold nanoparticle spheres dispersed in water move when the solution is stirred. When they calculated the flow velocity distribution of the fluid, they found that the rate at which the particles moved appeared to follow the fluid’s flow velocity.

“Interestingly, by dividing the whole container into several sectors, we also observed that the high-velocity region driven by the stirrer was also the region in which the particles aggregated,” explains Du. “We think that this phenomenon is probably due to direct ‘squeezing’ of the liquid created by the stirrer and comes from the mass differences between the nanoparticles and the liquid phase.”

Einstein’s tea leaf paradox could help make aerogels, Isabelle Dumé, Physics World.

Researchers from the University of Connecticut and colleagues have created a highly durable, lightweight material by structuring DNA and then coating it in glass. The resulting product, characterized by its nanolattice structure, exhibits a unique combination of strength and low density, making it potentially useful in applications like vehicle manufacturing and body armor. (Artist’s concept.)

Topics: Biotechnology, DNA, Material Science, Nanomaterials

Researchers have developed a highly robust material with an extremely low density by constructing a structure using DNA and subsequently coating it in glass.

Materials possessing both strength and lightness have the potential to enhance everything from automobiles to body armor. But usually, the two qualities are mutually exclusive. However, researchers at the University of Connecticut, along with their collaborators, have now crafted an incredibly strong yet lightweight material. Surprisingly, they achieved this using two unexpected building blocks: DNA and glass.

“For the given density, our material is the strongest known,” says Seok-Woo Lee, a materials scientist at UConn. Lee and colleagues from UConn, Columbia University, and Brookhaven National Lab reported the details on July 19 in Cell Reports Physical Science.

Strength is relative. Iron, for example, can take 7 tons of pressure per square centimeter. But it’s also very dense and heavy, weighing 7.8 grams/cubic centimeter. Other metals, such as titanium, are stronger and lighter than iron. And certain alloys combining multiple elements are even stronger. Strong, lightweight materials have allowed for lightweight body armor and better medical devices and made safer, faster cars and airplanes.

Scientists Create New Material Five Times Lighter and Four Times Stronger Than Steel. Sci-Tech Daily

Reference: “High-strength, lightweight nano-architected silica” by Aaron Michelson, Tyler J. Flanagan, Seok-Woo Lee, and Oleg Gang, 27 June 2023, Cell Reports Physical Science.
DOI: 10.1016/j.xcrp.2023.101475

Electric field- and pressure-assisted fast sintering to control graphene alignment in thick composite electrodes for boosting lithium storage performance. Credit: Hongtao Sun, Penn State

Topics: Battery, Energy, Graphene, Green Tech, Lithium, Materials Science, Nanomaterials

The demand for high-performance batteries, especially for use in electric vehicles, is surging as the world shifts its energy consumption to a more electric-powered system, reducing reliance on fossil fuels and prioritizing climate remediation efforts. To improve battery performance and production, Penn State researchers and collaborators have developed a new fabrication approach that could make for more efficient batteries that maintain energy and power levels.

The improved method for fabricating battery electrodes may lead to high-performance batteries that would enable more energy-efficient electric vehicles, as well as such benefits as enhancing power grid storage, according to Hongtao Sun. Sun is an assistant professor of industrial and manufacturing engineering at Penn State and the co-corresponding author of the study, which was published in and featured on the front cover of Carbon.

"With current batteries, we want them to enable us to drive a car for longer distances, and we want to charge the car in maybe five minutes, 10 minutes, comparable to the time it takes to fill up for gas," Sun said. "In our work, we considered how we can achieve this by making the electrodes and battery cells more compact, with a higher percentage of active components and a lower percentage of passive components."

If an electric car maker wants to improve the driving distance of their vehicles, they add more battery cells, numbering in the thousands. The smaller and lighter, the better, according to Sun.

"The solution for longer driving distances for an electric vehicle is just to add compact batteries, but with denser and thicker electrodes," Sun said, explaining that such electrodes could better connect and power the battery's components, making them more active. "Although this approach may slightly reduce battery performance per electrode weight, it significantly enhances the vehicle's overall performance by reducing the battery package's weight and the energy required to move the electric vehicle."

Thicker, denser, better: New electrodes may hold the key to advanced batteries, Jamie Oberdick, Pennsylvania State University, techxplore.

The central role of HFIP: a solvent component that solvates POM. a. 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP): an effective solvent for polyoxymethylene (POM), the clustering of HFIP enabled the decrease of σ*OH energy38. b. Images of an undivided cell before (left) and after (right) the electrolysis. c. Reaction profile of POM bulk electrolysis at 3.5 V (60 °C), 0.1 M LiClO4 in CH3CN: HFIP (26:4). Credit: Nature Communications (2023). DOI: 10.1038/s41467-023-39362-z

Topics: Chemistry, Green Tech, Materials Science, Star Trek

A group of researchers at the University of Illinois Urbana-Champaign demonstrated a way to use the renewable energy source of electricity to recycle a form of plastic that's growing in use but more challenging to recycle than other popular forms of plastic.

In their study recently published in Nature Communications, they share their innovative process that shows the potential for harnessing renewable energy sources in the shift toward a circular plastics economy.

"We wanted to demonstrate this concept of bringing together renewable energy and a circular plastic economy," said Yuting Zhou, a postdoctoral associate, and co-author, who worked on this groundbreaking research with two professors in chemistry at Illinois, polymer expert Jeffrey Moore and electrochemistry expert Joaquín Rodríguez-López.

