Audio Editor Olympics 2024: Who Wins The Gold? This week Audacity, the free digital audio workstation, released some major upgrades that are quite frankly, awesome. Over time they have been adding features like Real Time effects which means you can play your audio while adjusting the…
Scientists find a human “fingerprint” in the upper troposphere’s increasing ozone
Ozone can be an agent of good or harm, depending on where you find it in the atmosphere. Way up in the stratosphere, the colorless gas shields the Earth from the sun’s harsh ultraviolet rays. But closer to the ground, ozone is a harmful air pollutant that can trigger chronic health problems including chest pain, difficulty breathing, and impaired lung function.
And somewhere in between, in the upper troposphere — the layer of the atmosphere just below the stratosphere, where most aircraft cruise — ozone contributes to warming the planet as a potent greenhouse gas.
There are signs that ozone is continuing to rise in the upper troposphere despite efforts to reduce its sources at the surface in many nations. Now, MIT scientists confirm that much of ozone’s increase in the upper troposphere is likely due to humans.
In a paper appearing today in the journal Environmental Science and Technology, the team reports that they detected a clear signal of human influence on upper tropospheric ozone trends in a 17-year satellite record starting in 2005.
“We confirm that there’s a clear and increasing trend in upper tropospheric ozone in the northern midlatitudes due to human beings rather than climate noise,” says study lead author Xinyuan Yu, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).
“Now we can do more detective work and try to understand what specific human activities are leading to this ozone trend,” adds co-author Arlene Fiore, the Peter H. Stone and Paola Malanotte Stone Professor in Earth, Atmospheric and Planetary Sciences.
The study’s MIT authors include Sebastian Eastham and Qindan Zhu, along with Benjamin Santer at the University of California at Los Angeles, Gustavo Correa of Columbia University, Jean-François Lamarque at the National Center for Atmospheric Research, and Jerald Zimeke at NASA Goddard Space Flight Center.
Ozone’s tangled web
Understanding ozone’s causes and influences is a challenging exercise. Ozone is not emitted directly, but instead is a product of “precursors” — starting ingredients, such as nitrogen oxides and volatile organic compounds (VOCs), that react in the presence of sunlight to form ozone. These precursors are generated from vehicle exhaust, power plants, chemical solvents, industrial processes, aircraft emissions, and other human-induced activities.
Whether and how long ozone lingers in the atmosphere depends on a tangle of variables, including the type and extent of human activities in a given area, as well as natural climate variability. For instance, a strong El Niño year could nudge the atmosphere’s circulation in a way that affects ozone’s concentrations, regardless of how much ozone humans are contributing to the atmosphere that year.
Disentangling the human- versus climate-driven causes of ozone trend, particularly in the upper troposphere, is especially tricky. Complicating matters is the fact that in the lower troposphere — the lowest layer of the atmosphere, closest to ground level — ozone has stopped rising, and has even fallen in some regions at northern midlatitudes in the last few decades. This decrease in lower tropospheric ozone is mainly a result of efforts in North America and Europe to reduce industrial sources of air pollution.
“Near the surface, ozone has been observed to decrease in some regions, and its variations are more closely linked to human emissions,” Yu notes. “In the upper troposphere, the ozone trends are less well-monitored but seem to decouple with those near the surface, and ozone is more easily influenced by climate variability. So, we don’t know whether and how much of that increase in observed ozone in the upper troposphere is attributed to humans.”
A human signal amid climate noise
Yu and Fiore wondered whether a human “fingerprint” in ozone levels, caused directly by human activities, could be strong enough to be detectable in satellite observations in the upper troposphere. To see such a signal, the researchers would first have to know what to look for.
For this, they looked to simulations of the Earth’s climate and atmospheric chemistry. Following approaches developed in climate science, they reasoned that if they could simulate a number of possible climate variations in recent decades, all with identical human-derived sources of ozone precursor emissions, but each starting with a slightly different climate condition, then any differences among these scenarios should be due to climate noise. By inference, any common signal that emerged when averaging over the simulated scenarios should be due to human-driven causes. Such a signal, then, would be a “fingerprint” revealing human-caused ozone, which the team could look for in actual satellite observations.
