Preet Bharara:
From CAFE and the Vox Media Podcast Network, this is Stay Tuned In Brief. I’m Preet Bharara.
In recent weeks, there’s been a lot of buzz about something called a room temperature superconductor. The surge in interest comes after researchers in South Korea published a paper on a material named LK-99, proclaiming it the first room temperature superconductor. Such material which could conduct electricity with unmatched deficiency under everyday conditions would be groundbreaking, but LK-99 may not be the game changer many anticipated. Still, the media attention has highlighted the potential significance of a room temperature superconductor for science and society. How does it work? What could change if we discover one, and just how close are we?
Joining me to dig into this is Dr. Richard Greene. He’s a professor of physics at the University of Maryland and was the founding director of its Center for Superconductivity Research. He’s been studying superconducting and other innovative materials for over 50 years.
Professor, welcome to the show.
Dr. Richard Greene:
Thanks very much. It’s a pleasure to be here.
Preet Bharara:
So I’m excited to talk to you about this for many reasons. But first, for folks who are not steeped, let’s do a couple of basic questions.
Dr. Richard Greene:
Absolutely.
Preet Bharara:
What is a conductor? What is a superconductor and what are the challenges to superconducting?
Dr. Richard Greene:
Well, a conductor, I think most of us are familiar with conductors, like pieces of metal, like a copper wire conduct electricity. What is electricity? Electricity are charged particles which we now know are electrons. So when you push electrons through a piece of copper or any other metal for that matter, you get a current, and this is charged conduction.
However, it isn’t perfectly conducting because the electrons when they’re moving through the wire bump into the atoms that are there, or they might bump into the sidewalls of the wire as well. But mostly they bump into the atoms that are there in the copper wire, which aren’t moving. The electrons are freed from the copper atoms, and then they just flow like water through the metal. But they bump into the atoms, and the atoms are vibrating around at normal temperatures, and so they lose some energy. So it’s like rolling a ball down a hill where there’s a bunch of rocks there. The ball will lose some energy and will eventually, of course, come to a stop. But you have to carry the ball back up to the top of the hill and make it go again.
Well, we have something like a battery or a generator that keeps pushing the electrons through the wire. So they keep going through the wire, but they bang into things so they lose some energy. And so the wire heats up. An example of a hot wire might be your toaster. I’m sure you’ve probably looked inside your toaster and you see some wires in there that are glowing hot. Well, that’s because those wires have a lot of electrical resistance. The electrons bang into the atoms there more frequently than they do in copper, and so it heats up more. In fact, all metals have electrical resistance, and so some energy is lost in them.
Preet Bharara:
So then a superconductor is what?
Dr. Richard Greene:
Now a superconductor is, well you might say it’s like superman compared to man, there are some extra things that happen. And the electrical current, the electrons flow through the wire, but they don’t lose any energy. Because there’s something magical about a superconductor. And how does it work? Well, we’ll get into that later. But the electrons are bound together in pairs in a superconductor. You now have pairs of electron that are bound together. And when they bump into the atoms, it’s not enough energy to break apart these pairs of electrons. The current is being carried by pairs of charged particles, two of them.
So in a sense, you know that something like water is held together by forces, and H2O is water. It takes energy to break apart the thing that’s holding the water together. And the same is true here. When you form into the superconducting state, there’s something that binds these electrons together, and the banging into the atoms is not enough to break them apart. So the current just flows with no resistance.
Preet Bharara:
So a conductor in the form of copper we use all the time, we use them in our appliances and they carry electricity, we don’t use superconductors. And you’re going to explain the reason why that is.
Dr. Richard Greene:
Well, let’s go back a bit and say, when superconductors were discovered, they were only really discovered a little over a 100 years ago when people learned how to cool down metals, and there are ways of cooling things down. There is an absolute zero of temperature where all motion stops in principle. And people learned how to liquefy gases like hydrogen and helium, and then that would lower the temperature down, getting close to this absolute zero. And people wanted to know, “Well, what happens to metals when you cool them down where supposedly all motion stops?”
Well, there were a lot of theories about that. The electrons might stop moving, so the material would become insulating. Or the electrical conductivity would eventually get very, very high, but nobody knew.
