Tag Archives: Science & Technology

Superconductivity Gets A New Spin From University of Marlyand Physics Department

When you plug in an appliance or flip on a light switch, electricity seems to flow instantly through wires in the wall. But in fact, the electricity is carried by tiny particles called electrons that slowly drift through the wires. On their journey, electrons occasionally bump into the material’s atoms, giving up some energy with every collision.

The degree to which electrons travel unhindered determines how well a material can conduct electricity. Environmental changes can enhance conductivity, in some cases drastically. For example, when certain materials are cooled to frigid temperatures, electrons team up so they can flow uninhibited, without losing any energy at all – a phenomenon called superconductivity.

Now a team of researchers from the University of Maryland (UMD) Department of Physics, together with collaborators, has seen exotic superconductivity that relies on highly unusual electron interactions. While predicted to occur in other non-material systems, this type of behavior has remained elusive. The team’s research, published in the April 6 issue of Science Advances, reveals effects that are profoundly different from anything that has been seen before with superconductivity.

Electron interactions in superconductors are dictated by a quantum property called spin. In an ordinary superconductor, electrons, which carry a spin of 0.5, pair up and flow uninhibited with the help of vibrations in the atomic structure.

This theory is well-tested and can describe the behavior of most superconductors. In this new research, the team uncovers evidence for a new type of superconductivity in the material YPtBi, one that seems to arise from spin-3/2 particles.

“No one had really thought that this was possible in solid materials,” explains Johnpierre Paglione, a UMD physics professor and senior author on the study. “High-spin states in individual atoms are possible but once you put the atoms together in a solid, these states usually break apart and you end up with spin one-half. ”

Finding that YPtBi was a superconductor surprised the researchers in the first place. Most superconductors start out as reasonably good conductors, with a lot of mobile electrons – an ingredient that YPtBi is lacking. According to the conventional theory, YPtBi would need about a thousand times more mobile electrons in order to become superconducting at temperatures below 0.8 Kelvin. And yet, upon cooling the material to this temperature, the team saw superconductivity happen anyway. This was a first sign that something exotic was going on inside this material.

After discovering the anomalous superconducting transition, researchers made measurements that gave them insight into the underlying electron pairing. They studied a telling feature of superconductors – their interaction with magnetic fields.

As the material undergoes the transition to a superconductor, it will try to expel any added magnetic field from its interior. But the expulsion is not completely perfect. Near the surface, the magnetic field can still enter the material but then quickly decays away. How far it goes in depends on the nature of the electron pairing, and changes as the material is cooled down further and further.

To probe this effect, the researchers varied the temperature in a small sample of the material while exposing it to a magnetic field more than ten times weaker than the Earth’s. A copper coil surrounding the sample detected changes to the superconductor’s magnetic properties and allowed the team to sensitively measure tiny variations in how deep the magnetic field reached inside the superconductor.

The measurement revealed an unusual magnetic intrusion. As the material warmed from absolute zero, the field penetration depth for YPtBi increased linearly instead of exponentially as it would for a conventional superconductor.

This effect, combined with other measurements and theory calculations, constrained the possible ways that electrons could pair up. The researchers concluded that the best explanation for the superconductivity was electrons disguised as particles with a higher spin – a possibility that hadn’t even been considered before in the framework of conventional superconductivity.

The discovery of this high-spin superconductor has given a new direction for this research field. “We used to be confined to pairing with spin one-half particles,” says Hyunsoo Kim, lead author and a UMD assistant research scientist. “But if we start considering higher spin, then the landscape of this superconducting research expands and just gets more interesting.”

For now, many open questions remain, including how such pairing could occur in the first place. “When you have this high-spin pairing, what’s the glue that holds these pairs together?” says Paglione. “There are some ideas of what might be happening, but fundamental questions remain-which makes it even more fascinating.”

SpaceX Launches Cargo to Space Station Using Recycled Rocket & Spaceship

SpaceX blasted off a load of supplies Monday for the International Space Station aboard a rocket and a cargo ship that have both flown before, marking the second such flight for the California-based company.

“Falcon 9 is on its way,” a SpaceX commentator said as the white rocket surged skyward over Cape Canaveral, Florida at 4:30 pm (2030 GMT).

SpaceX’s Jessica Jensen, director of Dragon mission management, said the booster had previously launched in August 2017, and the Dragon flew to the space station in April 2016.

SpaceX’s first such double-recycle resupply mission for NASA flew to the orbiting outpost in December 2017.

The effort is part of SpaceX’s mission to lower the cost of space flight by re-using costly, multimillion-dollar components that typically have been discarded into the ocean after each launch.

“What is really neat about this is it is becoming the norm,” Jensen said.

Monday’s trip marked SpaceX’s 14th resupply mission for NASA under a $1.6 billion contract that aims to guarantee much-needed supplies and equipment to the astronauts living in orbit.

The capsule is packed with about 5,800 pounds (2,600 kilograms) of food and science experiments, including one to study thunderstorms and another to test drug development in space.

The cargo ship is scheduled to latch onto the space station early Wednesday, and will stay in orbit for about a month before returning to Earth.

NASA Learns to Predict Mudslide Threats In Real-Time

For the first time, scientists can look at landslide threats anywhere around the world in near real-time, thanks to satellite data and a new model developed by NASA.

The model, developed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland estimates potential landslide activity triggered by rainfall. Rainfall is the most widespread trigger of landslides around the world. If conditions beneath Earth’s surface are already unstable, heavy rains act as the last straw that causes mud, rocks or debris – or all combined – to move rapidly down mountains and hillsides.

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The model is designed to provide a more indepth understanding of where and when landslide hazards are present and improve estimates of long-term patterns. A global analysis of landslides over the past 15 years using the new open source Landslide Hazard Assessment for Situational Awareness model was published in a study released online on March 22 in the journal Earth’s Future.

“Landslides can cause widespread destruction and fatalities, but we really don’t have a complete sense of where and when landslides may be happening to inform disaster response and mitigation,” said Dalia Kirschbaum, a landslide expert at Goddard and co-author of the study. “This model helps pinpoint the time, location and severity of potential landslide hazards in near real-time all over the globe. Nothing has been done like this before.”

The model estimates potential landslide activity by first identifying areas with heavy, persistent and recent precipitation. Rainfall estimates are provided by a multi-satellite product developed by NASA using the NASA and Japan Aerospace Exploration Agency’s Global Precipitation Measurement (GPM) mission, which provides precipitation estimates around the world every 30 minutes. The model considers when GPM data exceeds a critical rainfall threshold looking back at the last seven days.

In places where precipitation is unusually high, the model then uses a susceptibility map to determine if the area is prone to landslides. This global susceptibility map is developed using five features that play an important role in landslide activity: if roads have been built nearby, if trees have been removed or burned, if a major tectonic fault is nearby, if the local bedrock is weak and if the hillsides are steep.

If the susceptibility map shows the area with heavy rainfall is vulnerable, the model produces a “nowcast” identifying the area as having a high or moderate likelihood of landslide activity. The model produces new nowcasts every 30 minutes.

The study shows long-term trends when the model’s output was compared to landslide databases dating back to 2007. The team’s analysis showed a global “landslide season” with a peak in the number of landslides in July and August, most likely associated with the Asian monsoon and tropical cyclone seasons in the Atlantic and Pacific oceans.

“The model has been able to help us understand immediate potential landslide hazards in a matter of minutes,” said Thomas Stanley, landslide expert with the Universities Space Research Association at Goddard and co-author of the study.

“It also can be used to retroactively look at how potential landslide activity varies on the global scale seasonally, annually or even on decadal scales in a way that hasn’t been possible before.”