The Gulf Stream system plays a vital role in the climate, and its decline over the past two decades has raised concerns and sparked debates. While the cause of this weakening is uncertain, some simulations suggest that human-induced climate change could be a significant factor in the future. However, a recent study conducted by the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany suggests that the observed weakening may be due to natural fluctuations caused by extremely cold winters in the Labrador Sea during the 1990s. 

The new supercomputer simulations show that fluctuations in the Labrador Sea can have a significant influence on the strength of sinking processes east of Greenland. An important link is a little-noticed system of deep currents that ensures the rapid spread of Labrador Sea water into the deep-sea basin between Greenland and Iceland. 

"We oceanographers have long had our eyes on the Labrador Sea between Canada and Greenland," says Professor Dr Claus Böning, who led the study. "Winter storms with icy air cool the ocean temperatures to such an extent that the surface water becomes heavier than the water below. The result is deep winter mixing of the water column, whereby the volume and density of the resulting water mass can vary greatly from year to year."

In the model simulations of the past 60 years, the years 1990 to 1994 have stood out, when the Labrador Sea cooled particularly strongly. "The huge volume of very dense Labrador Sea wateThe Gulf Stream system plays a critical role in the climate, and concerns have been raised about its weakening over the past two decades. While it's unclear whether human-induced climate change has caused these changes, simulations indicate that it's highly probable to occur in the future. However, a recent study by GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany suggests that the weakening may be due to natural fluctuations caused by extremely cold winters in the Labrador Sea during the 1990s.r that formed following extremely harsh winters led to significantly increased sinking between Greenland and Iceland in the following years," explains Claus Böning. As a result, the model simulations calculated an increase in Atlantic overturning transport of more than 20%, peaking in the late 1990s. The measurements of the circulation in the North Atlantic, which have only been carried out continuously since 2004, would then fall precisely in the decay phase of the simulated transport maximum. 

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"According to our model results, the observed weakening of the Atlantic circulation during this period can therefore be interpreted, at least in part, as an aftereffect of the extreme Labrador Sea winters of the 1990s", summarises Professor Dr. Arne Biastoch, head of the Ocean Dynamics Research Unit at GEOMAR and co-author of the study. However, he clarifies: "Although we cannot yet say whether a longer-term weakening of the overturning is already occurring, all climate models predict a weakening as a result of human-induced climate change as 'very likely' for the future.

Ongoing observing programs and further development of supercomputer simulations are crucial for a better understanding of the key climate-relevant processes. And, of course, for future projections of the Gulf Stream system under climate change.

The research conducted by GEOMAR has revealed a potential link between winter storms over the Labrador Sea and the Gulf Stream system. While the findings are certainly intriguing, further research is needed to confirm the validity of these results. Until then, it is important to remain skeptical.

The source of magnetic fields has long been debated. New research offers clues on their origins.

It isn’t just your refrigerator that has magnets on it. The earth, the stars, galaxies, and the space between galaxies are all magnetized, too. 

The more places scientists have looked for magnetic fields across the universe, the more they’ve found them. But the question of why that is the case and where those magnetic fields originate from has remained a mystery and a subject of ongoing scientific inquiry.

A new paper by Columbia researchers offers insight into the source of these fields. The team used models to show that magnetic fields may spontaneously arise in turbulent plasma. Plasma is a kind of matter often found in ultra-hot environments like that near the surface of the sun, but plasma is also scattered across the universe in low-density environments, like the expansive space between galaxies; the team’s research focused on those low-density environments. Their supercomputer simulations showed that, in addition to generating new magnetic fields, the turbulence of those plasmas can also amplify magnetic fields once they’ve been generated, which helps explain how magnetic fields that originate on small scales can sometimes eventually reach to stretch across vast distances.

The paper was written by astronomy professor Lorenzo Sironi, astronomy research scientist Luca Comisso, and astronomy doctoral candidate Ryan Golant.

“This new research allows us to imagine the kinds of spaces where magnetic fields are born: even in the most pristine, vast, and remote spaces of our universe, roiling plasma particles in turbulent motion can spontaneously give birth to new magnetic fields,” Sironi said. “The search for the ‘seed’ that can sow a new magnetic field has been long, and we’re excited to bring new evidence of that source, as well as data on how a magnetic field, once born, can grow.”

