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The 10 quirkiest stories from the world of physics in 2022

From the physics of the perfect burger to a board game inspired by a synchrotron, physics has had its fair share of quirky stories this year. Here is our pick of the best 10, in no particular order.

Diamond: the game

Synchrotrons and some board games have at least one aspect in common: they involve things going round in a circle. Mark Basham and Claire Murray from the UK’s Diamond Light Source synchrotron and Matthew Dunstan at the University of Cambridge saw the parallels and created “Diamond: the Game”. Suitable for anyone aged 10 and over, the game – which takes no more than half an hour to complete – puts players in the role of a researcher at Diamond. By visiting different beamlines while progressing round the board, participants learn about the diversity of science that is done at the facility – including physics, chemistry, cultural heritage and more. The game has been tested by more than 200 students and was released online as a free-to-print game in 2020. Since then, Diamond has been played by more than 14,000 players in more than 30 countries worldwide. Whether it makes being stuck on the beamline at 2 a.m. more bearable is open to question.

In the doghouse

The auction house Christie’s held its annual sale of rare and unusual meteorites in late February. The 66 lots included a 15 g fragment of the Winchcombe meteorite, which in 2021 became the UK’s most coveted rock after it was seen across the sky over the Cotswold town. It sold for a cool $30,240 while a smaller 1.7 g fragment fetched $12,600. Another item under the hammer was a meteorite that in April 2019 created an 18 cm hole in the oxidized tin roof of a doghouse in Aguas Zarcas, Costa Rica. Its resident, a German shepherd named Roky, survived unharmed. The kennel-striking meteorite, which is 70% covered with “fusion crust”, had a guide price of $40,000–60,000 but in the end went for a disappointing £21,240. But that wasn’t the most unusual item. “Lot 4” was the doghouse itself, placed on some artificial grass together with an orange dog bowl. The lot had a guide price of $300,000, and though it went for a paltry $44,100, that’s still probably enough to buy Roky a nice new home.

Here’s your chance of love

In late 2020 physicist Steven Wooding created an online resource to persuade “flat-Earthers” that the Earth is spherical and not a disc. Wooding was back this year with a new project about something just as tricky – finding your chances of love. Released just before Valentine’s Day, the Drake Equation for Love Calculator is an adaptation of the famous Drake equation, which estimates the number of alien civilizations in our galaxy with whom we could communicate. The love calculator – created with the help of data scientist Rijk de Wet – asks users to input their location, social skills and attractiveness as well as the age range of potential partners and whether they are university educated. The output is then compared to the possibility of an alien civilization existing within 1000 light-years of the Earth. Wooding told Physics World that his own odds of finding love are 2.1 times better than the possibility of alien life. Is he being perhaps a bit picky?

Jurassic race

Could the Jamaican sprinter Usain Bolt have beaten a 400 kg dinosaur in a 100 m sprint? It’s probably not a question you’ve wondered about before, but Scott Lee, a physicist from the University of Toledo in Ohio, thought it would be a good problem for his students to solve. To make it a fair race, Lee choose the theropod dinosaur Dilophosaurus wetherilli as it’s thought to have had a top running speed of about 10 m/s, which is just a shade over Bolt’s 9.58 s world record that he set in the 100 m sprint at the 2009 World Athletics Championships in Berlin. Using concepts from 1D kinematics and numerical techniques, the students discovered that Bolt’s acceleration at the start would leave the Dilophosaurus in the dust, with the legendary sprinter winning the race with a good two seconds to spare. Given that the Dilophosaurus had razor-sharp claws and the ability to spit venom at its pray (as DNA thief Dennis Nedry discovered in the film Jurassic Park), we imagine Bolt – in any hypothetical race – would have plenty of motivation to smash his own record.

SEM image of a tardigrade — Quantum life: an electron microscope image of a tardigrade. (Courtesy: Elham Schokraie *et al.*/*PLOS ONE* 7(9): e45682/CC BY 2.5)

Entangled tale

Imagine being able to survive when chilled to near absolute zero. That’s what tiny organisms called tardigrades can do, but could these cute-looking “water bears” have another low-temperature trick up their sleeve? To find out, an international team of physicists chilled a tardigrade to below 10 mK and then used it as the dielectric in a capacitor that itself was part of a superconducting transmon qubit. The researchers then entangled the qubit – tardigrade and all – with another superconducting qubit before warming up the tardigrade and bringing it out of its latent state of life called cryptobiosis. Some physicists, however, remain unconvinced. “This is not entanglement in any meaningful sense,” Rice University physicist Douglas Natelson noted on his blog. Whether or not the researchers achieved quantum entanglement, they definitely did set a record for the extreme conditions that a complex lifeform can survive, with the tardigrade spending 420 hours at temperatures below 10 mK and pressures of 6 × 10⁻⁶ mbar.

Keeping a lid on it

Closing the lid on your favourite board game box can take a while as it slides down the base to close. This so-called “telescoping” cardboard box – where the lid barely overlaps with the base – is commonly used to hold or ship a variety of objects from board games and footwear to mobile phones. Such boxes are cheap to make and while the economic and environmental aspects have been well studied, the physics never had. To make amends, Jolet de Ruiter from Wageningen University and colleagues carried out experiments on commercially available boxes and 3D printed models to investigate the fluid dynamics of the sliding box lid. The researchers used low-Reynolds-number fluid flow to derive a theory for the flow of a thin film of air in the gap between the lid and base. They then compared this to experiments to find that the fastest way for the box lid to close is not based on a conventional straight lid-base configuration but for the lid to have a slight angle – just a few degrees – relative to the vertical base. If this design ever hits the shelves, we can thank the researchers for thinking outside the box.

Let’s do the twist

When it comes to eating an Oreo, some of us can’t resist twisting the two biscuits apart and licking the filling off. That’s because most – if not all – of the filling ends up stuck on one biscuit or the other. Crystal Owens, a PhD student at the Massachusetts Institute of Technology, tackled the physics of how that mysterious separation occurs. She and her colleagues created an “oerometer” – a rheometer that grasps the two biscuits and gives the cookie a twist until it separates into two. They confirmed that the filling always ends up on one biscuit, suggesting the effect doesn’t depend on precisely how an Oreo is twisted. The amount of filling doesn’t affect the separation process either, although what does make a difference is the twisting speed, with a slow twist being better for a clean break. Unfortunately, the research doesn’t explain why the filling always ends up on one side, though Owens reckons it could be linked to how Oreos are manufactured. Yeah, but what about custard creams?

