To achieve this, we need so-called quantum materials: substances that exhibit pronounced quantum physical effects. One such material is graphene. This two-dimensional structural form of carbon has unusual physical properties, such as extraordinarily high tensile strength, thermal and electrical conductivity — as well as certain quantum effects. Restricting the already two-dimensional material even further, for instance, by giving it a ribbon-like shape, gives rise to a range of controllable quantum effects.

This is precisely what Mickael Perrin’s team leverage in their work: For several years now, scientists in Empa’s Transport at Nanoscale Interfaces laboratory, headed by Michel Calame, have been conducting research on graphene nanoribbons under Perrin’s leadership. “Graphene nanoribbons are even more fascinating than graphene itself,” explains Perrin. “By varying their length and width, as well as the shape of their edges, and by adding other atoms to them, you can give them all kinds of electrical, magnetic, and optical properties.”

Ultimate precision — down to single atoms

Research on the promising ribbons isn’t easy. The narrower the ribbon, the more pronounced its quantum properties are — but it also becomes more difficult to access a single ribbon at a time. This is precisely what must be done in order to understand the unique characteristics and possible applications of this quantum material and distinguish them from collective effects.

In a new study published recently in the journal Nature Electronics, Perrin and Empa researcher Jian Zhang, together with an international team, have succeeded for the first time in contacting individual long and atomically precise graphene nanoribbons. Not a trivial task: “A graphene nanoribbon that is just nine carbon atoms wide measures as little as 1 nanometer in width,” Zhang says. To ensure that only a single nanoribbon is contacted, the researchers employed electrodes of a similar size: They used carbon nanotubes that were also only 1 nanometer in diameter.

Precision is key for such a delicate experiment. It begins with the source materials. The researchers obtained the graphene nanoribbons via a strong and long-standing collaboration with Empa’s nanotech surfaces laboratory, headed by Roman Fasel. “Roman Fasel and his team have been working on graphene nanoribbons for a long time and can synthesize many different types with atomic precision from individual precursor molecules,” Perrin explains. The precursor molecules came from the Max Planck Institute for Polymer Research in Mainz.

As is often required for advancing the state of the art, interdisciplinarity is key, and different international research groups were involved, each bringing in their own specialty to the table: The carbon nanotubes were grown by a research group at Peking University, and to interpret the results of the study, the Empa researchers collaborated with computational scientists at the University of Warwick. “A project like this would not be possible without collaboration,” Zhang emphasizes.

Contacting individual ribbons by nanotubes posed a considerable challenge for the researchers. “The carbon nanotubes and the graphene nanoribbons are grown on separate substrates,” Zhang explains. “First, the nanotubes need to be transferred to the device substrate and contacted by metal electrodes. Then we cut them with high-resolution electron-beam lithography to separate them into two electrodes.” Finally, the ribbons are transferred onto the same substrate. Precision is key: Even the slightest rotation of the substrates can significantly reduce the probability of successful contact. “Having access to high-quality infrastructure at the Binnig and Roher Nanotechnology Center at IBM Research in Rüschlikon was essential to test and implement this technology,” Perrin says.

From computers to energy converters

The scientists confirmed the success of their experiment through charge transport measurements. “Because quantum effects are usually more pronounced at low temperature, we performed the measurements at temperatures close to absolute zero in a high vacuum,” Perrin explains. But he is quick to add yet another particularly promising quality of graphene nanoribbons: “Due to the extremely small size of these nanoribbons, we expect their quantum effects to be so robust that they are observable even at room temperature.” This, the researcher says, could allow us to design and operate chips that actively harness quantum effects without the need for an elaborate cooling infrastructure.

“This project enables the realization of single nanoribbon devices, not only to study fundamental quantum effects such as how electrons and phonons behave at the nanoscale, but also to exploit such effects for applications in quantum switching, quantum sensing, and quantum energy conversion,” adds Hatef Sadeghi, a professor at the Univeristy of Warwick who collaborated on the project.