But then this experiment was done. As they were cooling it down, and suddenly at four degrees above absolute zero, the electrical resistance went completely to zero. Now nobody expected this, and nobody had a theory for this. And this was the first superconductor. Of course, the Nobel Prize was awarded to the person who discovered this. Over the years more and more… And that was an element that was, I think mercury or tin. So many of the elements that we’re familiar with, are superconductors when you cool them down to low temperature.
Preet Bharara:
Right. Which is not a condition that’s easily replicable in someone’s home.
Dr. Richard Greene:
Exactly, exactly.
Preet Bharara:
So the superconductors offer this great efficiency. We’ll discuss the possibilities there, but they’re impractical for wide use. Hence, the excitement about what we call a room temperature superconductor. Why so much excitement about that?
Dr. Richard Greene:
The excitement there is because if you have such a superconductor room temperature, you don’t need to cool things down. You don’t need all the equipment that you need to cool something down. And that takes a lot of effort. I mean, we do have superconductors now that work, and they’re used primarily to create magnetic fields by turning them into coils of wire.
Preet Bharara:
Like MRIs.
Dr. Richard Greene:
Like MRI has a superconducting magnet in it. And the particle physicists use superconducting magnets at CERN when they’re smashing their particles together.
Preet Bharara:
MRI machines are very expensive.
Dr. Richard Greene:
Yes, they’re expensive.
Preet Bharara:
And in part because of the necessity to cool.
Dr. Richard Greene:
Yes, in part because you have to cool down the magnets to get the fields, the nice high magnetic fields that you need to do MRI.
Preet Bharara:
For people who have forgotten from high school science what absolute zero is, and hence don’t know what four degrees above absolute zero would be. Could you remind us?
Dr. Richard Greene:
This is a scale called the Kelvin scale. So absolute zero is zero on the Kelvin scale. Room temperature would be something like 300 degrees on this Kelvin scale.
Preet Bharara:
But if you convert to Fahrenheit, my recollection is, and we’re going to edit this out if I’m wrong. From high school, is that absolute zero is minus 273 Fahrenheit. Am I wrong?
Dr. Richard Greene:
It’s minus 273 Celsius.
Preet Bharara:
Oh, Celsius. Okay.
Dr. Richard Greene:
Yeah. Celsius.
Preet Bharara:
So it’s half right.
Dr. Richard Greene:
Well, to tell you the truth, I never know when anything is in Celsius or Fahrenheit.
Preet Bharara:
It’s Kelvin for you.
Dr. Richard Greene:
It’s just not the way we think. But at any rate, the present day superconductors are not working at temperatures that are useful. You can use them for some very specialized things, but you’re not going to cool your wires down in your house. You’re not going to try to transmit electricity across the country by cooling down a superconducting wire.
Preet Bharara:
So what happened in South Korea that caused all this buzz?
Dr. Richard Greene:
I don’t know what those guys were drinking actually.
Preet Bharara:
So you’re saying it ain’t true.
Dr. Richard Greene:
Okay. Yes, it ain’t true. It ain’t true, but…
Preet Bharara:
Well, can I ask, how does that happen? I don’t mean to disparage anyone. Were they perpetrating a fraud? Did they just get it wrong?
Dr. Richard Greene:
No, they were not perpetrating a fraud. I’m almost sure they were not. I think they just were inexperienced in how to do certain types of measurements. They did measurements, and we can talk about this, that made it look like the material was superconducting. But in fact, it could be explained by other reasons. And now people have done more experiments and there are enough experiments now that show that it really is not a superconducting material. They made some mistakes in their work, but this is not uncommon.
There are claims made about things and it looked interesting at the top of it. The first glance you would say, “Oh my gosh, these guys have a superconductor.” And then you look a little more carefully and you realize, “Well, maybe they didn’t do this measurement exactly right, or they didn’t do this other measurement exactly right.” And then more people, of course, are going to check something like this out. It’s an extraordinary claim, and if you have an extraordinary claim, you better have some extraordinary evidence for it. It’s pretty quick, I must say. Within three weeks, there are now enough other groups that have done this that we realize this is not a room temperature superconductor. But we’ll get back and talk about the possibilities of one.
Preet Bharara:
First, I want to talk about that of course. But just so people have a sense of how groundbreaking a thing it would be. That’s why a lot of people are talking about it. There’s an Oxford professor of materials who said, “A technologically viable room temperature superconductor isn’t just Nobel Prize territory. If you patented it, it’s of incalculable value essentially.” It’s transformational on so many things, he also said.