Champagne cork popping — Supersonic: gases escape very quickly from a champagne bottle. (Courtesy: Shutterstock/Lukas Gojda)

Fizz goes supersonic

Opening a bottle of good champagne is one of life’s great delights and it is also a process that involves a lot of physics. Gérard Liger-Belair from Université de Reims Champagne-Ardenne and colleagues studied the uncorking process in more detail, in particular what happens in the few milliseconds after a bottle has been opened. In 2019 research by the group showed, for the first time, the formation of shock waves in the fluid during cork popping. Building on that work, the team found that a succession of normal and oblique shock waves combines to form “shock diamonds” – patterns of rings typically seen in rocket exhaust plumes. It results in the gas mixture escaping from the bottle at supersonic speeds. “Our paper unravels the unexpected and beautiful flow patterns that are hidden right under our nose each time a bottle of bubbly is uncorked,” says Liger-Belair. “Who could have imagined the complex and aesthetic phenomena hidden behind such a common situation experienced by any one of us?” We’ll raise a glass to that.

The physics of the perfect burger

What is the most effective way to grill a burger or a steak – flip the meat once or many times? Some chefs think you should flip only once as doing so multiple times will mean less browning and therefore less flavour. Others, however, claim that regular flipping results in a more even cook and is also about 30% faster, given that each surface of the meat is exposed to heat relatively evenly and has less time to cool down. Mathematician Jean-Luc Thiffeault from the University of Wisconsin in the US created a “simple” model to demonstrate this speedy cooking time for flipped meat. Assuming a burger is an infinite thin slab and has symmetric thermal properties – i.e. the same at the top and the bottom – he used a 1D heat equation to find that flipping the patty once results in a final cooking time of about 80 seconds. This falls for every subsequent flip so that 20 flips results in a 20% drop in cooking time. Taking Thiffeault’s model to its mathematical extreme, a burger could cook in 63 seconds – if you flipped it infinitely many times. That would challenge even the most experienced grillers.

Follow ewe, follow me

What do the murmuration of starlings, the motion of micro-organisms, and the stopping and starting of traffic on a busy motorway have in common? They’re all examples of collective motion studied by physicists – and now you can add flocking of sheep to the list. Fernando Peruani from the Côte d’Azur University in Nice, France, led a study that examined the roles played by “leaders” and “followers” in driving the motion of flocks of sheep. His team combined observations of flocking with mathematical models to show that the sheep’s collective motion is governed both by the movement of a lead animal and the way in which other animals in the flock respond. Peruani and his gang also found that individual sheep alternate between leaders and followers in a seemingly random way. The team concludes that the collective motion of sheep is governed by both hierarchical and democratic processes within the flock. You herd it here first.

You can be sure that next year will throw up its fair share of quirky stories from the world of physics. See you next year!

As my wine glass gently weeps

See, swirl, sniff, sip and savour – these are the five S’s of wine tasting. You, or the oenophile (wine connoisseur) in your life may be well-versed in swirling that perfect glass of fruity Beaujolais, before deeply inhaling the bouquet, and then finally taking that first sip. While some people consider it a pretentious way to consume a beverage, these steps do have a direct impact on the taste of a glass of wine. Indeed, there’s a surprising amount of science that goes into each of the S’s of wine drinking.

Let’s start with the glass itself. While there’s nothing stopping you from drinking wine from any kind of vessel (including straight from the bottle, should it please you), the shape of a wine glass has a direct impact on the flavours we perceive. A traditional wine glass has four key components: the “foot” or the flat base of the glass; the “stem” or the spindly bit that you hold, which helps keep the wine at the right temperature; the “bowl” or the actual curved receptacle that holds the wine; and finally the “rim” or the edge of the glass.

The shape of the glass determines how the vapours of the ethanol – the alcoholic bit in wine – reaches the nose and mouth. The strength and intensity of a wine’s aroma depend on the size of the bowl relative to the rim – the bigger the bowl, the more aromas will be released; and the more tapered the rim, the easier it is for these scents to reach your nose. Most wine glasses are shaped so that the aromas are centred within the bowl, while the ethanol is pushed out to the rim, not reaching the nose.

Even the taste of the wine, once you sip it, is impacted by the shape of the glass. You’ll find yourself tilting your head either forwards (likely when tasting from a wide-brimmed glass) or backwards (while attempting to navigate your nose past the brim of a narrow flute). The tilt of your head determines the speed and intensity with which the wine enters your mouth, which in turn dictates how many of your tastebuds are impacted at the same time. This accounts for the strong “mouthfeel” of a full-bodied Merlot, for example.

Beyond the physical glass, aficionados are often tempted to swirl their wine, and comment on its “legs” as an indicator of quality. Also dubbed “tears”, “fingers” and even “church windows”, this is the ring of drops that forms near the top of your glass, and it is rooted in physics.

These tears are a consequence of wine being an inhomogeneous mix of water and alcohol (along with some sugars and acids). As you swirl your glass, most of the wine sloshes back down, but a thin film is left behind on the walls of the glass – capillary action making it climb the sides. What’s happening is that the alcohol and the water in the film begin to evaporate quicker than in the bulk of your drink – but the alcohol in the film evaporates faster than the water due to its higher vapour pressure. The alcohol’s swift evaporation and its consequent drop in concentration means that the surface tension of the film increases, pulling up liquid from the bottom of your glass, which has a lower surface tension (as it still has more alcohol).

This flow of liquid due to surface tension gradients is referred to as the “Marangoni effect” in honour of the Italian physicist Carlo Marangoni, who originally studied mass transfer along an interface between two phases due to a gradient in surface tension. But the first person to accurately describe the basic mechanism behind the “tears of wine” phenomenon, in 1855, was physicist James Thomson, the elder brother of Lord Kelvin.

While the Marangoni effect explains the flow of wine up the side of the glass, it was for many years unclear why the flow forms individual drops. But could gravity hold the answer? In 2019 Andrea Bertozzi and colleagues at the University of California, Los Angeles, carried out a theoretical analysis of the non-classical dynamics of wine glasses and wine tears, factoring in gravitational effects that were previously ignored (Phys. Rev. Fluids 5 034002).

Their model found that the film’s thickness plays a key role in how the tears are formed. Indeed, if the film is uniform and thick enough, it flows back down in a sheet. Their experiments and calculations instead showed that the liquid moves up in a bulging wave that leaves behind a thin film. They describe this as an unstable “reverse undercompressive shock wave”, which breaks up to form tears.

