Daily Archives: August 28, 2021

Particles in many places at once, spooky influences and cats that are dead and alive at the same time these are the phenomena that earned quantum theory its reputation for weirdness

By Richard Webb

Skizzomat

THE pleasure and pain of quantum theory began when an or became an and. Are the fundamental components of material reality the things that make up light, matter, heat and so on particles or waves? The answer came back from quantum theory loud and clear: both. At the same time.

Max Planck started the rot back in 1900, when he assumed, purely to make the maths work, that the electromagnetic radiation emitted by a perfectly absorbing black body comes in the form of discrete packets of energy, or quanta. In 1905, Albert Einstein took that idea and ran with it. In his Nobel-prizewinning work on the photoelectric effect, he assumed that quanta were real, and all electromagnetic waves, light included, also act like discrete particle-like entities called photons. Work in the 1920s then reversed the logic. Discrete, point-like particles such as electrons also come with a wavelength, and sometimes act like waves.

Physicist Richard Feynman called this wave-particle duality the only mystery of quantum physics the one from which all the others flow. You cant explain it in the sense of saying how it works, he wrote; you can only say how it appears to work.

How it appears to work is often illustrated by the classic double-slit experiment. You fire a stream of single photons (or electrons, or any object obeying quantum rules) at two narrow slits close together. Place a measuring device at either of the two slits and you will see blips of individual photons with distinct positions passing through. But place a screen behind the slits and, over time, you will see a pattern of light

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This is what makes the quantum world so strange and confusing - New Scientist

Perhaps the most important property of a material is its fundamental band gap. This is the energy difference between adding and subtracting one electron from a system. It distinguishes metals from insulators and gives us information about the electronic response of the material to external influences. This is crucial in myriad technological applications like batteries, semiconductors, alloys, electronic devices, and photovoltaic materials, to name a few. Band gap predictions employing quantum simulations have steadily progressed over the years, but an accurate method valid across the broad spectrum of materials with diverse band gaps was lacking. Wing et al. (1) take a decisive step forward in the first-principles prediction of fundamental band gaps with accuracy rivaling experimental error bars in their measurement, a feat that builds upon the contributions of multiple research groups during the last few decades.

For many years, the workhorse of computational materials modeling has been density functional theory (DFT), particularly for properties like band gaps where quantum effects are preponderant. DFT is a relatively simple model whose roots precede the formulation of quantum mechanics (2). It essentially describes electrons as independent particles interacting via an effective potential obtainable from an exchange-correlation energy functional of the electron density. Somewhat paradoxically, the existence of this functional can be easily proven, but its practical realization has turned out to be much more challenging than perhaps originally envisioned. For several decades, researchers have systematically improved the accuracy of DFT, making it a valuable aid for chemistry, physics, and materials science. However, across the broad range of solid-state materials, the fundamental band gap has remained stubbornly difficult to predict with high accuracy. The form of DFT most appropriate to calculate band gaps is known as generalized KohnSham theory (3), a model where the functional depends on all the orbitals that electrons can

1Email: guscus{at}rice.edu.

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Advancing solid-state band gap predictions - pnas.org

Artists illustration of ghost particles moving through a quantum spin liquid. Credit: Jenny Nuss/Berkeley Lab

An unexpected finding by scientists at Berkeley Lab and UC Berkeley could advance quantum computers and high-temperature superconductors.

Scientists have taken the clearest picture yet of electronic particles that make up a mysterious magnetic state called a quantum spin liquid (QSL).

The achievement could facilitate the development of superfast quantum computers and energy-efficient superconductors.

The scientists are the first to capture an image of how electrons in a QSL decompose into spin-like particles called spinons and charge-like particles called chargons.

Artists illustration of ghost particles moving through a quantum spin liquid. Credit: Jenny Nuss/Berkeley Lab

Other studies have seen various footprints of this phenomenon, but we have an actual picture of the state in which the spinon lives. This is something new, said study leader Mike Crommie, a senior faculty scientist at Lawrence Berkeley National Laboratory (Berkeley Lab) and physics professor at UC.

Spinons are like ghost particles. They are like the Big Foot of quantum physics people say that theyve seen them, but its hard to prove that they exist, said co-author Sung-Kwan Mo, a staff scientist at Berkeley Labs Advanced Light Source. With our method weve provided some of the best evidence to date.