Could you just give a picture of how life would be different, technology would be different, our daily lives, if tomorrow there was a room temperature superconductor that was readily available as a material?
Dr. Richard Greene:
I’m not sure I would go quite as far as this Oxford professor, but I think it would have certainly some very important impacts.
Well first of all, you could replace all the electrical wiring that we have now and use a superconducting wire. If you transmit electricity from one part of the country to the other, which is something we might want to do nowadays, where we have solar generation of electricity and we have wind farms often far away places, and we want to transmit that electricity to our cities where it’s mostly used, there’s a loss of energy there. People at, well maybe 10%, you see various estimates, 5%, 15%. This is not going to solve the climate crisis. But it would increase the efficiency of our ability to transmit energy all around. I think it would put copper companies out of business, that’s for sure.
Motors and generators would become more efficient. Probably some of our wind farms would become more efficient because they use motors in there.
Also, the storage of energy might become more efficient. Right now they’re talking about using batteries to store the energy from wind farms, or solar places because that’s an intermittent source of energy. You want to generate the energy when the wind’s blowing, but then you might not be using it at that time and you want to store it somewhere. So the idea now is to store it in batteries, but you could store it in a superconducting current wire going around in a circle. You basically could store it in the magnetic energy that’s associated with a superconductor. So that might be a use.
Certainly probably would end up in electronics because very fast switches can be made out of superconductors. I don’t think you would be replacing silicon technology in your computers, but there might be some places where superconducting switches might be quite useful.
I don’t think it would be showing up in your iPhone, but it might be. Because I think you know that your phone sometimes heats up when you’re charging it and when you’re using it. It’s losing some of its energy because there are connections in there. There are copper connection wires. And every time there’s a connection, there’s some heat lost in the resistance of those wires. So if you put superconductors in there, you would not be losing heat there. So certainly your laptop, for example. I’m sitting here in front of my laptop and it’s getting pretty hot. Some of that heating would go away if I had superconducting interconnects if you want.
Preet Bharara:
What about public transit? Are we going to have levitating trains?
Dr. Richard Greene:
Public transit? Okay. Well, okay. Why did people get so excited about this LK-99? I think one of the reasons they got excited is one of the pictures from this paper was showing the material levitating over a magnet. Now that’s another property of superconductors that basically they expel all magnetic fields that go through them, and they basically act like an opposite bar magnet.
Imagine you have a magnet with a north-south pole, with the north pole facing up, and then you have a superconductor sitting on top of it. When the material goes superconducting, all the magnetic field from the magnet gets expelled out. And then the superconductor acts as if it’s another magnet with the north pole facing the north pole of the original magnet. And you know if you bring two north poles together, what do they do? They repel, two north poles of a magnet.
So that’s something that people get excited about, “Wow, I’m going to be able to levitate trains.” Well, you probably can levitate trains that way. It’s going to be damn expensive to do it, but I think it will be possible.
There’s another thing I should say here. Suppose we discover a room temperature superconductor, and I think we will actually. LK-99 may not be it, but I think we’re going to find one. But will it be a wire that we can use as easily as copper? Copper is a very ductile wire. We can bend it into all sorts of shapes. It’s very useful because of that point of view. If we discover a room temperature superconductor it most likely won’t have such nice other properties. So there’ll be a period of development there. It will take a while to do all these things.
Preet Bharara:
When we say, this is a dumb question perhaps, but these materials that are being tested for superconductivity, are they all just naturally occurring in nature like the metals you mentioned, or are we making them?
Dr. Richard Greene:
No, that’s a very good question, actually. A lot of the superconductors are compounds that we have synthesized, that we make. They’re not just the elements. We don’t use the elements. So for example, the one I think that’s used in MRI magnets is niobium-titanium that they use. It’s an alloy that’s used in some magnets. But then there’s niobium-3-tin, which is also used.
About 30 years ago, a very exciting bunch of superconductors was discovered because they worked above the boiling point of liquid nitrogen, which is 77 degrees kelvin. I don’t know what it is in, you know. It’s well below room temperature.
Preet Bharara:
Yes.
Dr. Richard Greene:
But I think a lot of people have seen liquid nitrogen and it’s much easier to produce, and it’s easier to use. Those superconductors, they were copper oxide superconductors, they were materials. I’ll give you the formula of one of them, yttrium, barium 2, copper 3, oxygen 7.