With this strategy in mind, the team ran simulations using a state-of-the-art chemistry climate model. They ran multiple climate scenarios, each starting from the year 1950 and running through 2014.
From their simulations, the team saw a clear and common signal across scenarios, which they identified as a human fingerprint. They then looked to tropospheric ozone products derived from multiple instruments aboard NASA’s Aura satellite.
“Quite honestly, I thought the satellite data were just going to be too noisy,” Fiore admits. “I didn’t expect that the pattern would be robust enough.”
But the satellite observations they used gave them a good enough shot. The team looked through the upper tropospheric ozone data derived from the satellite products, from the years 2005 to 2021, and found that, indeed, they could see the signal of human-caused ozone that their simulations predicted. The signal is especially pronounced over Asia, where industrial activity has risen significantly in recent decades and where abundant sunlight and frequent weather events loft pollution, including ozone and its precursors, to the upper troposphere.
Yu and Fiore are now looking to identify the specific human activities that are leading to ozone’s increase in the upper troposphere.
“Where is this increasing trend coming from? Is it the near-surface emissions from combusting fossil fuels in vehicle engines and power plants? Is it the aircraft that are flying in the upper troposphere? Is it the influence of wildland fires? Or some combination of all of the above?” Fiore says. “Being able to separate human-caused impacts from natural climate variations can help to inform strategies to address climate change and air pollution.”
This research was funded, in part, by NASA.
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July’s Best Indie Games And Marvel Rivals | GI Show
In this week’s episode of The Game Informer Show, our editor-in-chief, Matt Miller, joins Alex and Marcus to discuss why Marvel Rivals has grown on us and how it’s shaking up the Overwatch formula. Next, the crew dives into some of July’s best indie games, including Dungeons of Hinterberg, Arranger, and Thank Goodness You’re Here — okay, that last one technically releases today, August 1st, but I played and beat it during July via a pre-release copy. Finally, Marcus dives into Silent Hill 2 (2001) and Forestrike, the follow-up to 2021’s pixel art action title, Olija.
Watch the Video Version on YouTube:
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Follow us on social media: Alex Van Aken (@itsVanAken), Kyle Hilliard (@KyleMHilliard), Marcus Stewart (@MarcusStewart7)
The Game Informer Show is a weekly gaming podcast covering the latest video game news, industry topics, exclusive reveals, and reviews. Join us every Thursday to chat about your favorite games – past and present – with Game Informer staff, developers, and special guests from around the industry. Listen on Apple Podcasts, Spotify, or your favorite podcast app.
The Game Informer Show – Podcast Timestamps:
00:00:00 – Intro
00:05:29 – Marvel Rivals Closed Beta
00:31:27 – Thank Goodness You’re Here!
00:41:00 – Dungeons Of Hinterberg
00:48:37 – Forestrike Preview
00:59:31 – Silent Hill 2 (2001)
01:14:27 – Arranger: A Role-Puzzling Adventure
01:21:37 – Housekeeping
A bright and airy hub for climate at MIT
Seen from a distance, MIT’s Cecil and Ida Green Building (Building 54) — designed by renowned architect and MIT alumnus I.M. Pei ’40 — is one of the most iconic buildings on the Cambridge, Massachusetts, skyline. Home to the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS), the 21-story concrete structure soars over campus, topped with its distinctive spherical radar dome. Close up, however, it was a different story.
A sunless, two-story, open-air plaza beneath the tower previously served as a nondescript gateway to the department’s offices, labs, and classrooms above. “It was cold and windy — probably the windiest place on campus,” EAPS department head Robert van der Hilst, the Schlumberger Professor of Earth and Planetary Sciences, told a packed auditorium inside the building in March. “You would pass through the elevators and disappear into the corridors, never to be seen again until the end of the day.”
Van der Hilst was speaking at a dedication event to celebrate the opening of the renovated and expanded space, 60 years after the Green Building’s original dedication in 1964. In a dramatic transformation, the perpetually-shaded expanse beneath the tower has been filled with an airy, glassed-in structure that is as inviting as the previous space was forbidding.