The project was conceived by Moore, who had experience working with Poly(phthalaldehyde), a form of polyacetal. Polyoxymethylene (POM) is a high-performance acetal resin that is used in a variety of industries, including automobiles and electronics. A thermoplastic, it can be shaped and molded when heated and hardens upon cooling with a high degree of strength and rigidity, making it an attractive lighter alternative to metal in some applications, like mechanical gears in automobiles. It is produced by various chemical firms with slightly different formulas and names, including Delrin by DuPont.

When recycling, those highly crystalline properties of POM make it difficult to break down. It can be melted and molded again, but POM's original material properties are lost, limiting the usefulness of the recycled material.

"When the polymer was in use as a product, it was not a pure polymer. It will also have other chemicals like coloring additives and antioxidants. So, if you simply melt it and remold it, the material properties are always lost," Zhou explained.

The Illinois research team's method uses electricity, which can be drawn from renewable sources, and takes place at room temperature.

This electro-mediated process deconstructs the polymer, breaking it down into monomers—the molecules that are bonded to other identical molecules to form polymers.

A recycling study demonstrates new possibilities for a circular plastics economy powered by renewable energy, Tracy Crane, University of Illinois at Urbana-Champaign.

Credit: Freddie Pagani for Physics Today

Topics: African Americans, Diversity in Science, Electrical Engineering, Materials Science, Physics

Students should strategically consider where to apply to graduate school, and faculty members should provide up-to-date job resources so that undergraduates can make informed career decisions.

The number of bachelor’s degrees in physics awarded annually at US institutions is at or near an all-time high—nearly double what it was two decades ago. Yet the number of first-year physics graduate students has grown much more slowly, at only around 1–2% per year. The difference in the growth rates of bachelor’s recipients and graduate spots may be increasing the competition that students face when interested in pursuing graduate study.

With potentially more students applying for a relatively fixed number of first-year graduate openings, students may need to apply to more schools, which would take more time and cost more money. As the graduate school admissions process becomes more competitive, applicants may need even more accomplishments and experiences, such as postbaccalaureate research, to gain acceptance. Such opportunities are not available equally to all students. To read about steps one department has taken to make admissions more equitable, see the July Physics Today article by one of us (Young), Kirsten Tollefson, and Marcos D. Caballero.

We do not view the increasing gap between bachelor’s recipients and graduate spots as necessarily a problem, nor do we believe that all physics majors should be expected to go to graduate school. Rather, we assert that this trend is one that both prospective applicants and those advising them should be aware of so students can make an informed decision about their postgraduation plans.

The “itch” for graduate school has always been a constant with me. I wanted especially to go after meeting Dr. Ronald McNair after his maiden voyage on Challenger in 1984. Little did I know that he would perish two years later in the same vehicle. Things happened to set the itch aside: marriage, kids, sports leagues. Life can delay your decision, too. My gap was 33 years: 1984 to 2017.

The recent decision by the Supreme Court to overturn another precedent: Affirmative Action in college admissions, affects graduate schools as well as undergraduate admissions. After every effort of progress, whether in race (a social construct) relations, labor, or gender, history, if they allow us to study it, has always shown a backlash. The group that is in power wants to remain in power, and the inequity those of us lower on the totem poll are pointing out they see as the result of the "natural order," albeit by government fiat.

My pastor at the time could have called our congressman and gotten me an appointment. My grades weren't too bad, and being the highest-ranking cadet in the city and county probably would have helped my CV. I chose an HBCU, NC A&T State University, in my undergrad because Greensboro to Winston-Salem was and is a lot closer than the Air Force Academy in Colorado. I would have been away from my parents for an entire agonizing year of no contact: cell phones and video chatting weren't a thing. I also wasn’t a fan of my freshman year being called a “Plebe” (lower-born). I do support the decisions students and their parents make as the best decision for their future. I do not support an unelected body trying to do "reverse political Entropy," turning back the clock of progress to 1953. We are, however, in 2023, and issues like climate change can be solved by going aggressively towards renewables: Texas experienced some of the hottest days on the planet, and their off-the-national grid held because of solar and wind, in an impressive display of irony.

Physics majors who graduate and go to work are prepared for either teaching K-12 or engineering. I worked at Motorola, Advanced Micro Devices, and Applied Materials. I taught Algebra 1, Precalculus, and Physics. So, if it’s any consolation: physics majors will EARN a living and eat! As a generalist, you should be able to master anything you’d be exposed to.

Speaking of Harvard: when I worked at Motorola in Austin, Texas, one of my coworkers was promoted from process engineering to Section Manager of Implant/Diffusion/Thin Films. He attended Harvard, and I, A&T. I still worked in photo and etch, primarily as the etch process engineer on nights. I noticed he had a familiar green book on his bookshelf with yellow, sinusoidal lines on the cover.

Me: Hey! Isn't that a Halladay and Resnick?

Him: Why, yes! What do you know about it?

Me: I learned Physics I from Dr. Tom Sandin (who recently retired after 50 YEARS: 1968 - 2018). He taught Dr. Ron McNair, one of the astronauts on the Space Shuttle Challenger. Physics II was taught to me by Dr. Elvira Williams: she was the first African American woman to earn a Ph.D. in Physics in the state of North Carolina and the FOURTH to earn a Ph.D. in Theoretical Physics in the nation. Who were your professors?

Him: Look at the time! Got a meeting. Bye!

Life experiences, in the end, overcome legacy and connection. We need a diversity of opinions to solve complex problems. Depending on the same structures and constructs to produce our next innovators isn't just shortsighted: it's magical thinking.

I now do think that 18 might be a little too young for a freshman on any campus and 22 a little too early for graduate school.

Just make the gap a little less than three decades!

The gap between physics bachelor’s recipients and grad school spots is growing, Nicholas T. Young, Caitlin Hayward, and Eric F. Bell, AIP Publishing, Physics Today.