Capybaras like their habitats wet. These large rodents thrive in low-elevation wetlands, migrating along creeks and rivers to nibble on foliage and flowers. That’s why researchers were surprised to find an 8.8 million-year-old fossilized capybara tooth in northern Chile’s , one of the driest regions on Earth. In a paper in Scientific Reports, researchers postulate that the Atacama Desert must have had a wetter climate during the , based on this discovery. This is the first time a capybara species has ever been seen in the Atacama region of Chile 鈥� today these creatures reside in the marshy lowlands across Venezuela, Colombia, Argentina and Uruguay. Researchers had at one time assumed that the Andean mountain chain on the eastern side of Chile would have prevented these short-legged rodents from ever entering the Atacama region. With this discovery, the authors propose that capybaras were able to follow a wetland trail along the northern part of South America, trekking from Bolivia to Peru into northern Chile. In addition to capybaras, the ancient Atacama region also likely had palms and other flowering plants, according to plant fossils analyzed by a UW scientist for the study. These findings challenge the idea that the Atacama was just always a desert, and can help researchers better understand how shifts in climate can drastically affect the environment.

For more information, contact co-author , UW professor of biology, at caestrom@uw.edu.听听听听听听

A full list of co-authors and funding is . Adapted from a release .

Multitasking gives marine microbes an edge when nutrients are scarce

The world鈥檚 oceans teem with tiny organisms that are difficult to study yet critical to account for. The organisms that make up this microscopic community, many of which are protists, have evolved over time to help keep marine ecosystems balanced. A UW study in the ISME Journal, found that organisms that can both photosynthesize and eat to generate energy do better in nutrient-limited environments, which includes warmer water. This flexibility may help them cope with changing conditions and could help researchers gauge how marine ecosystems will respond to future warming. Gathering more data from the bottom of the food web is important for understanding the ecosystem-wide impacts of environmental change. The study also debuted a new genetic method for studying energy production versus consumption that may make it easier to study protists. Samples in this study were collected from the North Pacific, near Hawaii and about 1,000 miles north, but the researchers hope to continue expanding the radius to improve global ocean models.

For more information, contact , UW research scientist and engineer of biological oceanography at coesel@uw.edu.

The UW co-authors are Shiri Graff van Creveld, and . A full list of co-authors and funding is .

UW engineers capture behavior of ‘edge waves’ on beaches, putting popular wave models to the test

Coastal engineers and oceanographers often think of the motion of water on beaches as “one dimensional”: waves propagating directly onto the beach from offshore. These simplified wave models are used widely from designing shoreline infrastructure to forecasting coastal flooding. However, some waves propagate along the coast rather than crashing into it, and may push an additional meter of water depth onto the beach. For decades, these “edge waves” have not been accounted for in the one-dimensional models commonly used to understand wave behavior. To find out how edge waves might be impacting model accuracy, researchers at the UW and UC San Diego deployed an array of pressure and velocity sensors along a beach in Southern California for 60 days. In a paper in JGR Oceans, the researchers describe a model they built to tease out the influence of edge waves in the larger system. While edge waves contributed a significant amount of energy, the team found that ultimately the one-dimensional models that exclude edge waves remain accurate enough for predicting total water levels at the shoreline.

For more information, contact , a postdoctoral scholar of civil and environmental engineering, at cshender@uw.edu.

A full list of co-authors and funding is .

How Colombian environmentalists use law and democracy to redefine mountain landscapes

In 2013 and 2017, Colombian voters in two towns backed a legal effort to stop a large-scale gold mining project. In doing so, they are making the mountainous areas where they live more visible and politically relevant. The decision allowed environmental advocates to organize around a larger area defined by elevation, massive volume, and subterranean and arboreal features. , UW assistant professor of anthropology, a research article in the journal Anthropological Forum that examines how the effort used legal tools for citizen participation to not only voice their opinions on extractive projects, but also reconfigure space in unprecedented ways. The case shows that democratic participation can have far-reaching consequences for how landscapes are defined and lived. The article appears in a special issue, called “Ethnographies of Vertical and Volumetric Worlds,” which was co-edited by Ardila and Steven Schwartz of the University of Rochester.