Designed to meet LEED-platinum certification, the newly-constructed Tina and Hamid Moghadam Building (Building 55) seems to float next to the Brutalist tower, its glass façade both opening up the interior and reflecting the sunlight and green space outside. The 300-seat auditorium within the original tower has been similarly transformed, bringing light and space to the newly dubbed Dixie Lee Bryant (1891) Lecture Hall, named after the first person to earn a geology degree at MIT.
Catalyzing collaboration
The project is about more than updating an overlooked space. “The building we’re here to celebrate today does something else,” MIT President Sally Kornbluth said at the dedication.
“In its lightness, in its transparency, it calls attention not to itself, but to the people gathered inside it. In its warmth, its openness, it makes room for culture and community. And it welcomes in those who don’t yet belong … as we take on the immense challenges of climate together,” she continued, referencing the recent launch of The Climate Project at MIT — a whole-of-MIT initiative to innovate bold solutions to climate change. In MIT’s famously decentralized structure, the Moghadam Building provides a new physical hub for students, scientists, and engineers interested in climate and the environment to congregate and share ideas.
From the start, fostering this kind of multidisciplinary collaboration was part of Van der Hilst’s vision. In addition to serving as the flagship location for EAPS, Building 54 has long been the administrative home of the MIT-WHOI Joint Program in Oceanography/Applied Ocean Science and Engineering — a graduate program in partnership with Woods Hole Oceanographic Institute. With the addition of Building 55, EAPS has now been joined by the MIT Environmental Solutions Initiative (ESI) — a campus-wide program fostering education, outreach, and innovation in earth system science, urban infrastructure, and sustainability — and will welcome closer collaboration with Terrascope — a first-year learning community which invites its students to take on real-world environmental challenges.
A shared vision comes to life
The building project dovetailed with the long-overdue refurbishment of the Green Building. After a multi-year fundraising campaign where Van der Hilst spearheaded the department’s efforts, the project received a major boost from lead donors Tina and Hamid Moghadam ’77, SM ’78, allowing the department to break ground in November 2021.
In Moghadam, chair and CEO of Prologis, which owns 1.2 billion square feet of warehouses and other logistics infrastructure worldwide, EAPS found a fellow champion for climate and environmental innovation. By putting solar panels on the roofs of Prologis buildings, the company is now the second largest on-site producer of solar energy in the United States. “I don’t think there needs to be a trade-off between good sound economics and return on investment and solving climate change problems,” Moghadam said at the dedication. “The solutions that really work are the ones that actually make sense in a market economy.”
Architectural firm AW-ARCH designed the Moghadam Building with a light touch, emphasizing spaciousness in contrast to the heavy concrete buildings that surround it. “The kind of delicacy and fragility of the thing is in some ways a depiction of what happens here,” said architect and co-founding partner Alex Anmahian at the dedication reception, giving a nod to the study of the delicate balance of the earth system itself. The sense is further illustrated by the responsiveness of the façade to the surrounding environment, which, depending on the time of day and quality of light, makes the glass alternately reflective and transparent.
Inside, the 11,900-square foot pavilion is highly flexible and serves as a showcase for the science that happens in the labs and offices above. Central to the space is a 16-foot by 9-foot video wall featuring vivid footage of field work, lab research, data visualizations, and natural phenomena — visible even to passers-by outside. The video wall is counterposed to an unpretentious set of stair-step bleachers leading to the second floor that could play host to anything from a scientific lecture to a community pizza-and-movie night.
Van der Hilst has referred to his vision for the atrium as a “campus living room,” and the furniture throughout is intentionally chosen to allow for impromptu rearrangements, providing a valuable public space on campus for students to work and socialize.
The second level is similarly adaptable, featuring three classrooms with state-of-the-art teaching technologies that can be transformed from a single large space for a hackathon to intimate rooms for discussion.
“The space is really meant for a yet unforeseen experience,” Anmahian says. “The reason it is so open is to allow for any possibility.”
The inviting, dynamic design of the pavilion has also become an instant point of pride for the building’s inhabitants. At the dedication, School of Science dean Nergis Mavalvala quipped that anyone walking into the space “gains two inches in height.”
Van der Hilst quoted a colleague with a similar observation: “Now, when I come into this space, I feel respected by it.”
The perfect complement
Another significant feature of the project is the List Visual Arts Center Percent-for-Art Program installation by conceptual artist Julian Charrière, entitled “Everything Was Forever Until It Was No More.”
