Pines’ ‘Demon’ Particle in Superconductor Offers New Physics Insights

Physicists have stumbled upon an intriguing phenomenon they weren’t even searching for. Known as Pines’ Demon, this effect was spotted in an unusual metal – strontium ruthenate or Sr2RuO4.

The term ‘demon’ might conjure images of the supernatural, but in science, it actually just refers to hypothetical scenarios or thought experiments.

However, Pines’ Demon stands out. It’s not just a concept; it’s a tangible observation, predicted 70 years ago by physicist David Pines.

At its heart, Pines’ Demon is what scientists call a plasmon. To put it simply, plasmons are special energy disturbances in a material, like the ripple on a water surface.

What sets Pines’ Demon apart from typical plasmons is its unique behaviour: it operates without any electrical charge. This happens when electrons, tiny charged particles inside atoms, of varied energy levels go out of sync.

Getting into Strontium Ruthenate’s Mysteries

Plasmons have typically been observed in flat, 2-Dimensional metals. Detecting them, however, is no easy task.

These particles are challenging to detect as they don’t easily interact with light. This is where strontium ruthenate comes in.

This metal behaves predictably, like an efficient energy carrier, at cooler temperatures. But as things heat up, it becomes more mysterious, less predictable.

A study led by Ali Husain shone a light on the quirky nature of strontium, revealing its three distinct electron pathways or ‘bands’.

In looking into this metal’s unique properties, Husain’s team spotted something peculiar. Their data hinted at a new quasiparticle ā€“ think of these as effective stand-ins for real particles in a system.

This particular quasiparticle was unlike any they knew. Upon further investigation, they found some intriguing attributes linked to the demon.

Peter Abbamonte, a physicist from the University of Illinois Urbana-Champaign, shared his excitement, remarking, “Demons have been theoretically conjectured for a long time, but experimentalists never studied them.”

He added, “In fact, we weren’t even looking for it. But it turned out we were doing exactly the right thing, and we found it.”

A New Understanding of Superconductivity

Not only is the presence of Pines’ Demon within strontium ruthenate curious, but it also might have a significant role in how certain materials conduct electricity without resistance ā€“ a phenomenon known as superconductivity.

To achieve superconductivity is a bit like the quest for the Holy Grail in the world of physics, as materials that conduct electricity without any resistance can have numerous practical applications, from efficient power transmission to advanced medical technologies.

Ali Husain, who has since shifted his focus to the quantum tech company, Quantinuum, recalls the unexpected turn their research took:

“At first, we had no idea what it was. Demons are not in the mainstream. The possibility came up early on, and we basically laughed it off. But, as we started ruling things out, we started to suspect that we had really found the demon.”

Given these findings, researchers are eager to dive into other metals, especially those with multiple electron bands, in hopes of understanding more about these so-called demons.

They believe such studies might reveal deeper secrets about the world of superconductivity.