In a QSL, spinons freely move about carrying heat and spin but no electrical charge. To detect them, most researchers have relied on techniques that look for their heat signatures.

Now, as reported in the journal Nature Physics, Crommie, Mo, and their research teams have demonstrated how to characterize spinons in QSLs by directly imaging how they are distributed in a material.

Schematic of the triangular spin lattice and star-of-David charge density wave pattern in a monolayer of tantalum diselenide. Each star consists of 13 tantalum atoms. Localized spins are represented by a blue arrow at the star center. The wavefunction of the localized electrons is represented by gray shading. Credit: Mike Crommie et al./Berkeley Lab

To begin the study, Mos group at Berkeley Labs Advanced Light Source (ALS) grew single-layer samples of tantalum diselenide (1T-TaSe2) that are only three-atoms thick. This material is part of a class of materials called transition metal dichalcogenides (TMDCs). The researchers in Mos team are experts in molecular beam epitaxy, a technique for synthesizing atomically thin TMDC crystals from their constituent elements.

Mos team then characterized the thin films through angle-resolved photoemission spectroscopy, a technique that uses X-rays generated at the ALS.

Scanning tunneling microscopy image of a tantalum diselenide sample that is just 3 atoms thick. Credit: Mike Crommie et al./Berkeley Lab

Using a microscopy technique called scanning tunneling microscopy (STM), researchers in the Crommie lab including co-first authors Wei Ruan, a postdoctoral fellow at the time, and Yi Chen, then a UC Berkeley graduate student injected electrons from a metal needle into the tantalum diselenide TMDC sample.

Images gathered by scanning tunneling spectroscopy (STS) an imaging technique that measures how particles arrange themselves at a particular energy revealed something quite unexpected: a layer of mysterious waves having wavelengths larger than one nanometer (1 billionth of a meter) blanketing the materials surface.

The long wavelengths we saw didnt correspond to any known behavior of the crystal, Crommie said. We scratched our heads for a long time. What could cause such long wavelength modulations in the crystal? We ruled out the conventional explanations one by one. Little did we know that this was the signature of spinon ghost particles.

With help from a theoretical collaborator at MIT, the researchers realized that when an electron is injected into a QSL from the tip of an STM, it breaks apart into two different particles inside the QSL spinons (also known as ghost particles) and chargons. This is due to the peculiar way in which spin and charge in a QSL collectively interact with each other. The spinon ghost particles end up separately carrying the spin while the chargons separately bear the electrical charge.

Illustration of an electron breaking apart into spinon ghost particles and chargons inside a quantum spin liquid. Credit: Mike Crommie et al./Berkeley Lab

In the current study, STM/STS images show that the chargons freeze in place, forming what scientists call a star-of-David charge-density-wave. Meanwhile, the spinons undergo an out-of-body experience as they separate from the immobilized chargons and move freely through the material, Crommie said. This is unusual since in a conventional material, electrons carry both the spin and charge combined into one particle as they move about, he explained. They dont usually break apart in this funny way.

Crommie added that QSLs might one day form the basis of robust quantum bits (qubits) used for quantum computing. In conventional computing a bit encodes information either as a zero or a one, but a qubit can hold both zero and one at the same time, thus potentially speeding up certain types of calculations. Understanding how spinons and chargons behave in QSLs could help advance research in this area of next-gen computing.

Another motivation for understanding the inner workings of QSLs is that they have been predicted to be a precursor to exotic superconductivity. Crommie plans to test that prediction with Mos help at the ALS.

Part of the beauty of this topic is that all the complex interactions within a QSL somehow combine to form a simple ghost particle that just bounces around inside the crystal, he said. Seeing this behavior was pretty surprising, especially since we werent even looking for it.