This type of Marangoni flow does not just affect wine but has an influence on everything from crystal growth in semiconductors to the radiation of heat in your laptop. In fact, over the last decade, the European Space Agency (ESA), NASA and the Japan Aerospace Exploration Agency have all carried out experiments to study the effect on the International Space Station, in microgravity, with a new ESA experiment due to start next year.

Despite all the physics involved, the tears of wine don’t indicate how good the wine is, but simply its alcohol content. Literally, more alcohol means more tears.

Materials and nanotechnology: our favourite research in 2022

Materials and nanotechnology are thriving fields for physicists, who often benefit from collaborating with chemists, biologists, engineers and, of course, materials scientists. This makes materials and nanotechnology fascinating to write about, and this year has been no exception. Here is a selection of some of our favourite materials and nanotechnology research stories that we published in 2022.

“Inherited nanobionics” makes its debut

The integration of nanomaterials with living organisms is a hot topic, which is why this research on “inherited nanobionics” is on our list. Ardemis Boghossian at EPFL in Switzerland and colleagues have shown that certain bacteria will take up single-walled carbon nanotubes (SWCNTs). What is more, when the bacteria cells split, the SWCNTs are distributed amongst the daughter cells. The team also found that bacteria containing SWCNTs produce a significantly more electricity when illuminated with light than do bacteria without nanotubes. As a result, the technique could be used to grow living solar cells, which as well as generating clean energy, also have a negative carbon footprint when it comes to manufacturing.

Advanced X-ray imaging reveals why golden medieval sculptures deteriorate

Much of the world’s cultural heritage exists in material form and scientists play important roles in preserving the past for future generations. In Switzerland and Germany researchers have used an advanced, non-invasive imaging technique to help restore medieval objects that are covered in zwischgold. This is a highly sophisticated material comprising an ultrathin gold layer that is backed by a thicker layer of silver. Zwischgold deteriorates over the centuries, but experts had been unsure of its original structure and how it changes with time, making restoration difficult. Now, a team led by Qing Wu at the University of Applied Sciences and Arts of Western Switzerland and Benjamin Watts at the Paul Scherrer Institute have used an advanced X-ray diffraction technique to show that zwischgold has a 30 nm-thick gold layer, compared to gold leaf, which is typically 140 nm. They also gained insights into how the material begins to separate from surfaces.

Perovskite solar cell survives the damp and heat

Film protects perovskite solar cells — A film that protects perovskite solar cells from adverse conditions such as high temperatures and moisture. (Courtesy: © 2022 KAUST)

The term “wonder material” is probably overused, but here at Physics World we think it is an apt description of the perovskites – semiconductor materials with properties that make them suitable for making solar cells. However, perovskite devices have their downsides, some of which are related to surface defects and ion migration. These problems are exacerbated by heat and humidity – the very conditions that practical solar cells must endure. Now, Stefaan De Wolf at the King Abdullah University of Science and Technology in Saudi Arabia and colleagues have created a perovskite device made from 2D and 3D layers that is more resistant to heat and humidity. This is because the 2D layers act as a barrier, stopping both water and ion migration from affecting 3D parts of the device.

Researchers find “lost” angular momentum

The conservation of angular momentum is a cornerstone of physics. This is why scientists had been puzzled over the fate of spin in some magnets, which appeared to vanish when the materials are bombarded by ultrashort laser pulses. Now, researchers at the University of Konstanz in Germany have found that this “lost” angular momentum is in fact transferred from electrons to vibrations of the material’s crystal lattice within a few hundred femtoseconds. Firing laser pulses at magnetic materials can be used to store and retrieve data, so understanding how angular momentum is transferred could lead to better storage systems. The Konstanz experiment could also lead to the development of new ways to manipulate spin – which could benefit the development of spintronic devices.

Long-lived hot electrons spotted in “wonder” semiconductor

The SUEM instrument in Santa Barbara — Hot electrons: the scanning ultrafast electron microscope at the University of California, Santa Barbara. (Courtesy: Matt Perko/UCSB)

Speaking of wonder materials, 2022 was the year of cubic boron arsenide. This semiconductor had been predicted to have two technologically significant properties – high hole mobility and high thermal conductivity. Both of these predictions were confirmed experimentally this year and the researchers who did that are honoured in our Top 10 Breakthroughs of 2022. But it has not stopped there, later this year Usama Choudhry and colleagues at the University of California, Santa Barbara, and the University of Houston used scanning ultrafast electron microscopy to confirm that “hot” electrons in cubic boron arsenide have long lifetimes. This is another highly desirable property that could prove useful in the development of solar cells and light detectors.

Solid-state cooling is achieved via electric field induced strain

It is estimated that 20% of all electricity used globally is expended on conventional vapour-compression refrigeration and air conditioning. Furthermore, the refrigerants used in these systems are powerful greenhouse gases that contribute significantly to global warming. As a result, scientists are trying to develop more environmentally friendly refrigeration systems. Now, Peng Wu and colleagues at Shanghai Tech University have created a solid-state caloric cooling system that uses electric fields, rather than the magnetic fields to create strain in a material. This is important because electric fields are much easier and much cheaper to implement than magnetic fields. What is more, the effect occurs at room temperature – which is an important requirement for a practical cooling system.

Magic-angle graphene switches from superconductor to ferromagnet

We are going to squeeze one more wonder material into this year’s round-up, and that is magic-angle graphene. This is created when layers of graphene are rotated relative to each other, creating a Moiré superlattice that has a range of properties that depend on the angle of the twist. Now, Jia Li and colleagues at Brown University in the US have used magic-angle graphene to create a material that exhibits both magnetism and superconductivity – properties that are usually at opposite ends of the spectrum in condensed-matter physics. The team interfaced magic-angle graphene with the 2D material tungsten diselenide. The complex interaction between the two materials allowed the researchers to transform graphene from a superconductor into a powerful ferromagnet. This achievement could give physicists a new way to study the interplay between these two usually separate phenomena.

Medical physics and biotechnology: our favourite research in 2022

From developing advanced machine-learning algorithms to building devices that will improve access to effective treatments for patients across the world, researchers working in medical physics, biotechnology and the many related fields continue to apply scientific techniques to improve healthcare worldwide. Physics World has reported on many such innovations in 2022, here are just a few of the research highlights that caught our eye.

AI in all areas

Artificial intelligence (AI) plays an increasingly prevalent role in the medical physics arena – from dealing with the vast amount of data generated during diagnostic imaging, to understanding the evolution of cancer in the body, to helping design and optimize treatments. With this in mind, Physics World hosted an AI in Medical Physics Week in June, looking at the use of deep learning for applications including online adaptive radiation therapy, PET imaging, proton dose calculation, analysis of head CT scans and identifying COVID-19 infection in lung scans.