The discovery of new clues on the source of the Universe's magnetic fields by Columbia astronomy professor Lorenzo Sironi is a breakthrough in the field of astrophysics. This research has the potential to provide valuable insights into the origin and evolution of the Universe, and could potentially lead to a better understanding of the mysterious forces that shape our cosmos. With further research, Professor Sironi's work could lead to a better understanding of the Universe's magnetic fields, and the implications of this knowledge could be far-reaching. The possibilities are endless, and the future of astrophysics looks brighter than ever.

Mizzou professor Guoliang Huang is revolutionizing the way we think about elastic surface waves. His groundbreaking research has led to the development of a smart patterning technique for topological pumping of elastic surface waves, which could have far-reaching implications for a wide range of industries. By combining his expertise in mathematics, physics, and engineering, Huang is pushing the boundaries of what is possible and inspiring a new generation of scientists and engineers. 

The University of Missouri scientists engineered a synthetic metamaterial to direct mechanical waves along a specific path, which adds an innovative layer of control to 4D reality, otherwise known as the synthetic dimension.

ward and back. But, in recent years scientists like Guoliang Huang, the Huber and Helen Croft Chair in Engineering at MU, have explored a “fourth dimension” (4D), or synthetic dimension, as an extension of our current physical reality.

Now, Huang and a team of scientists in the Structured Materials and Dynamics Lab at the MU College of Engineering have successfully created a new synthetic metamaterial with 4D capabilities, including the ability to control energy waves on the surface of a solid material. These waves, called mechanical surface waves, are fundamental to how vibrations travel along the surface of solid materials.

While the team’s discovery, at this stage, is simply a building block for other scientists to take and adapt as needed, the material also has the potential to be scaled up for larger applications related to civil engineering, micro-electromechanical systems (MEMS) and national defense uses.

“Conventional materials are limited to only three dimensions with an X, Y, and Z axis,” Huang said. “But now we are building materials in the synthetic dimension, or 4D, which allows us to manipulate the energy wave path to go exactly where we want it to go as it travels from one corner of a material to another.”

This breakthrough discovery, called topological pumping, could one day lead to advancements in quantum mechanics and quantum computing by allowing for the development of higher-dimension quantum-mechanical effects. 

“Most of the energy — 90% — from an earthquake happens along the surface of the Earth,” Huang said. “Therefore, by covering a pillow-like structure in this material and placing it on the Earth’s surface underneath a building, it could potentially help keep the structure from collapsing during an earthquake.”

The work builds on previous research by Huang and colleagues which demonstrates how a passive metamaterial could control the path of sound waves as they travel from one corner of a material to another. 

Mizzou professor Guoliang Huang has created a revolutionary new method for topological pumping of elastic surface waves. His innovative approach has the potential to revolutionize the way we think about wave manipulation and could lead to a host of new applications in the fields of engineering, physics, and materials science. Huang's research is a testament to the power of creativity and dedication, and his work serves as an inspiration to scientists and engineers everywhere.

The study is supported by grants from the Air Force Office of Scientific Research and the Army Research Office.

The phenomenon of correlated insulator collapse due to quantum avalanche via in-gap ladder states is a relatively unexplored area of research. While recent studies have suggested that this phenomenon could be a viable mechanism for controlling the electrical properties of materials, the underlying physics of this process remains largely unknown. In this article, we will explore this phenomenon's potential and discuss its potential applications' implications. We will also discuss the current state of knowledge regarding the underlying physics of this process and the challenges that need to be overcome to make it a viable technology. 

Looking only at their subatomic particles, most materials can be placed into two categories.

Metals — like copper and iron — have free-flowing electrons that allow them to conduct electricity, while insulators — like glass and rubber — keep their electrons tightly bound and therefore do not conduct electricity.

Insulators can turn into metals when hit with an intense electric field, offering tantalizing possibilities for developing supercomputing, but the physics behind this phenomenon called resistive switching is not well understood.