Consisting of three interrelated works, the commission includes: “Not All Who Wander Are Lost,” three glacial erratic boulders which sit atop their own core samples in the surrounding green space; “We Are All Astronauts,” a trio of glass pillars containing vintage globes with distinctions between nations, land, and sea removed; and “Pure Waste,” a synthetic diamond embedded in the foundation, created from carbon captured from the air and the breath of researchers who work in the building.
Known for themes that explore the transformation of the natural world over time and humanity’s complex relationship with our environment, Charrière was a perfect fit to complement the new Building 55 — offering a thought-provoking perspective on our current environmental challenges while underscoring the value of the research that happens within its walls.
School of Humanities, Arts, and Social Sciences welcomes nine new faculty
Dean Agustín Rayo and the School of Humanities, Arts, and Social Sciences recently welcomed nine new professors to the MIT community. They arrive with diverse backgrounds and vast knowledge in their areas of research.
Sonya Atalay joins the Anthropology Section as a professor. She is a public anthropologist and archaeologist who studies Indigenous science protocols, practices, and research methods carried out with and for Indigenous communities. Atalay is the director and principal investigator of the Center for Braiding Indigenous Knowledges and Science, a newly established National Science Foundation Science and Technology Center. She has expertise in the Native American Graves Protection and Repatriation Act (NAGPRA) and served two terms on the National NAGPRA Review Committee, first appointed by the Bush administration and then for a second term by the Obama administration. Atalay has produced a series of research-based comics in partnership with Native nations about repatriation of Native American ancestral remains, return of sacred objects and objects of cultural patrimony under NAGPRA law. Atalay earned her PhD in anthropology from the University of California at Berkeley (UC Berkeley).
Anna Huang SM ’08 joins the departments of Electrical Engineering and Computer Science (EECS) and Music and Theater Arts as assistant professor. She will help develop graduate programming focused on music technology. Previously, she spent eight years with Magenta at Google Brain and DeepMind, spearheading efforts in generative modeling, reinforcement learning, and human-computer interaction to support human-AI partnerships in music-making. She is the creator of Music Transformer and Coconet (which powered the Bach Google Doodle). She was a judge and organizer for the AI Song Contest. Anna holds a Canada CIFAR AI Chair at Mila, a BM in music composition, a BS in computer science from the University of Southern California, an MS from the MIT Media Lab, and a PhD from Harvard University.
Elena Kempf joins the History Section as an assistant professor. She is an historian of modern Europe with special interests in international law and modern Germany in its global context. Her current book project is a legal, political, and cultural history of weapons prohibitions in modern international law from the 1860s to the present. Before joining MIT, Kempf was a postdoc at the Miller Institute for Global Challenges and the Law at UC Berkeley and a lecturer at the Department of History at Stanford University. Elena earned her PhD in history from UC Berkeley.
Matthias Michel joins the Department of Linguistics and Philosophy as an assistant professor. Matthias completed his PhD in philosophy in 2019 at Sorbonne Université. Before coming to MIT, he was a Bersoff Faculty Fellow in the Department of Philosophy at New York University. His research is at the intersection between philosophy and cognitive science, and focuses on philosophical issues related to the scientific study of consciousness. His current work addresses questions such as how to distinguish entities with minds from those without, which animals are sentient, and which mental functions can be performed unconsciously.
Jacob Moscona PhD ’21 is a new assistant professor in the Department of Economics. His research explores broad questions in economic development, with a focus on the role of innovation, the environment, and political economy. One stream of his research investigates the forces that drive the rate and direction of technological progress, as well as how new technologies shape global productivity differences and adaptation to major threats like climate change. Another stream of his research studies the political economy of economic development, with a focus on how variation in social organization and institutions affects patterns of conflict and cooperation. Prior to joining MIT, he was a Prize Fellow in Economics, History, and Politics at Harvard University. He received his BA from Harvard in 2016 and PhD from MIT in 2021. Outside of MIT, Jacob enjoys playing and performing music.