Earlier in the year, a dedicated session at the APS March Meeting examined some of the latest medical applications of AI and machine learning, including deep learning for diagnosing and monitoring brain disorders and neurodegenerative disease, and employing AI for image registration and segmentation. Another intriguing study was EPFL’s use of a neural network to create an intelligent microscope that detects subtle precursors to rare biological events and controls its acquisition parameters in response.

The promise of proton FLASH

In a development that also made it into our top 10 Breakthroughs of the Year for 2022, this year’s ASTRO Annual Meeting saw Emily Daugherty from the University of Cincinnati Cancer Center report the findings from the first clinical trial of FLASH radiotherapy. FLASH treatments – in which therapeutic radiation is delivered at ultrahigh dose rates – hold promise for reducing normal tissue toxicity while maintaining anti-tumour activity. In this study, the researchers used FLASH proton therapy to treat 10 patients with painful bone metastases. They demonstrated the feasibility of the clinical workflow and showed that the treatment was as effective as conventional radiotherapy for pain relief, without causing unexpected side effects.

The study also represents the first-in-human use of proton FLASH. Most of the previous preclinical FLASH studies employed electrons; but electron beams only travel a few centimetres into tissue while protons penetrate far deeper. Hoping to exploit this advantage, many other groups are also investigating proton FLASH, including scientists at the University of Pennsylvania who used computational modelling to find out which is the most effective delivery technique for FLASH proton beams, and researchers from Erasmus University Medical Center, Instituto Superior Técnico and HollandPTC, who developed an algorithm that optimizes proton pencil-beam delivery patterns to maximize FLASH coverage.

Bringing back sight

Restoring vision to those who have lost the ability to see is a substantial research task. This year we reported on two studies that aim to bring this goal a step closer. Researchers at the University of Southern California are exploring the use of ultrasound stimulation to treat blindness caused by retinal degeneration. While visual prostheses that restore sight via electrical stimulation of retinal neurons have already been successfully used in patients, these are invasive devices that require complex implantation surgeries. Instead, the team demonstrated that stimulating a blind rat’s eyes with non-invasive ultrasound can activate small groups of neurons in the animal’s eye.

Cornea implant study — Success story: The cornea implant restored sight to completely blind patients. (Courtesy: Thor Balkhed/Linköping University)

Elsewhere, a team in Sweden, Iran and India developed a new way to produce artificial corneas, using medical-grade collagen sourced from pig skin (a purified byproduct of the food industry) that the researchers chemically and photochemically treated to improve its strength and stability. In a pilot study of 20 patients, they showed that their implants were strong and resistant to degrading and could fully restore patients’ sight through minimally invasive surgery. Based on this success, Mehrdad Rafat and his team hope that the new approach could address the shortage of donor corneas for transplant and increase the treatment options for the many people worldwide in urgent need of new corneas.

Brain–computer interface innovations

Brain–computer interfaces (BCIs) provide a bridge between the human brain and external software or hardware. This year saw researchers successfully use an implanted BCI to enable a person with complete paralysis to communicate. The team – from the Wyss Center for Bio and Neuroengineering, ALS Voice and the University of Tübingen – implanted two tiny microelectrode arrays into the surface of the participant’s motor cortex. The electrodes record neural signals, which are decoded and used in an auditory feedback speller that prompts the user to select letters. The patient, who had amyotrophic lateral sclerosis (ALS) and was in a completely locked-in state with no remaining voluntary movement, learned how to alter his own brain activity according to the audio feedback received, enabling him to form words and sentences and communicate at an average rate of about one character per minute.

BCI communication — Generating language: Neural data recorded by an implanted brain–computer interface are decoded and analysed in real time to control spelling software. (Courtesy: The Wyss Center, Geneva)

As an alternative to using implanted electrodes to sense brain activity, neural signals can also be collected non-invasively using electroencephalography (EEG) electrodes attached to the scalp. A team at the University of Technology Sydney developed a novel graphene-based biosensor that detects EEG signals with high sensitivity and reliability – even in highly saline environments. The sensor, which is made from epitaxial graphene grown on a silicon carbide-on-silicon substrate, combines the high biocompatibility and conductivity of graphene with the physical robustness and chemical inertness of silicon technology.

Quantum science and technology: our favourite research in 2022

Quantum physicists celebrated in October when the Nobel committee awarded a long-awaited physics prize to Alain Aspect, John Clauser and Anton Zeilinger for their pioneering research on quantum entanglement. But the community certainly hasn’t been resting on its laurels, and with so many other exciting developments in 2022, it’s hard to pick just a few highlights. Nevertheless, here are some results that stood out for us in the fields of quantum sensing, quantum information, quantum computing, quantum cryptography and fundamental quantum science.

Sensing accelerations below the quantum limit

In quantum mechanics, the principle of delocalization states that a quantum particle can, in some hand-wavy sense, be in multiple places at once. The principle of entanglement, meanwhile, states that quantum particles experience a connection that allows the condition of one particle to determine that of another, even across vast distances. In November, physicists at JILA in Colorado, US, used a combination of entanglement and delocalization to suppress noise that had previously made it impossible to sense accelerations below the so-called quantum limit. This limit is set by the quantum noise of individual particles, and it has long been a significant constraint on the precision of quantum sensors. Overcoming it is thus a major step forward.

Teleporting entanglement from Alice to Charlie via Bob

Sending quantum information from one node in a network to another isn’t easy. If you encode the information in photons sent down an optical fibre, losses in the fibre eat away at the signal’s fidelity until it becomes unreadable. If you instead use quantum entanglement to teleport the information directly, you introduce other processes that, alas, also degrade the signal. Adding a third node to the network, as physicists at QuTech in the Netherlands did in 2021, only makes the task more difficult. That’s why it’s so impressive that the QuTech researchers followed up their earlier success by teleporting quantum information from a sender (Alice) to a receiver (Charlie) via an intermediate node (Bob). Although the fidelity of the Alice-Bob-Charlie transmission was only 71%, that is higher than the classical limit of 2/3, and achieving it required the researchers to combine and optimize several challenging experiments. Will Dave, Edna and Fred nodes join the network in 2023? We’ll see!