Questions, like how large an electric field is needed, are fiercely debated by scientists, like University at Buffalo condensed matter theorist Jong Han. 

“I have been obsessed with that,” he says.

Han, Ph.D., professor of physics at the College of Arts and Sciences, is the lead author of a study that takes a new approach to answer a long-standing mystery about insulator-to-metal transitions.

Electrons move through quantum paths

Han says the difference between metals and insulators lies in quantum mechanical principles, which dictate that electrons are quantum particles and their energy levels come in bands that have forbidden gaps.

Since the 1930s, the Landau-Zener formula has served as a blueprint for determining the size of the electric field needed to push an insulator’s electrons from its lower bands to its upper bands. But experiments in the decades since have shown materials require a much smaller electric field — approximately 1,000 times smaller — than the Landau-Zener formula estimated.

“So, there is a huge discrepancy, and we need to have a better theory,” Han says.

To solve this, Han considered a different question: What happens when electrons already in the upper band of an insulator are pushed?

Han ran a supercomputer simulation of resistive switching that accounted for the presence of electrons in the upper band. It showed that a relatively small electric field could trigger a collapse of the gap between the lower and upper bands, creating a quantum path for the electrons to go up and down between the bands. 

To make an analogy, Han says, “Imagine some electrons are moving on a second floor. When the floor is tilted by an electric field, electrons not only begin to move but previously forbidden quantum transitions open up and the very stability of the floor abruptly falls apart, making the electrons on different floors flow up and down.

“Then, the question is no longer how the electrons on the bottom floor jump up, but the stability of higher floors under an electric field.”

This idea helps solve some of the discrepancies in the Landau-Zener formula, Han says. It also provides some clarity to the debate over insulator-to-metal transitions caused by electrons themselves or those caused by extreme heat. Han’s simulation suggests the quantum avalanche is not triggered by heat. However, the full insulator-to-metal transition doesn’t happen until the separate temperatures of the electrons and phonons — quantum vibrations of the crystal's atoms — equilibrate. This shows that the mechanisms for electronic and thermal switching are not exclusive, Han says but can arise simultaneously.

“So, we have found a way to understand some corner of this whole resistive switching phenomenon,” Han says. “But I think it's a good starting point.”

Research could improve microelectronics

The study was co-authored by Jonathan Bird, Ph.D., professor and chair of electrical engineering in UB’s School of Engineering and Applied Sciences, who provided experimental context. His team has been studying the electrical properties of emergent nanomaterials that exhibit novel states at low temperatures, which can teach researchers a lot about the complex physics that govern electrical behavior. 

“While our studies are focused on resolving fundamental questions about the physics of new materials, the electrical phenomena that we reveal in these materials could ultimately provide the basis of new microelectronic technologies, such as compact memories for use in data-intensive applications like artificial intelligence,” Bird says.

The research could also be crucial for areas like neuromorphic supercomputing, which tries to emulate the electrical stimulation of the human nervous system. “Our focus, however, is primarily on understanding the fundamental phenomenology,” Bird says.

Other authors include UB physics Ph.D. student Xi Chen; Ishiaka Mansaray, who received a Ph.D. in physics and is now a postdoc at the National Institute of Standards and Technology; and Michael Randle, who received a Ph.D. in electrical engineering and is now a postdoc at the Riken research institute in Japan. Other authors include international researchers representing École Normale Supérieure, French National Centre for Scientific Research (CNRS) in Paris; Pohang University of Science and Technology; and the Center for Theoretical Physics of Complex Systems, Institute for Basic Science.

Since publishing the paper, Han has devised an analytic theory that matches the supercomputer’s calculation well. Still, there’s more for him to investigate, like the exact conditions needed for a quantum avalanche to happen. 

“Somebody, an experimentalist, is going to ask me, ‘Why didn’t I see that before?’” Han says. “Some might have seen it, some might not have. We have a lot of work ahead of us to sort it out."

This study concludes that correlated insulator collapse due to quantum avalanche via in-gap ladder states is a viable mechanism for the emergence of novel quantum states of matter. However, further research is needed to fully understand the implications of this mechanism and its potential applications.