Sendhil Mullainathan joins the departments of EECS and Economics as the Peter de Florez Professor. His research uses machine learning to understand complex problems in human behavior, social policy, and medicine. Previously, Mullainathan spent five years at MIT before joining the faculty at Harvard in 2004, and then the University of Chicago in 2018. He received his BA in computer science, mathematics, and economics from Cornell University and his PhD from Harvard.
Elise Newman PhD ’21 is a new assistant professor in the Department of Linguistics and Philosophy. Her forthcoming monograph, “When arguments merge,” studies the ingredients that languages use to construct verb phrases, and examines how those ingredients interact with other linguistic processes such as question formation. By studying these interactions, she forms a hypothesis about how different languages’ verb phrases can be distinct from each other, and what they must have in common, providing insight into this aspect of the human language faculty. In addition to the structural properties of language, Newman also has expertise in semantics (the study of meaning) and first language acquisition. She returns to MIT after a postdoc at the University of Edinburgh, after completing her PhD in linguistics at MIT in 2021.
Oliver Rollins joins the Program in Science, Technology, and Society as an assistant professor. He is a qualitative sociologist who explores the sociological dimensions of neuroscientific knowledge and technologies. His work primarily illustrates the way race, racialized discourses, and systemic practices of social difference impact and are shaped by the development and use of neuroscience. His book, “Conviction: The Making and Unmaking of The Violent Brain” (Stanford University Press, 2021), traces the evolution of neuroimaging research on antisocial behavior, stressing the limits of this controversial brain model when dealing with aspects of social inequality. Rollins’s second book project will grapple with the legacies of scientific racism in and through the mind and brain sciences, elucidating how the haunting presence of race endures through modern neuroscientific theories, data, and technologies. Rollins recently received an NSF CAREER Award to investigate the intersections between social justice and science. Through this project, he aims to examine the sociopolitical vulnerabilities, policy possibilities, and anti-racist promises for contemporary (neuro)science.
Ishani Saraf joins the Program in Science, Technology, and Society as an assistant professor. She is a sociocultural anthropologist. Her research studies the transformation and trade of discarded machines in translocal spaces in India and the Indian Ocean, where she focuses on questions of postcolonial capitalism, urban belonging, material practices, situated bodies of knowledge, and environmental governance. She received her PhD from the University of California at Davis, and prior to joining MIT, she was a postdoc and lecturer at the University of Virginia.
From large labs to small teams, mentorship thrives
Each year, new MIT graduate students are tasked with the momentous decision of choosing a research group that will serve as their home for the next several years. Among many questions they face: join an established research effort, or work with a new faculty member in a growing group?
Professors Cynthia Breazeal, leading a group of over 30 students, and Ming Guo, with a lab of fewer than 10, demonstrate that excellent mentorship can thrive in a research group of any size.
Cynthia Breazeal: Flexible leadership
Cynthia Breazeal is a professor of media arts and sciences at MIT, where she founded and directs the Personal Robots group at the MIT Media Lab. She is also the MIT dean for digital learning, leading MIT Open Learning’s business and research and engagement units. Breazeal is a pioneer of social robotics and human-robot interaction, and her research group investigates social robots applied to education, pediatrics, health and wellness, and aging.
Breazeal’s focus on taking multidisciplinary approaches to her research has resulted in an inclusive and supportive lab environment. Moreover, she does not shy away from taking students with unconventional backgrounds.
One nominator joined Breazeal’s lab as a design researcher without a computer science background. However, Breazeal recognized the value of their work within the context of her lab’s research directions. “I was a bit of an oddball in the group”, the nominator modestly recounts, “but had joined to help make the work in the group more human-centered.”
Throughout the student’s academic journey, Breazeal offered unwavering support, whether by connecting them with experts to solve specific problems or guiding them through the academic job search process.
Over the Covid-19 pandemic, Breazeal prioritized gathering student feedback through a survey about how she could best support her research group. In response to this input, Breazeal established the Senior Research Team (SRT) within her group.
The SRT includes PhD holders such as postdocs and research scientists who provide personalized mentorship to one or two graduate students per semester. The SRT members serve as dedicated advocates and points of contact, with weekly check-ins to address questions within the lab. Additionally, SRT members meet by themselves weekly to discuss student concerns and bring up urgent issues with Breazeal directly. Lastly, students can sign up for meetings with Breazeal and participate in paper review sessions with her and co-authors.