Noise-resistant quantum computing

Photo of the ion trap used in the experiment, viewed through a port in a vacuum chamber and bathed in pink light — Physical and logical qubits: The ion trap used in the experiment, seen through the window of an ultrahigh vacuum chamber. (Courtesy: Robbie Shone)

In case it wasn’t clear from the first two highlights in this list, noise is a huge problem in quantum science. This is as true for computing as it is for sensing and communication, which is why correcting these noise-induced errors is so important. Physicists made several advances on this front in 2022, but one of the most significant came in May when researchers at the University of Innsbruck, Austria and RWTH Aachen University in Germany demonstrated a full set of fault-tolerant quantum operations for the first time. Their ion-trap quantum computer uses seven physical qubits to make each logical qubit, plus “flag” qubits to signal the presence of dangerous errors in the system. Crucially, the error-corrected version of the system performed better than the simpler uncorrected one, illustrating the possibilities of the technique.

Device-independent quantum key distribution

Information security is quantum cryptography’s USP, but information is only ever as secure as the weakest link in the chain. In quantum key distribution (QKD), one potential weak link is the devices used to send and receive the keys, which are vulnerable to conventional hacks (like someone breaking into a node and tampering with the system) even though the keys themselves are secure against quantum ones. One alternative is to use device-independent QKD (DIQKD), which uses measurements of Bell inequalities in photon pairs to confirm that the key-generation process hasn’t been fudged. In July, three independent groups of researchers demonstrated DIQKD experimentally for the first time – in one case by generating 1.5 million entangled Bell pairs over a period of eight hours and using them to generate a shared key 95 884 bits long. Although the key generation rate needs to be higher to make DIQKD practical for real-world encrypted networks, the proof of principle is stunning.

Entangling an electron and a photon

Illustration of the coupled ring microresonator — Entangled pairs: in this artistic representation of the experiment, a beam of free electrons (yellow) passes next to a ring-shaped microresonator (black). The evanescent interaction between an electron and the microresonator creates a photon (turquoise) that is entangled with the electron. (Courtesy: Ryan Allen/Second Bay Studios)

The other entangled particles in this highlights list are all identical: photons entangled with other photons, ions with other ions, atoms with other atoms. But there’s nothing in quantum theory that demands this kind of symmetry, and an emerging new class of “hybrid” quantum technologies actually relies on mixing things up. Enter researchers led by Armin Feist of the Max Planck Institute for Multidisciplinary Sciences in Germany, who showed in August that they could entangle an electron and a photon using a ring-shaped optical microresonator and a beam of high-energy electrons that passes the ring at a tangent. The technique has applications for a quantum process called “heralding” in which detecting one particle in an entangled pair indicates that the other particle is available for use in a quantum circuit – a great example of how today’s fundamental advances drive tomorrow’s innovations.

A grab bag of quantum weirdness

Finally, as is traditional (we’ve done it twice, therefore it’s a tradition), no list of quantum highlights is complete without a nod to all that is strange and mind-boggling in the field. So let’s hear it for the US researchers who used a quantum processor to simulate the teleportation of information through a wormhole in space–time; a group in Italy and France who put hard numbers on the indistinguishability of indistinguishable photons; an international team who used quantum violations of classical causality to better understand the nature of cause-and-effect; and an intrepid pair of physicists at the University of Edinburgh, UK, who showed that quantum signals would be a good way for technologically advanced aliens to establish contact across interstellar distances. Thanks for keeping quantum weird!

This article was amended on 04/01/2023 to include a reference to a third group of device-independent QKD researchers who contributed to this year’s advances.

The ethical dilemmas of renaming scientific principles that honour fallen idols

Tár is a fictional film about a classical-music conductor who soars and crashes. Released in 2022, it features Lydia Tár (Cate Blanchett) who uses her power at the Berlin Philharmonic authoritatively but manipulatively. She cows some students, flirts with others and misuses colleagues. Then a doctored video of Tár goes viral, her name becomes anathema and she’s fired. The movie ends with her in a dead-end job at a kids’ theme park in an unnamed, poor part of the world.

Scientists, too, have soared and fallen. In 2022 Leiden University astronomer Tim de Zeeuw was removed from posts for his “extremely unacceptable” behaviour, while the US National Academy of Sciences expelled Peruvian archaeologist Luis Jaime Castillo Butters for sexual harassment. In 2007 the Nobel-prize-winning molecular biologist James Watson was forced to retire as chancellor of Cold Spring Harbor Laboratory (CSHL) for making statements on race deemed “incompatible with CSHL’s mission and values”.

But is it right to erase someone’s professional positions, memberships or titles on the basis of their opinions or conduct? At first sight, it seems the correct thing to do. Surely to make science a better place we must root out and punish bad behaviour. Surely we must crack down on people in positions of power for their misdemeanours. Many will applaud the decision, for example, to remove Watson’s honorary titles and strip his name from CSHL’s school of biological sciences.

Unfortunately, renaming in science is not as straightforward as one might think.

Let me consider just cases involving “eponymy”, or naming something after a scientist. Four hundred years ago, in his allegory New Atlantis, the philosopher Francis Bacon recognized that creating tributes was important to inspire other scientists and to give those trailblazers respect in the society that surrounds, supports and depends on them. That’s why Bacon equipped his ideal world with galleries of “statues of all principal inventors” in brass, marble, silver and gold.

But whereas Bacon’s utopian science-dependent world was static and stable, we know that acceptable moral behaviours in our world evolve. Slavery and racism, for example, were once deemed normal but are now abhorrent. We want to reinforce some norms we inherit, and repudiate others. We do the first in part, as in Bacon’s world, by constructing tributes, and the second sometimes by re-evaluating and renaming these tributes.

It’s why the Royal Astronomical Society, for example, has insisted that authors writing in its journals use the initials “JWST” instead of “James Webb Space Telescope” because of the alleged role that Webb (a former NASA administrator who died in 1992) had in purging gay people from the US Federal workforce while Webb was undersecretary of state in 1949–1952. (NASA has not changed the mission’s name, citing insufficient evidence.)

It’s why the physicist Michael Pepper has called for the Stark effect – the splitting of spectral lines in an electric field – to be renamed because of the pro-Nazi and antisemitic actions of the Nobel laureate Johannes Stark, who died almost 70 years ago. And it’s why the Entomological Society of America removed the name of Carl Linnaeus – who died in 1778 – from the title of its annual quiz competition for being a proponent of racist ideas.

Why, who and what?

One problem is: who should decide these things? In some areas of science, it’s easy. The names and symbols of new chemical elements, for example, are bestowed by the International Union of Pure and Applied Chemistry, while asteroid names are approved by the International Astronomical Union. But physics is trickier. Many names arise locally without official conferral – Ampère’s law was named by James Clerk Maxwell – and are questioned only by information that happens, usually accidentally, to come to light.