For more information, contact Castillo at acastil@uw.edu.

Funding information is .

Researchers develop new way to measure how blood clots form

A wound stops bleeding because tiny blood cell fragments called platelets clump together to form a clot. Researchers know that platelets generate forces that help compact and strengthen clots. However, they鈥檝e struggled to understand how blood clots form in real time. To better understand this system, UW mechanical engineers created a device that measures how platelet forces and stiffness evolve together during the first minutes of clot formation. in Advanced Healthcare Materials, the research team used the device to apply magnetic forces to clumps of platelets, causing them to strengthen and stiffen through a process called 鈥渕echanotransduction鈥� in which cells convert mechanical forces into biological responses. These findings could be used to study how new drugs affect clot formation, how platelets respond to signals when disease is present, and how blood clotting biomechanics contribute to cardiovascular disorders.

For more information, contact , a UW professor of mechanical engineering, at nsniadec@uw.edu.

The UW co-authors are , , Yoeur-Man Mach and . A full list of co-authors and funding is . Adapted from a story by .

UW researchers probe superconducting materials that defy expectations

Most materials resist the flow of electricity to some degree, but unusual materials known as superconductors can carry an electric current with no resistance at all. Superconductors offer a unique window into the physics of materials at tiny scales, and they could one day revolutionize electronics. In recent years, researchers have discovered new forms of superconductivity in stacks of atomically thin materials such as . Resistance typically drops to zero as these materials are cooled, but in some cases it mysteriously levels off at a small finite value, which contradicts expectations of superconductor behavior. In a paper in Nature, UW materials scientists tested this behavior with a device consisting of several layers of graphene stacked in a staircase-like pattern. By adjusting voltages applied to the device, the researchers could control whether the graphene exhibited true superconductivity or the more peculiar 鈥渇ailed鈥� form, providing clear evidence that failed superconductivity is real. The team is now working to uncover the origin of this mysterious behavior.

For more information, contact , a UW associate professor of both physics and materials science and engineering, at myank@uw.edu..

The UW co-authors are , , and . A full list of co-authors and funding is .

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For decades, scientists have been probing the potential of two-dimensional materials to transform our world. 2D materials are only a single layer of atoms thick. Within them, subatomic particles like electrons can only move in two dimensions. This simple restriction can trigger unusual electron behavior, imbuing the materials with 鈥渆xotic鈥� properties like bizarre forms of magnetism, superconductivity and other collective behaviors among electrons 鈥� all of which could be useful in computing, communication, energy and other fields.

But researchers have generally assumed that these exotic 2D properties exist only in single-layer sheets, or short stacks. The so-called 鈥渂ulk鈥� versions of these materials 鈥� with their more complex 3D atomic structures 鈥� should behave differently.

Or so they thought.

In a published July 19 in Nature, a team led by researchers at the 天美影视传媒 reports that it is possible to imbue graphite 鈥� the bulk, 3D material found in No. 2 pencils 鈥� with physical properties similar to graphite鈥檚 2D counterpart, graphene. Not only was this breakthrough unexpected, the team also believes its approach could be used to test whether similar types of bulk materials can also take on 2D-like properties. If so, 2D sheets won鈥檛 be the only source for scientists to fuel technological revolutions. Bulk, 3D materials could be just as useful.

鈥淪tacking single layer on single layer 鈥� or two layers on two layers 鈥� has been the focus for unlocking new physics in 2D materials for several years now. In these experimental approaches, that鈥檚 where many interesting properties emerge,鈥� said senior author , a UW assistant professor of physics and of materials science and engineering. 鈥淏ut what happens if you keep adding layers? Eventually it has to stop, right? That鈥檚 what intuition suggests. But in this case, intuition is wrong. It鈥檚 possible to mix 2D properties into 3D materials.鈥�

The team, which also includes researchers at Osaka University and the National Institute for Materials Science in Japan, adapted an approach commonly used to probe and manipulate the properties of 2D materials: stacking 2D sheets together at a small twist angle. Yankowitz and his colleagues placed a single layer of graphene on top of a thin, bulk graphite crystal, and then introduced a twist angle of around 1 degree between graphite and graphene. They detected novel and unexpected electrical properties not just at the twisted interface, but deep in the bulk graphite as well.

