Room-temperature superconductors have the potential to convert everything from power grids to particles
As an accelerator to computers, researchers are still trying to understand how these materials work at the atomic level.
Recently, Lex Kemper, a physicist at North Carolina State University, Chemistry About the unique properties of a material called yttrium barium copper oxide, or YBCO.
The team discovered that YBCO’s superconductivity is in an unexpected way intertwined with another phenomenon known as charge density waves (CDWs) or ripples in electron density in materials. These CDWs become stronger when YBCO superconductivity is turned off. But they were surprised that CDWs were also suddenly more spatially organized. This suggests that superconductivity fundamentally shapes the shape of CDWs on a nanoscale.
So what does this mean? The abstract asked Kemper to share his insights.
TA: The search for room-temperature superconductors has the potential to transform many industries. In this paper, we have looked at the relationship between superconductivity and charge density waves in a material called YBCO. Let’s start with a few basic definitions – what gives a material superconductivity?
Kemper: This is a really good question. From BCS theory, it is known that superconductivity can occur because two electrons can interact indirectly through a kind of force, lattice vibration. They form a bound pair called a Cooper pair, and when all the related electrons in the material do it, they are in a state called superconductivity. Currently, this theory cannot be applied directly to YBCO. This has spurred decades of research into what is happening with these materials. Currently, we believe that the coupling force is caused by the magnetic fluctuation of the material, not by the lattice vibration.
TA: What is a charge density wave?
Kemper: Imagine you have a row of people all evenly spaced-that’s your first structure. Next, pair each set of two people and bring them a little closer. This is the easiest way to see the charge density wave. In essence, it’s an additional pattern on top of what already existed. YBCO believes that this additional patterning occurs because the electrons are acting alone, not because the atoms are involved.
TA: I noticed that the charge density waves were stronger and more organized when the YBCO superconductivity was turned “off” using a laser pulse. That is, superconductivity and charge density waves are somehow connected on a nanoscale. What does this mean?
Kemper: This study has shown no way to find or create high-temperature superconductors. Rather, it is a step towards understanding the actual basic physics. It was found that when superconductivity was suppressed, the charge density waves maintained their pattern on a much longer scale. This shows that they are competing, but it’s a nanoscale structured method. This sheds new light on the coexistence / intertwined order issues found in these materials.
TA: Why is this intertwined order considered a “problem”, or something we need to study further? Can’t understand why / how it happens? Does it interfere with our ability to utilize certain properties of the material?
Kemper: In short, we don’t really understand why this material is superconducting and why it exhibits charge density waves, not to mention the combination of the two! A good way to understand something in physics is to get in the way a bit and see how it reacts (this is how almost every experiment works, and much more. How the properties of the material occur). In this case, we perturbed with an ultrafast laser pulse and observed the resulting dynamics. This revealed something new that I had never known before. In this case, it revealed the existence of a kind of nanoscale patterning and excluded some other patterning options (whether nanoscale or not).
TA: What is the next step in this task?
Kemper: The next step is to refine our experiments and theories and come up with new ways to look at this problem. More broadly, we hope that this field will incorporate this work into the idea of the basic physics of charge density waves and superconductivity in these materials.
TA: Do you think you will reach a usable room-temperature superconductor in the near future?
Kemper: This is a really good question. i hope so. What I’m hoping for is that if that happens, it comes from an unexpected corner of the vast ocean that we may not have explored yet.