As parts of our language, names belong to social life differently, and their existence has tremendous inertia

A second problem involves the criteria to decide whose names get culled. This, too, is ambiguous. In Serving the Reich: the Struggle for the Soul of Physics under Hitler, the science writer Philip Ball illustrates the “grey zone between complicity and resistance” by looking at the lives of Max Planck, Peter Debye and Werner Heisenberg. They each contributed to a greater or less extent to Nazi Germany, but who was villainous, who virtuous? Heisenberg worked on the German atomic-bomb effort, but I’ve not heard anyone calling for his uncertainty principle to be renamed.

Finally, renaming things in physics is not simple from a practical point of view. Monuments are raised following an explicit decision to glorify someone and to design, fund and construct the monument; if the honour is rethought, these monuments can be physically destroyed, put in a museum or basement, or left standing with contextualization. But as parts of our language, names belong to social life differently, and their existence has tremendous inertia.

Textbooks would have to be rewritten, exams changed and papers updated to avoid confusion. Meanwhile, I suspect that renaming only occurs when the pickings are painless. Earlier this year, the Schrödinger Lecture Theatre at Trinity College Dublin was renamed and restored to its previous title of Physics Lecture Theatre after reports of Schrödinger’s sexual abuse of girls. But how should we go about renaming the Schrödinger equation? It’s far more famous, but where are the calls to rebrand it?

The critical point

At the end of Tár, a viewer may wonder whether, in the long run, a musical community is better served when an orchestra replaces its brilliant but flawed conductor with a mediocre, uncontroversial one. Scientists, too, may similarly wonder whether the community is better served by replacing the names of individuals whose past behaviour is judged unacceptable in the present.

Is removing a name good because it avoids appearing to endorse the inappropriate behaviour of a scientist and encourages others to do a better job themselves? Or is removing a name bad because it makes us complacent by suggesting that we’ve eliminated a problem and don’t need to worry about it anymore, and in allowing us to pretend to ourselves that physics is done only by the morally stainless?

What, in other words, is the ethics of eponymy? Readers with insights should inform me and I’ll write about the topic in a future column.

JWST is performing ‘phenomenally’ one year on, say scientists

It’s been a year since the James Webb Space Telescope (JWST) launched, and after its dangerous deployment and careful collimation, it’s finally sending back incredible images and data. Getting from the launchpad to full operations, however, was no easy task. Here’s a reminder of how it all happened.

Christmas Day 2021: after nearly 25 years of development, the JWST soared into space atop an Ariane 5 rocket. Its launch was a triumph over technological tribulations, budget and schedule overruns, and even a (temporary) cancellation by the US Congress. Consequently, emotions were high as the launchpad countdown neared zero.

“It was tense,” admits Susan Mullally, the JWST’s deputy project scientist at the Space Telescope Science Institute (STScI) in Baltimore. “I couldn’t believe it was real,” adds Naomi Rowe-Gurney, a JWST GTO (Guaranteed Time Observations) postdoc at NASA’s Goddard Space Flight Center where she is supporting the Planetary Systems Team. “I was expecting another delay of some kind. I thought it was never going to launch.”

A hazardous journey

The stop–start nature of the project’s development came about in part because of the increasing complexity of the telescope, which features a segmented 6.5-metre primary mirror as well as a fragile, five-layer, tennis-court-sized insulating sunshield. Both elements had to unfold like origami after being scrunched up to fit inside the rocket faring – a 30-day process that coincided with the telescope’s journey to the L2 Lagrange point on the opposite side of the Earth to the Sun, 1.6 million kilometres from Earth.

This point is much too far away for the kind of astronaut-assisted servicing the Hubble Space Telescope received for its faulty optics in 1993. If something had gone wrong with the JWST’s mirror during its deployment, astronomers would have been left with a $10 billion white elephant floating in deep space.

“Those first 30 days were pretty nerve-wracking, because any problem was a single-point failure and would mean we wouldn’t have a telescope,” Rowe-Gurney says.

All told, there were 344 such possible points of failure: 344 points where the telescope’s intricate moving parts had to work perfectly in the cold vacuum of space. Yet work they did – “phenomenally so” according to NASA Goddard’s Jane Rigby, who spoke at the First Science Results from JWST conference held at STScI earlier this month.

“The day when I knew this was actually going to work was when that main boom swung out, and the secondary mirror folded out, and we actually had a telescope,” Rowe-Gurney says. “Even if the subsequent deployments didn’t work, we could capture light and put it into the instruments.”

Focusing the telescope

With both mirrors deployed, the next step was to focus the 18 hexagonal beryllium segments of the primary mirror. This was accomplished in seven phases. Initially, each segment produced a different unfocused image, so the first phase was to recognize which image belonged to which mirror segment. The next step was to roughly align the mirrors so that the 18 images were all in focus. After that, the segments were further adjusted so that they began to focus at the same point.

This was followed by various degrees of fine-tuning and making sure that the focus fell within the fields of view of the different instruments, and then by a series of corrections to ensure the segments were aligned to within 50 nm of each other. Finally, after a three-month process, the telescope was in focus.

Breaking the speed limit

With the telescope in good shape, the next step was to calibrate its individual instruments: the Near-Infrared Camera (NIRCam), the Near-Infrared Spectrometer (NIRSpec), and MIRI, the suite of detectors that make up the Mid-Infrared Instrument.

A JWST image of the DART impact, which appears as a burst of dusty reddish material with a bright flash at the centre — Caught on camera: the JWST was able to image the aftermath of the DART impact by tracking it at three times its nominal safe tracking speed. (Courtesy: NASA/ESA/CSA/STScI)

Distant, deep-space objects appear fixed on the sky, but objects in the solar system move against that background of stars, nebulae and galaxies. Therefore, to image planets, moons, comets and asteroids, the JWST has to track them by physically turning the spacecraft. Prior to launch, a tracking speed limit was introduced: 30 milliarcseconds per second, where one arcsecond is 1/3600th of a degree).

Once in space, however, the team realized this limit was a little pessimistic. “We were testing how fast we could track, and we realized that we could actually do much faster,” says Rowe-Gurney, who was involved in commissioning instruments for collecting data on moving targets and scattered light.