The twist angle is critical to generating these properties, said Yankowitz, who is also a faculty member in the UW Clean Energy Institute and the UW Institute for Nano-Engineered Systems. A twist angle between 2D sheets, like two sheets of graphene, creates what鈥檚 called a moir茅 pattern, which alters the flow of charged particles like electrons and induces exotic properties in the material.

In the UW-led experiments with graphite and graphene, the twist angle also induced a moir茅 pattern, with surprising results. Even though only a single sheet of graphene atop the bulk crystal was twisted, researchers found that the electrical properties of the whole material differed markedly from typical graphite. And when they turned on a magnetic field, electrons deep in the graphite crystal adopted unusual properties similar to those of electrons at the twisted interface. Essentially, the single twisted graphene-graphite interface became inextricably mixed with the rest of the bulk graphite.

鈥淭hough we were generating the moir茅 pattern only at the surface of the graphite, the resulting properties were bleeding across the whole crystal,鈥� said co-lead author , a UW postdoctoral researcher in physics.

For 2D sheets, moir茅 patterns generate properties that could be useful for quantum computing and other applications. Inducing similar phenomena in 3D materials unlocks new approaches for studying unusual and exotic states of matter and how to bring them out of the laboratory and into our everyday lives.

鈥淭he entire crystal takes on this 2D state,鈥� said co-lead author Ellis Thompson, a UW doctoral student in physics. 鈥淭his is a fundamentally new way to affect electron behavior in a bulk material.鈥�

Yankowitz and his team believe their approach of generating a twist angle between graphene and a bulk graphite crystal could be used to create 2D-3D hybrids of its sister materials, including tungsten ditelluride and zirconium pentatelluride. This could unlock a new approach to re-engineering the properties of conventional bulk materials using a single 2D interface.

鈥淭his method could become a really rich playground for studying exciting new physical phenomena in materials with mixed 2D and 3D properties,鈥� said Yankowitz.

Co-authors on paper are UW graduate student Esmeralda Arreguin-Martinez and UW postdoctoral researcher Yafei Ren, both in the Department of Materials Science and Engineering; , a UW assistant professor of materials science and engineering; , a UW professor of physics and chair of materials science and engineering; Manato Fujimoto of Osaka University; and Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Japan. The research was funded by the National Science Foundation; the U.S. Department of Energy; the UW Clean Energy Institute; the Office of the Director of National Intelligence; the Japan Science and Technology Agency; the Japan Society for the Promotion of Science; the Japanese Ministry of Education, Culture, Sports, Science and Technology; and the M.J. Murdock Charitable Trust.

For more information, contact Yankowitz at myank@uw.edu.

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Scientists can have ambitious goals: curing disease, exploring distant worlds, clean-energy revolutions. In physics and materials research, some of these ambitious goals are to make ordinary-sounding objects with extraordinary properties: wires that can transport power without any energy loss, or quantum computers that can perform complex calculations that today鈥檚 computers cannot achieve. And the emerging workbenches for the experiments that gradually move us toward these goals are 2D materials 鈥� sheets of material that are a single layer of atoms thick.

In a published Sept. 14 in the journal Nature Physics, a team led by the 天美影视传媒 reports that carefully constructed stacks of graphene 鈥� a 2D form of carbon 鈥� can exhibit highly correlated electron properties. The team also found evidence that this type of collective behavior likely relates to the emergence of exotic magnetic states.