In the nominator’s opinion, this new system was implemented because Breazeal cares about her students and her lab culture. With over 30 members in her group, Breazeal cannot provide hands-on support for everyone daily, but she still deeply cares about each person’s experience in the lab. The nominator shared that Breazeal “understands as she progresses in her career, she needs to make sure that she is changing and creating new systems for her research group to continue to operate smoothly.”
Ming Guo: Emphasizing learning over achievement
Ming Guo is an associate professor in the Department of Mechanical Engineering. Guo’s group works at the interface of mechanics, physics, and cell biology, seeking to understand how physical properties and biological function affect each other in cellular systems.
A key aspect of Guo’s mentorship style is his ability to foster an environment where students feel comfortable expressing their difficulties. He actively shows empathy for his students’ lives outside of the lab, often reaching out to provide support during challenging times. When one nominator found themselves faced with significant personal difficulties, Guo made a point to check in regularly, ensuring the student had a support network of friends and labmates.
Guo champions his students both academically and personally. For instance, when a collaborating lab placed unrealistic expectations on a student’s experimental output, Guo openly praised the student’s efforts and achievements in a joint meeting, alleviating pressure and highlighting the student’s hard work.
In addition, Guo encourages vulnerable conversations about issues affecting students, such as political developments and racial inequities. During the graduate student unionization process, he fostered open discussion, showing genuine interest in understanding the challenges faced by graduate students and using these insights to better support them.
In Guo’s research group, learning and development are prioritized over achievements and goals. When students encounter challenges in their research, Guo helps them maintain perspective by validating their struggles and recognizing the skills they acquire through difficult experiments. By celebrating their progress and emphasizing the importance of the learning process, he ensures that students understand the value of their experiences beyond outcomes. This approach not only boosts their confidence, but also fosters a deeper appreciation for the scientific process and their own development as researchers.
Guo says that he feels most energized and happy when he talks to students. He looks forward to the new ideas that they present. One nominator commented on how much Guo enjoys giving feedback at group meetings: “Sometimes he isn’t convinced in the beginning, but he has cultivated our lab atmosphere to be conducive to extended discussion.”
The nominator continues, “When things do work and become really interesting, he is extremely excited with us and pushes us to share our own ideas with the wider research community.”
Physicists report new insights into exotic particles key to magnetism
MIT physicists and colleagues report new insights into exotic particles key to a form of magnetism that has attracted growing interest because it originates from ultrathin materials only a few atomic layers thick. The work, which could impact future electronics and more, also establishes a new way to study these particles through a powerful instrument at the National Synchrotron Light Source II at Brookhaven National Laboratory.
Among their discoveries, the team has identified the microscopic origin of these particles, known as excitons. They showed how they can be controlled by chemically “tuning” the material, which is primarily composed of nickel. Further, they found that the excitons propagate throughout the bulk material instead of being bound to the nickel atoms.
Finally, they proved that the mechanism behind these discoveries is ubiquitous to similar nickel-based materials, opening the door for identifying — and controlling — new materials with special electronic and magnetic properties.
The open-access results are reported in the July 12 issue of Physical Review X.
“We’ve essentially developed a new research direction into the study of these magnetic two-dimensional materials that very much relies on an advanced spectroscopic method, resonant inelastic X-ray scattering (RIXS), which is available at Brookhaven National Lab,” says Riccardo Comin, MIT’s Class of 1947 Career Development Associate Professor of Physics and leader of the work. Comin is also affiliated with the Materials Research Laboratory and the Research Laboratory of Electronics.
Comin’s colleagues on the work include Connor A. Occhialini, an MIT graduate student in physics, and Yi Tseng, a recent MIT postdoc now at Deutsches Elektronen-Synchrotron (DESY). The two are co-first authors of the Physical Review X paper.
Additional authors are Hebatalla Elnaggar of the Sorbonne; Qian Song, a graduate student in MIT’s Department of Physics; Mark Blei and Seth Ariel Tongay of Arizona State University; Frank M. F. de Groot of Utrecht University; and Valentina Bisogni and Jonathan Pelliciari of Brookhaven National Laboratory.