Now, nobody in their right mind would pick that random collection of elements out and try to make a compound out of it. There was a little bit of serendipity in discovering these copper oxide superconductors. And once they were discovered, and it was proven in this case correct that they did indeed super conduct above liquid nitrogen around 90 degrees kelvin actually, then a lot of development went in to finding more of them like this. And there was a lot of hope that we would eventually find a room temperature superconductor that was made from these copper oxides or something like these copper oxides.
So yeah, in general, there’s a lot of combinations of materials you can make, and almost every practical superconductor is a manmade thing. You don’t find it in nature.
Preet Bharara:
Can we just ask AI to find us a superconductor that works at room temperature?
Dr. Richard Greene:
No, that’s another really good question. And yes, and people are trying to do that. The name I’ve heard is called machine learning, but basically it’s AI. You take as many properties as you know of a certain bunch of elements and you say, “Well, if I combine them this way, I put them in this kind of a structure.” And by the way, the structure of your material is very important. And what I mean by structure is where are the atoms located in a material? So it’s called the crystal structure. It’s one of the basic things that condensed metaphysicists like myself or material scientists need to look at. If you make some new material, you want to know where are the atoms. That’s extremely important for then predicting what their properties will be.
So that’s what AI can do. They could speed up this kind of process. They might be able to say, “Okay, if you combine these three elements together in this proportion, they might form this crystal structure. And if they form this crystal structure, it’ll be a room temperature superconductor.” So that might happen.
Preet Bharara:
So I’m going to ask you finally to make a prediction, which most people who come on the show don’t like to do, whether it’s politics or science. When are we going to have one, game changing room temperature superconductor?
Dr. Richard Greene:
Okay. Again, you know what predictions are worth, right?
Preet Bharara:
I do. Because the show is free, so you get what you pay for.
Dr. Richard Greene:
I can very confidently tell you that we’re going to have one in 30 years.
Preet Bharara:
Okay, that’s pretty good.
Dr. Richard Greene:
I think the odds are good and I’ll tell you why. There have been some credible superconductors that work very close to room temperature. They are compounds that contain hydrogen in them. They’re called hydrides. And they work I’d say within 10 or 20 degrees of room temperature. In fact, there’s a guy from Siberia who says he already has a room temperature superconductor. Where he lives, it’s working at room temperature.
Preet Bharara:
Right.
Dr. Richard Greene:
But these things are real. We understand how they work. The only problem is you need tremendous pressure to make them. You need something like two million times the earth’s atmosphere to prepare these materials, and they’re superconducting then under those very high pressures.
Preet Bharara:
Well, that’s not practical either.
Dr. Richard Greene:
That’s not practical at all. But maybe we’re going to figure out how to stabilize such a material at atmospheric pressure. I have a feeling that that may be a good approach for people to take. I actually am fairly optimistic that we will have a room temperature superconductor within 30 years. But again, it will take after that some time to make it into something practical and useful.
Preet Bharara:
Well, as I always say here, when we don’t know what the future will hold, stay tuned.
Dr. Richard Greene:
Very good.
Preet Bharara:
Professor Richard Greene, thanks so much for being with us and educating us.
Dr. Richard Greene:
Thanks a lot.
Preet Bharara:
For more analysis of legal and political issues making the headlines, become a member of the CAFE Insider. Members get access to exclusive content, including the weekly podcast I host with former US Attorney, Joyce Vance. Head to cafe.com/insider to sign up for a trial. That’s cafe.com/insider.
If you like what we do, rate and review the show on Apple Podcasts or wherever you listen. Every positive review helps new listeners find the show.
Send me your questions about news, politics, and justice. Tweet them to me at Preet Bharara with the hashtag #AskPreet. You can also now reach me on Threads, or you can call and leave me a message at 669-247-7338. That’s 669-24-PREET. Or you can send an email to letters@cafe.com.
Stay Tuned is presented by CAFE and the Vox Media Podcast Network. The executive producer is Tamara Sepper. The technical director is David Tatasciore. The senior producer is Adam Waller. The editorial producer is Noa Azulai, and the CAFE team is Matthew Billy, David Kurlander, Jake Kaplan, Nat Weiner, Namita Shah, and Claudia Hernández. Our music is by Andrew Dost. I’m your host, Preet Bharara. Stay tuned.