鈥淲e鈥檝e created an experimental setup that allows us to manipulate electrons in the graphene layers in a number of exciting new ways,鈥� said co-senior author , a UW assistant professor of physics and of materials science and engineering, as well as a faculty researcher at the UW聽.

Yankowitz led the team with co-senior author , a UW professor of physics and of materials science and engineering. Xu is also a faculty researcher with the UW , the UW and the Clean Energy Institute.

Since 2D materials are one layer of atoms thick, bonds between atoms only form in two dimensions and particles like electrons can only move like pieces on a board game: side-to-side, front-to-back or diagonally, but not up or down. These restrictions can imbue 2D materials with properties that their 3D counterparts lack, and scientists have been probing 2D sheets of different materials to characterize and understand these potentially useful qualities.

But over the past decade, scientists like Yankowitz have also started layering 2D materials 鈥� like a stack of pancakes 鈥� and have discovered that, if stacked and rotated in a particular configuration and exposed to extremely low temperatures, these layers can exhibit exotic and unexpected properties.

The UW team worked with building blocks of bilayer graphene: two sheets of graphene naturally layered together. They stacked one bilayer on top of another 鈥� for a total of four graphene layers 鈥� and twisted them so that the layout of carbon atoms between the two bilayers were slightly out of alignment. Past research has shown that introducing these small twist angles between single layers or bilayers of graphene can have big consequences for the behavior of their electrons. With specific configurations of the electric field and charge distribution across the stacked bilayers, electrons display highly correlated behaviors. In other words, they all start doing the same thing 鈥� or displaying the same properties 鈥� at the same time.

鈥淚n these instances, it no longer makes sense to describe what an individual electron is doing, but what all electrons are doing at once,鈥� said Yankowitz.

鈥淚t鈥檚 like having a room full of people in which a change in any one person鈥檚 behavior will cause everyone else to react similarly,鈥� said lead author , a UW doctoral student in physics and a former Clean Energy Institute fellow.

Quantum mechanics underlies these correlated properties, and since the stacked graphene bilayers have a density of more than 10¹², or one trillion, electrons per square centimeter, a lot of electrons are behaving collectively.

The team sought to unravel some of the mysteries of the correlated states in their experimental setup. At temperatures of just a few degrees above absolute zero, the team discovered that they could 鈥渢une鈥� the system into a type of correlated insulating state 鈥� where it would conduct no electrical charge. Near these insulating states, the team found pockets of highly conducting states with features resembling superconductivity.

Though other teams have recently reported these states, the origins of these features remained a mystery. But the UW team鈥檚 work has found evidence for a possible explanation. They found that these states appeared to be driven by a quantum mechanical property of electrons called 鈥渟pin鈥� 鈥� a type of angular momentum. In regions near the correlated insulating states, they found evidence that all the electron spins spontaneously align. This may indicate that, near the regions showing correlated insulating states, a form of is emerging 鈥� not superconductivity. But additional experiments would need to verify this.

These discoveries are the latest example of the many surprises that are in store when conducting experiments with 2D materials.

鈥淢uch of what we鈥檙e doing in this line of research is to try to create, understand and control emerging electronic states, which can be either correlated or topological, or possess both properties,鈥� said Xu. 鈥淭here could be a lot we can do with these states down the road 鈥� a form of quantum computing, a new energy-harvesting device, or some new types of sensors, for example 鈥� and frankly we won鈥檛 know until we try.鈥�

In the meantime, expect stacks, bilayers and twist angles to keep making waves.

Co-authors are UW researchers Yuhao Li and Yang Liu; UW physics doctoral student and Clean Energy Institute fellow Jiaqi Cai; and K. Watanabe and T. Taniguchi with the National Institute for Materials Science in Japan. The research was funded by the UW Molecular Engineering Materials Center, a National Science Foundation Materials Research Science and Engineering Center; the China Scholarship Council; the Ministry of Education, Culture, Sports, Science and Technology of Japan; and the Japan Science and Technology Agency.

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For more information, contact Xu at xuxd@uw.edu and Yankowitz at myank@uw.edu.

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