Graphene nanoribbons are not ready for commercial applications just yet, and there is still a lot of research to be done. In a follow-up study, Zhang and Perrin aim to manipulate different quantum states on a single nanoribbon. In addition, they plan on creating devices based on two ribbons connected in series, forming a so-called double quantum dot. Such a circuit could serve as a qubit — the smallest unit of information in a quantum computer. Moreover, Perrin, in the context of his recently obtained ERC Starting Grant and an SNSF Eccellenza Professorial Fellowship, plans to explore the use of nanoribbons as highly-efficient energy converters. In his inaugural lecture at ETH Zurich, he paints a picture of a world, in which we can harness electricity from temperature difference, while hardly losing any energy as heat — this would indeed be a real quantum leap.

The Coliseum is the size of one-and-a-half football fields and contains layer upon layer of prints preserved in rock. The site is a record of multiple species of dinosaurs over many generations that thrived in what is now Interior Alaska nearly 70 million years ago. The scientists describe the site in a paper recently published in the journal Historical Biology.

“It’s not just one level of rock with tracks on it,” said Dustin Stewart, the paper’s lead author and a former UAF graduate student who published the paper as part of his master’s thesis. “It is a sequence through time. Up until now, Denali had other track sites that are known, but nothing of this magnitude.”

At first glance, the site is unremarkable in the context of the park’s vast landscape: just a layered, rocky outcrop rising 20-some stories from its base.

“When our colleagues first visited the site, they saw a dinosaur trackway at the base of this massive cliff,” said Pat Druckenmiller, senior author of the paper and director of the University of Alaska Museum of the North. “When we first went out there, we didn’t see much either.”

Stewart recalled being initially underwhelmed when he approached the site at the end of a seven-hour hike. Then dusk approached, and the team took another look.

“When the sun angles itself perfectly with those beds, they just blow up,” he said. “Immediately all of us were just flabbergasted, and then Pat said, ‘Get your camera.’ We were freaking out.”

In the Late Cretaceous Period, the cliffs that make up The Coliseum were sediment on flat ground near what was likely a watering hole on a large flood plain. As Earth’s tectonic plates collided and buckled to form the Alaska Range, the formerly flat ground folded and tilted vertically, exposing the cliffs covered with tracks.

The tracks are a mix of hardened impressions in the ancient mud and casts of tracks created when sediment filled the tracks and then hardened.

“They are beautiful,” Druckenmiller said. “You can see the shape of the toes and the texture of the skin.”

In addition to the dinosaur tracks, the research team found fossilized plants, pollen grains, and evidence of freshwater shellfish and invertebrates.

“All these little clues put together what the environment looked like as a whole,” Stewart said.

The area was part of a large river system, he said, with ponds and lakes nearby. The climate in the area was warmer than today, more like the Pacific Northwest. There were coniferous and deciduous trees and an understory of ferns and horsetails.

Based on the tracks, a variety of juvenile to adult dinosaurs frequented the area over thousands of years. Most common were large plant-eating duck-billed and horned dinosaurs. The team also documented rarer carnivores, including raptors and tyrannosaurs, as well as small wading birds.

Every year, thousands of people visit Denali National Park and Preserve to experience the stunning natural landscape and environment, Druckenmiller said. “It’s amazing to know that around 70 million years ago, Denali was equally impressive for its flora and fauna.

“It was forested and it was teeming with dinosaurs,” he said. “There was a tyrannosaur running around Denali that was many times the size of the biggest brown bear there today. There were raptors. There were flying reptiles. There were birds. It was an amazing ecosystem.”

Preserving fossil sites like The Coliseum is an important part of the National Park Service’s mission, said Denny Capps, the park’s geologist.

“On one hand, we must protect world-class fossil sites like The Coliseum from disturbance and theft,” he said. “On the other hand, we encourage visitors to explore for fossils in their geologic context to better grasp the evolution of landscapes and ecosystems through time, while leaving them undisturbed for others to appreciate.”

Druckenmiller plans to continue collaborating with the National Park Service to study The Coliseum and other track sites.

“Our track research in the park complements our work on dinosaur bones we collect in northern Alaska, along the Colville River,” Druckenmiller said. “Denali National Park and Preserve is a world-class area for dinosaur tracks. There is a lifetime of exploring left to do, and I can only wonder what other surprises await.”