Hexbyte Glen Cove A surprise result for solid state physicists hints at an unusual electron behavior thumbnail

Hexbyte Glen Cove A surprise result for solid state physicists hints at an unusual electron behavior

Hexbyte Glen Cove

An image captured by laser-PEEM showing the arrangement of electrons in a sample of IBSC material. In this technique, images are made from laser light illuminating the sample in two different directions. Linear dichroism (LD) refers to the difference between the images made from these two illumination directions; it allows you to see details you could not see otherwise, such as in this case the distribution of electrons. Credit: Shin et al.

While studying the behavior of electrons in iron-based superconducting materials, researchers at the University of Tokyo observed a strange signal relating to the way electrons are arranged. The signal implies a new arrangement of electrons the researchers call a nematicity wave, and they hope to collaborate with theoretical physicists to better understand it. The nematicity wave could help researchers understand the way electrons interact with each other in superconductors.

A long-standing dream of solid state physicists is to fully understand the phenomenon of superconductivity—essentially electronic conduction without the resistance that creates heat and drains power. It would usher in a whole new world of incredibly efficient or powerful devices and is already being used on Japan’s experimental magnetic levitation bullet train. But there is much to explore in this complex topic, and it often surprises researchers with unexpected results and observations.

Professor Shik Shin from the Institute for Solid State Physics at the University of Tokyo and his team study the way electrons behave in iron-based superconducting materials, or IBSCs. These materials show a lot of promise as they could work at higher temperatures than some other which is an important concern. They also use less exotic material components so can be easier and cheaper to work with. To activate a sample’s superconducting ability, the material needs to be cooled down to several hundreds of degrees below zero. And interesting things happen during this cooling process.

A diagram of the experimental setup pioneered by the team. Credit: Shin et al.

“As IBSCs cool down to a certain level, they express a state we call electronic nematicity,” said Shin. “This is where the crystal lattice of the material and the electrons within it appear to be arranged differently depending on the angle you look at them, otherwise known as anisotropy. We expect the way electrons are arranged to be tightly coupled to the way the surrounding crystal lattice is arranged. But our recent observation shows something very different and actually quite surprising.”

Shin and his team used a special technique developed by their group called laser-PEEM (photoemission electron microscopy) to visualize their IBSC sample on the microscopic scale. They expected to see a familiar pattern that repeats every few nanometers (billionths of a meter). And sure enough the crystal lattice did show this pattern. But to their surprise, the team found that the pattern of electrons was repeating every few hundred nanometers instead.

This disparity between the electron nematicity wave and the crystalline structure of the IBSC was unexpected, so its implications are still under investigation. But the result could open the door to theoretical and experimental explorations into something fundamental to the phenomenon of superconductivity, and that is the way that electrons form pairs at low temperatures. Knowledge of this process could be crucial to the development of high-temperature superconductivity. So if nematicity waves are related, it is important to know how.

“Next, I hope we can work with to further our understanding of waves,” said Shin. “We also wish to use laser-PEEM to study other related materials such as metal oxides like copper oxide. It may not always be obvious where the applications lie, but working on problems of fundamental physics really fascinates me.”

The study is published in the journal Science.

More information:
T. Shimojima et al, Discovery of mesoscopic nematicity wave in iron-based superconductors, Science (2021). DOI: 10.1126/science.abd6701

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Hexbyte Glen Cove How rail accidents with hazardous materials affect people's property values thumbnail

Hexbyte Glen Cove How rail accidents with hazardous materials affect people’s property values

Hexbyte Glen Cove

Credit: Pixabay/CC0 Public Domain

A decade ago, U.S. crude oil was not transported by rail in the United States—not one drop. After an unprecedented expansion of domestic energy production, the use of trains became more common.

When these hazardous petrochemical materials pass through with dense populations, the public has good reason to be concerned. But, whether it’s by train, boat or , transportation only becomes a mainstream topic when there’s an accident, which can cause human health risks, property damage, evacuation and environmental degradation.

These leave behind obvious physical damages. But what about the impact on people’s property values?

The University of Delaware’s Martin Heintzelman and his collaborators published a new research study in the Journal of Urban Economics on derailments involving and the impact on property values. They found the negative impact on housing property values lingers for almost a year and a half. The project was motivated by the dramatic increase in shipment of oil by rail in the last decade and prominent accidents like the July 2013 Lac-Megantic disaster in Quebec. In one of the worst rail disasters in Canadian history, 47 people were killed and more than 40 buildings razed. A common theme at the center of the tragedy was a small town grappling with the aftermath. Similar high-profile accidents in the U.S. increased attention on freight rail safety and the aging fleet of tanker cars.

The central debate of hazardous material transportation is the comparison between rail and pipeline.

“There has been substantial debate about the expansion of petroleum pipeline networks. This combination of issues got me thinking about the tradeoffs associated with these infrastructure decisions,” said Heintzelman, the Department of Applied Economics and Statistics chair and professor. “One piece of that is to understand how homeowners value risks they may face from rail accidents where more hazardous chemicals are being shipped via rail.”

The researchers specifically wanted to know the effect of derailments on property values. They looked at 33 derailments in the state of New York between 2004 and 2013. On average, a derailment depreciated housing values within a one-mile radius by 5% to 8%. It took 480 days for housing prices of affected properties to return to pre-accident levels. Findings also showed that the impacts of derailments on property values were limited to the local area. People who lived farther away were spared, with no significant impact. At other locations unrelated to the accident, media coverage had no effect on property values with houses nestled near rail lines.

“This suggests that people living in the market only respond to local accidents and not to general concerns about being near rail lines,” said Heintzelman. “It was somewhat surprising to find that major accidents did not have a significant broader impact, since we expected these accidents to impact people’s risk perceptions of rail lines.”

In 2010, U.S. was not transported by rail. By 2014, rail shipments peaked at 25.8% of all oil transport. The most recent annual figures (2019) broke down to 87.9% shipped by pipeline, 7.4% by rail and 4.7% by water.

“The shift to rail was driven by the huge expansion in domestic oil production since 2007 and an existing pipeline network not equipped to deal with that change,” said Heintzelman. “Since 2014, pipeline capacity has expanded and caught up to demand.”

Compared to rail, sending oil via pipeline is a much safer endeavor. But expanding this network requires new infrastructure in sometimes remote and ecologically sensitive areas. Heintzelman points out that expanding rail transport takes advantage of existing infrastructure in areas already subject to many of the negative externalities associated with rail freight.

“Additional rail transport, in general, does not require additional approvals, while pipelines do require that,” said Heintzelman. “This made pipelines a focus for climate change activism as they are seen as additional investment in an industry not compatible with climate goals, and potentially stopped by the permitting process.”

Of the many studies that have investigated how disasters affect , most suggest that people react in the immediate aftermath, but property prices typically recover soon after as the public’s reaction to the accident fades with time.

“It is surprising that big events do not seem to drive the sort of general re-evaluation of risk that you might expect,” said Heintzelman. “The only people who seem to respond are those directly affected and very near an accident.”

With the study published, Heintzelman plans to extend his related research on the value of environmental amenities and the impacts, values, and drivers of renewable and other energy infrastructure.

More information:
Chuan Tang et al. Rail accidents and property values in the era of unconventional energy production, Journal of Urban Economics (2020). DOI: 10.1016/j.jue.2020.103295


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