The increased tracking speed came in useful a few months later, when the JWST observed the aftermath of the DART (Double Asteroid Redirection Test) impact on the small asteroid Dimorphos. The DART mission was Physics World’s scientific breakthrough of the year for 2022, and the JWST was able to image debris ejected from its impact by tracking three times faster than the initial limit, keeping the asteroid in the field of view without blurring. Indeed, the telescope has since achieved tracking speeds of up to 120 milliarcseconds per second. However, the faster it tracks, the lower its tracking efficiency, leading to a middle-ground compromise. “In the next year the safe tracking rate will be put up to 75 milliarcseconds per second, more than doubling the speed limit, so we’ll be able to follow even more objects in the solar system without breaking the telescope,” Rowe-Gurney says.

Removing scattered light

When the JWST stares at a bright object – a planet, a star, even a distant quasar – some of the excess light forms a diffraction pattern. This pattern is the cause of the “spikes” seen around foreground stars in many of the JWST’s images, and although pretty, it can obscure scientific details. Fortunately, every telescope’s unique diffraction pattern can be described as a point spread function, and by characterizing the shape of this point spread function for the JWST and its instruments, astronomers can remove the extraneous light from images when necessary.

JWST image of a pair of merging galaxies. The galaxies appear as a dense clump of red stars surrounded by diffuse blue gas and dust. There are diffraction "spikes" emerging from the image in a star pattern — Extra light: a JWST image of IC 1623, which is a system of two merging galaxies. The galactic core is bright enough to create diffraction spikes in the image. (Courtesy: ESA/Webb/NASA/CSA/L Armus and A Evans)

A case in point was the JWST’s image of the Wolf–Rayet star WR 140, which is located 5000 light-years away. When first imaged by the JWST, astronomers were stunned to see 17 concentric rings, or shells, around the star. These rings were initially thought to be imaging artefacts from the telescope, but after removing the point spread function, the rings were still there. Further investigation based on simulations showed that stellar winds from binary stars can produce rings of dust where they clash and condense. What is more, the pattern of the simulated rings precisely matched the pattern of rings around WR 140, even down to a linear feature cutting through the rings due to enhanced infrared emission in our line of sight.

The observations of WR 140 represent the first time a colliding wind structure around a binary star has been mapped in 3D. But if astronomers had not first modelled the pattern of scattered light leaking into the telescope so they could remove it, it would have been impossible to discern what the observations were telling us.

Astronomers’ new toy

The Wolf–Rayet star example shows how vital it is to get to know the telescope while making observations. “It’s something you have to think about a lot,” Mullally says. “Every step of the way you’re hoping to have an expert on your team who knows as much as possible either about the instrument or about how those types of observations are taken.”

Image of the star WR 140, which appears as a burst of purplish light at the centre, surrounded by thin rings like water ripples in a pond — Ring around the rosie: concentric rings of dust around the star WR 140. (Courtesy: NASA/ESA/CSA/STScI/JPL–Caltech)

Accordingly, one of the motivations behind the JWST’s Early Release Science (ERS) was to help a few astronomers become familiar with the telescope and its instruments so they can bring others up to speed for later observing cycles. “It’s like a new toy,” says Rowe-Gurney. “There’s a lot of work going into how to process and calibrate the data to make sure it’s reliable.”

Fortunately, the JWST is playing ball. “Instrument scientists might say they are still getting to know their instruments and how to go about removing little systematics and artefacts and things like that in your data,” says Mullally, “but overall the impression I’m getting from everybody is that the telescope is performing wonderfully.”

Impact risk

So far, there is only one caveat to the JWST’s performance: the damage caused by micrometeoroid impacts. On average, the telescope’s mirror is struck once a month by something large enough to affect wavefront sensing, which is the telescope’s ability to detect errors in the alignment its optics that can manifest as light waves going out of phase. This reduction in wavefront sensing can make images less sharp.

Such impacts were anticipated before launch, and were not expected to be big enough to threaten the telescope’s lifespan. However, in May 2022 one of the mirror segments received a larger-than-typical impact. In her talk at the First Science Results from JWST conference, Rigby reported that this impact left a wound a foot across, increasing the telescope’s total wavefront error by 9 nm. This is significant because if the wavefront error reaches 150 nm, the telescope will no longer be sensitive enough to meet its scientific targets – meaning that just 10 impacts of a similar scale would be “game over” for the JWST.

Somewhat alarmed by this prospect, NASA has convened a micrometeoroid working group to investigate the risk. The micrometeoroid population at L2 is well known; what isn’t clear is the relationship between the kinetic energy of impacts and the degradation of wavefront sensing. Are such large impacts extremely rare and the JWST was simply unlucky in May? Or will the telescope experience more serious impacts at a greater frequency than predicted?

Image of a high-redshift quasar taken by the JWST

Quasars, exoplanets and the atmospheres of distant worlds: more on the first results from the JWST

Until the working group comes up with answers, the telescope’s managers are mitigating the risk by encouraging astronomers to time their observations (where possible – time-sensitive observations are exempt) so that the telescope is not pointing into the “rain” of micrometeoroids.

If this system succeeds, or the working group comes up with a reassuring answer about impact odds, the JWST should have a long life ahead of it. Thanks to its flawless launch and a journey to L2 that required minimal course corrections, the scope has enough propellant on board to continue its mission for at least another 27 years. If the mission’s first 12 months are any indication, these 27 years should produce reams of sensational new views and data from a superb instrument, with a high likelihood of transforming astrophysics, exoplanet studies, cosmology and more. The rollercoaster ride of the JWST’s launch may be over, but the real journey is just beginning.

Science must do more to include people with disabilities, says study

Disabilities are created not only by an individual’s circumstances, but also by systems and social processes designed without them in mind. That is according to a new study that calls for more proactive inclusion efforts within science, technology, engineering, mathematics and medicine (Nature Communications 13 7208).

The study was carried out by a team led by Siobhán Mattison of the University of New Mexico, who says that the COVID-19 response proved that substantial changes can be implemented quickly if prioritized. What’s more, the adoption of remote working made work more accessible for some individuals. Building on these insights, Mattison’s team has drawn up an approach to inclusion comprising three strands: flexibility, accommodations and modifications.

“Flexibility” means recognizing that individuals’ needs vary widely, and therefore allowing people to work in a broad range of ways, for example by having a hybrid workforce.

“Accommodations” refers to adjustments to improve accessibility, like designing spaces with ramps, while “modifications” says that job duties should sometimes be altered where flexibility and accommodations are not enough, such as making summer teaching count towards teaching requirements.

“One of the most important things that institutions can do up front is to set aside funding to support recruitment and retention of scholars with disabilities,” Mattison told Physics World. “Conducting listening sessions is essential to evaluate needs and priorities so that money is spent in ways that are informed by people with first-hand experience of disability.”