Reference: Evidence for quantum spin liquid behaviour in single-layer 1T-TaSe2 from scanning tunnelling microscopy by Wei Ruan, Yi Chen, Shujie Tang, Jinwoong Hwang, Hsin-Zon Tsai, Ryan L. Lee, Meng Wu, Hyejin Ryu, Salman Kahn, Franklin Liou, Caihong Jia, Andrew Aikawa, Choongyu Hwang, Feng Wang, Yongseong Choi, Steven G. Louie, Patrick A. Lee, Zhi-Xun Shen, Sung-Kwan Mo & Michael F. Crommie, 19 August 2021, Nature Physics.DOI: 10.1038/s41567-021-01321-0

Researchers from SLAC National Accelerator Laboratory; Stanford University; Argonne National Laboratory; the Massachusetts Institute of Technology; the Chinese Academy of Sciences, Shanghai Tech University, Shenzhen University, Henan University of China; and the Korea Institute of Science and Technology and Pusan National University of Korea contributed to this study. (Co-first author Wei Ruan is now an assistant professor of physics at Fudan University in China; co-first author Yi Chen is currently a postdoctoral fellow at the Center for Quantum Nanoscience, Institute for Basic Science of Korea.)

This work was supported by the DOE Office of Science, and used resources at Berkeley Labs Advanced Light Source and Argonne National Laboratorys Advanced Photon Source. The Advanced Light Source and Advanced Photon Source are DOE Office of Science user facilities.

Additional support was provided by the National Science Foundation.

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This Exotic Particle Had an Out-of-Body Experience These Surprised Scientists Took a Picture of It - SciTechDaily

Josie Ford

Could we grow endangered plants on other planets? We pause and consider this question. No.

Still, since this query is the subject line of a PR email from an online flower-delivery service, handed to us by a colleague with a pair of tongs and a disparaging look, we find it worthy of further consideration. Even more so since we are promised conclusions reached using research and working with a designer.

Today, nearly 40% of the worlds plants are endangered, according to a report from the Royal Botanic Gardens, Kew, we read. Sad, sad science fact. But never fear, once we have destroyed Earths ecosystems, a bright, green future exists elsewhere in the solar system, at least in the world of whirly-eyed PR.

As the soil on Mars has double the amount of iron than soil on planet earth, leafy green vegetables and microgreens would easily thrive there, we learn. Dandelions, too, apparently a species far from endangered on Feedbacks small patch of terra firma. Hops vine [sic], trees, shrubs and poison ivy might be able to survive the challenging temperatures on this moon, it opines of Jupiters satellite Europa, where days struggle to rise above -135C and surface radiation levels are around 2000 times those on Earth. One of the only things that can kill poison ivy is boiling water so the cold and wet conditions on Europa seem to be the ideal environment for this plant.

The outlook is even rosier on Titan, the Saturnian moon where water ice at around -180C fulfils the function of bedrock, and great surface lakes are filled with liquid natural gas. Titans surface is sculpted by methane and ethane, which only one other planet in the solar system has: Earth. Therefore, tobacco plants should grow on this moon too, our correspondent concludes, non-sequentially.

Please let me know if you have any questions, the email ends. So, so many, including where we get some of the wacky Europa baccy too. Optimism is a fine, fine thing, but as far as the future of life on Earth is concerned, we fear the rationalists counterstatement applies: il faut cultiver notre jardin.

We are all in the gutter, but some of us are looking at the stars, as one of the usual suspects once wrote. Or we are all in the gutter, sending in responses to our recent item on peculiar toilet signage (31 July).

Toilets and viewing area was an unfortunate juxtaposition that confronted Richard Ellam at an Aberdeen Science Festival some years back, while Chris Evans relays that A lay-by eatery near where I live (on the A59 between Skipton and Clitheroe) for some years displayed a sign reading Sit-in or take-away toilet' neither of which seems particularly practicable or desirable.

Our item on the newly introduced crocodile hazard at the Royal Port Moresby Golf Club in Papua New Guinea (14 August) reminds Stuart Reeves in Wake Forest, North Carolina, of playing at the Skukuza Golf Club in Kruger National Park in South Africa a sentence that exhausts us even typing it.

Its local rules include such gems as Burrowing animals Rough/Fairway drop without penalty from holes made by burrowing animals and termites, NOT HOOF MARKS. Burrowing animals include warthogs, moles and termites.

Other rules (formal and informal) that Stuart has encountered on his travels include Give way to a herdsman and his cows crossing the fairway; free drop from a hippopotamus footprint; free drop about 3 club lengths if the ball lands in the coils of a snake (no need to be precise); if a monkey steals your ball it is a lost ball. Strong stuff and further congratulations on your self-confessed status as a recovering golfer.