Ultrathin layers
The magnetic materials at the heart of the current work are known as nickel dihalides. They are composed of layers of nickel atoms sandwiched between layers of halogen atoms (halogens are one family of elements), which can be isolated to atomically thin layers. In this case, the physicists studied the electronic properties of three different materials composed of nickel and the halogens chlorine, bromine, or iodine. Despite their deceptively simple structure, these materials host a rich variety of magnetic phenomena.
The team was interested in how these materials’ magnetic properties respond when exposed to light. They were specifically interested in particular particles — the excitons — and how they are related to the underlying magnetism. How exactly do they form? Can they be controlled?
Enter excitons
A solid material is composed of different types of elementary particles, such as protons and electrons. Also ubiquitous in such materials are “quasiparticles” that the public is less familiar with. These include excitons, which are composed of an electron and a “hole,” or the space left behind when light is shone on a material and energy from a photon causes an electron to jump out of its usual position.
Through the mysteries of quantum mechanics, however, the electron and hole are still connected and can “communicate” with each other through electrostatic interactions. This interaction leads to a new composite particle formed by the electron and the hole — an exciton.
Excitons, unlike electrons, have no charge but possess spin. The spin can be thought of as an elementary magnet, in which the electrons are like little needles orienting in a certain way. In a common refrigerator magnet, the spins all point in the same direction. Generally speaking, the spins can organize in other patterns leading to different kinds of magnets. The unique magnetism associated with the nickel dihalides is one of these less-conventional forms, making it appealing for fundamental and applied research.
The MIT team explored how excitons form in the nickel dihalides. More specifically, they identified the exact energies, or wavelengths, of light necessary for creating them in the three materials they studied.
“We were able to measure and identify the energy necessary to form the excitons in three different nickel halides by chemically ‘tuning,’ or changing, the halide atom from chlorine to bromine to iodine,” says Occhialini. “This is one essential step towards understanding how photons — light — could one day be used to interact with or monitor the magnetic state of these materials.” Ultimate applications include quantum computing and novel sensors.
The work could also help predict new materials involving excitons that might have other interesting properties. Further, while the studied excitons originate on the nickel atoms, the team found that they do not remain localized to these atomic sites. Instead, “we showed that they can effectively hop between sites throughout the crystal,” Occhialini says. “This observation of hopping is the first for these types of excitons, and provides a window into understanding their interplay with the material’s magnetic properties.”
A special instrument
Key to this work — in particular for observing the exciton hopping — is resonant inelastic X-ray scattering (RIXS), an experimental technique that co-authors Pelliciari and Bisogni helped pioneer. Only a few facilities in the world have advanced high energy resolution RIXS instruments. One is at Brookhaven. Pelliciari and Bisogni are part of the team running the RIXS facility at Brookhaven. Occhialini will be joining the team there as a postdoc after receiving his MIT PhD.
RIXS, with its specific sensitivity to the excitons from the nickel atoms, allowed the team to “set the basis for a general framework for nickel dihalide systems,” says Pelliciari. “it allowed us to directly measure the propagation of excitons.”
This work was supported by the U.S. Department of Energy Basic Energy Science and Brookhaven National Laboratory through the Co-design Center for Quantum Advantage (C2QA), a DoE Quantum Information Science Research Center.
Here’s The First Trailer For Amazon’s Like A Dragon Series
Last month, we learned Sega and Amazon had partnered to create a live-action series based on the Like a Dragon (formerly Yakuza) series. Over the weekend, during the San Diego Comic-Con, the studio unveiled the first teaser trailer.
Like A Dragon: Yakuza centers on Kazuma Kiryu (played by Takeuchi Ryoma) and follows his life during two time periods: 1995 and 2005. Set in the series’ fictional Tokyo district of Kamurochō, the trailer’s synopsis states the show “depicts the lives of fierce yet passionate gangsters and people” and will explore stories the games haven’t been able to.
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The six-episode series will be released on Prime Video in two parts, with the first three episodes premiering on October 24 and the last three arriving on November 1. It will be subbed and dubbed in 30 languages. Like a Dragon: Yakuza is directed by Take Masaharu (100 Yen Love).
You can read our review of the latest game in the series, Like a Dragon: Infinite Wealth, here.