Such activities are likely to have significant long-term benefits. After all, many people will experience disability at some point during their life – as the emergence of long COVID has brought into focus.

Co-author Logan Gin from Brown University highlights the advantages of having diverse perspectives in the workforce. “Researchers get to select the questions that are asked and answered, defining what is important for their disciplines,” he explains.

Colour of flower oscillates with time to improve pollination

An extremely rare case of a flower that oscillates in colour over time has been discovered by researchers in Japan. The team, led by Nobumitsu Kawakubo at Gifu University, showed that the transformations are tied to cyclic changes in the flowers’ reproductive organs, which act to guide pollinating insects towards them.

Over 450 plant species are known to change the colours of their flowers. Botanists generally believe that these changes are related to the pollination conditions in each flower, signalling to insects where the best nectar can be found.

The vast majority of these colour changes are unidirectional, meaning once colour has changed, it can never change back. Yet in their study, Kawakubo’s team discovered an example of a far rarer bidirectional flower, which oscillates back and forth between two colours. Named Causonis japonica, this vine plant is native to tropical regions of Asia and Australia and is often considered to be a weed.

Fading to pink

At the start of its oscillation cycle, the researchers found that C. japonica’s flower disk is orange in colour, but soon fades to pink. After several hours of daylight, the flowers recover their orange hue, and the cycle repeats.

Through their analysis, the researchers discovered that these changes are strongly tied to levels of carotenoid pigments present in the flowers. Carotenoids are best known for giving carrots their distinctive orange hue, but are also responsible for producing red, orange, and yellow colours in organisms as diverse as pumpkins, lobsters, and bacteria surrounding volcanic hot springs.

In C. japonica, the researchers found that levels of carotenoids peaked at times when its flowers featured pollen-producing male reproductive organs. This roughly coincided with an uptick in nectar secretion in the flower, providing optimal conditions for insect pollination.

As the male organs withered and detached from the flower, its accumulated carotenoid molecules degraded, and the flower turned pink. Yet after a few hours of daylight, the flowers then developed pollen-fertilizing female reproductive organs. As carotenoids accumulated once again, the flowers turned from pink to orange, and began to secrete more nectar. Eventually, these organs wither away, the flowers turn pink, and the cycle begins again.

Having uncovered this oscillating phase changes, Kawakubo and colleagues will now aim to learn more about the biological mechanisms involved. Where C. japonica was once widely seen as a nuisance in Japan, the team hopes that their discoveries of its remarkable behaviour could spark a new appreciation of the plant. A better understanding of how colour changes take place in other flowers may also lead to better techniques for protecting threatened plant species.

The research is described in Scientific Reports.

Large tunnel magnetoresistance appears at room temperature in a miniaturized magnetic tunnel junction

Magnetic tunnel junctions (MTJs), which consist of two ferromagnets separated by a non-magnetic barrier material, are found in a host of technologies, including magnetic random-access memories in computer hard disk drives as well as magnetic sensors, logic devices and electrodes in spintronic devices. They do have a major drawback, though, which is that they do not operate well when miniaturized to below 20 nm. Researchers in China have now pushed this limit by developing a van der Waals MTJ based on a semiconducting tungsten diselenide (WSe₂) spacer layer less than 10 nm thick, sandwiched between two ferromagnetic iron gallium telluride (Fe₃GaTe₂) electrodes. The new device also has a large tunnel magnetoresistance (TMR) at 300 K, making it suitable for memory applications.

“Such a large TMR in ultrathin MTJs at room temperature has never been reported before in all-two-dimensional van der Waals (vdW) MTJs,” says Kaiyou Wang, who directs the State Key Laboratory for Superlattices and Microstructures in the Institute of Semiconductors, Chinese Academy of Sciences, Beijing and is also affiliated with the Center of Materials Science and Optoelectronics Engineering at the University of Chinese Academy of Sciences. “Our work opens a realistic and promising route for next-generation non-volatile spintronic memories beyond the current state of the art.”

Room temperature ferromagnetism

Wang, who led the new device’s development together with Haixin Chang of the State Key Laboratory of Material Processing and Die & Mold Technology at Huazhong University of Science and Technology and the Wuhan National High Magnetic Field Center, attributes its large TMR to two features. The first is the intrinsic properties of Fe₃GaTe₂, which is ferromagnetic above room temperatures. “We have investigated the magnetoresistance of a number of van der Waals ferromagnet/semiconductor junctions for quite a few years in which the Curie temperature (the temperature above which a permanent magnet loses its magnetism) of the ferromagnet is far below room temperature,” he notes. “We found large magnetoresistance and efficient spin injection can only be achieved in nonlinear transport behaviour of ferromagnet/semiconductor junctions.”

In contrast to the materials Wang and colleagues investigated previously, Fe₃GaTe₂ (which the team discovered relatively recently) has a Curie temperature of more than 380 K. Its magnetic anisotropy is also comparable to (or even better than) that of CoFeB, a ferrimagnet widely employed in spintronics. (Unlike ferromagnets, where neighbouring magnetic moments are parallel to each other, in ferrimagnets the moments are anti-parallel but unequal in magnitude, yielding a residual spontaneous magnetism.) Importantly, Fe₃GaTe₂ and CoFeB both have highly polarized Fermi surfaces (the boundary between occupied and unoccupied electron energy states that defines many of properties of metals and semiconductors), which for CoFeB has meant that large spin-polarized electron sources operating at room temperature can be made from it.

A better spacer and device design

The second factor in the new device’s success, Wang says, is the high quality of the WSe₂ barrier. “We discovered that using Fe₃GaTe₂ on its own is not enough and that we could only achieve a small room-temperature magnetoresistance (of around 0.3%) in one type of all-vdW spin-valves using a MoS₂ spacer,” he explains. “We realized we needed a much better spacer and device design that allowed for highly efficient electron tunnelling.”

Wang says the team’s work confirms that very large TMRs can be achieved at room temperature in all-vdW heterostructures, which he describes as a crucial step towards 2D spintronics applications. “Beyond that, the highly efficient spin injection into semiconductors could allow us to investigate semiconductor spin physics and develop new concept semiconductor spintronic devices,” he says.

Spurred on by their results, the researchers are now busy adjusting the thickness of the spacer layer in an attempt to further increase the TMR. One promising avenue they are exploring is to use the wide-bandgap semiconductor gallium arsenide (GaSe) or the insulator hexagonal boron nitride (hBN) as a spacer material.

They detail their present study in Chinese Physics Letters.