Mentions in Almost the last word (14 August) of interesting numbers, numbers with their own Wiki page and the fine-structure constant (approximately 1/137) prompted me to recheck the Wiki page for 137, writes Mike Sargent, displaying the talent for the tangent that we so admire among Feedback readers. It has for several years now informed us that Wolfgang Pauli, a pioneer of quantum physics, died in a hospital room numbered 137, a coincidence that disturbed him.

It is difficult to know which is more surprising, that Paulis consciousness transcended death, or that he then contrived to communicate his feelings on his demise to a Wiki page editor, he continues. We dont wish to sound too woo, but it is a fundamental tenet of quantum mechanics that information cannot be destroyed, and Physics might create a backdoor to an afterlife but dont bank on it is the headline of an article we see in our webspace starting from that basis. We would say thats living proof, but thats possibly not quite right.

Casting our all-seeing eye over our shoulder, we see that our neighbours and friends in Almost the last word (backwards readers: youll find it towards the front) are discussing how a photon knows to travel at the speed of light.

With the privilege of having the actual last word, we must give the obvious missing answer: because it is very bright.

Got a story for Feedback?Send it to feedback@newscientist.com or New Scientist, Northcliffe House, 2 Derry Street, London W8 5TTConsideration of items sent in the post will be delayed

You can send stories to Feedback by email at feedback@newscientist.com. Please include your home address. This weeks and past Feedbacks can be seen on our website.

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Could we grow endangered plants on other planets? No - New Scientist News

ABC NewsGypsy Willis speaks to ABC News about her relationship with Dr. Martin MacNeill.

Gypsy Willis was the mistress of Dr. Martin MacNeill in an affair uncovered by his daughter, Alexis Somers. A jury convicted Martin MacNeill of murder in the death of his wife, Michele MacNeill.

Investigators initially believed the death of Michele MacNeill in 2007 was due to a heart condition, but further investigation revealed he was carrying on an affair with Willis. He submitted documents claiming they were married on the day of his wifes funeral, according to the Salt Lake Tribune. His daughters fought for justice in the case, and he was convicted of murder and obstruction of justice in 2013. Willis was sentenced to time in prison for identity theft, according to ABC News.

ABC 20/20 is revisiting the case in an encore episode, The Perfect Nanny. It airs Friday, August 27, 2021 at 9 p.m. Eastern time.

Heres what you need to know:

Alexis Somers, the daughter of Martin and Michele MacNeill, logged into her fathers phone and printed out his phone records soon before her mothers death, Somers told ABC News. Her mother was suspicious of her husbands behavior, and Somers checked his phone while he slept. She said she found he had multiple phone calls with Gypsy Jillian Willis.

The first time Somers heard her dad refer to the woman was on the day of her mothers funeral.

He said Oh, I found the perfect nanny. And I said, Whats her name? And he said, Oh, I think its, I think its Jillian? And I said Dad? Gypsy Jillian Willis? Somers remembered. I said, I know that woman. I know mom was worried you were having an affair with her and you are not to bring her in the home.

Willis told City Weekly she saw Martin MacNeill in court in 2012 for the first time since 2009. She said he appeared much older and thinner.

I would look at him and remember our life together. I dont think anyone could do that and not feel something, she said. Most of it is just sorrow that it didnt work, that people were hurt, that we were in these circumstances. But I loved Martin, and I dont think that was a bad thing.

Willis told ABC News about the beginning of her relationship with Martin MacNeill. She said the two met online, and that she knew he was married.

We met online. He sent me a message, Willis told ABC News in 2013. He asked me what I knew about quantum physics There was just instant chemistry. He was tall, he was handsome, he was very well spoken.

She said she wasnt looking for anything serious, so she was unconcerned about his marriage.

He told me that he had a perfect life. That he had a perfect wife, she told ABC News.

A Facebook page listing Willis full name says she is living in Salt Lake City, Utah. The page is largely private, but it lists a series of her favorite quotes.

One says, Mistakes are like bad loves, the more you learn from them, the more you wish theyd never happened.

READ NEXT: Alexis Somers Today: Michele MacNeills Daughter Now

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Gyspsy Willis Today: Where Is She Now in 2021? - Heavy.com