Turning Hydrogen Into A Metal Could Lead To New Superconductors
Six decades ago, a group of physicists came up with a theory that described electrons at a low temperature that could attract a second electron. If the electrons were in the right configuration, they could conduct electricity with zero resistance. The Bardeen-Cooper-Schrieffer theory, named after the three physicists, is the basis for how superconductivity works at a quantum level. Superconductivity would allow electricity to flow with no loss of heat from its system.
Since that time, scientists have been trying to find a real-world material that fits that theory. One way to achieve this is by turning hydrogen into a metal. This is accomplished by squeezing hydrogen gas between two diamonds at such a high pressure that it solidifies. That metal then becomes a superconductor at room temperature. Previously, achieving zero resistance had only been possible by cooling the superconductor to near absolute zero.
In this segment, Ira and Gizmodo science writer Ryan Mandelbaum talk with physicist Maddury Somayazulu and theoretical chemist Eva Zurek about the progress towards creating a room-temperature superconductor and how this type of material could be used in quantum computing and other technology.
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Ryan Mandelbaum is a science writer at Gizmodo in New York, New York.
Maddury Somayazulu is the Group Leader of the X-ray Science Division at Argonne National Laboratory in Lemont, Illinois.
Eva Zurek is a professor of Chemistry at the University at Buffalo in Buffalo, New York.
IRA FLATOW: This is Science Friday. I’m Ira Flatow. You know, all of our electronics works by conducting a charge and passing it along. Almost every material can carry a charge, even wood, metal, glass. But some of our materials are better. They’re better conductors than others in shuttling those electrons around.
Well, what if there was a material that could perfectly carry a charge? No resistance. No loss of heat. Everything stays in that system. And what if you could get it to work at room temperature?
That’s a very hard thing to accomplish. And scientists out there are trying to create this type of superconductor. And they’re using a material that you might not think of, hydrogen, the most abundant known gas in the universe. Scientists are trying to turn that free-floating gas into a metal, and then into a superconductor.
How do you do that? That’s the topic of a story that my next guest reported on. And he is here to talk about it. Ryan Mandelbaum, a science writer for Gizmodo, here in our studios.
RYAN MANDELBAUM: Hey, Ira. How’s everything going?
IRA FLATOW: It’s great. You know, this is like the holy grail sort of.
RYAN MANDELBAUM: Yeah. I mean, it’s amazing. If it could exist, it could be revolutionary.
IRA FLATOW: OK. Let’s talk about– backup a little bit and talk about the theory that predicted superconductivity. What does it say? How does it work?
RYAN MANDELBAUM: Sure. So superconductivity is interesting because it was over 100 years ago where scientists found that liquid mercury at very cold temperatures could carry charge without resistance, which basically, that just means that the wire doesn’t heat up when you pass electric charge to it. It’s resistanceless. And this would be big for transferring energy.
Now, that was at really really, really cold temperatures. I mean, we’re talking negative 452 degrees Fahrenheit, just a few degrees above absolute zero, which you all might know is the temperature at which matter has no heat. So it’s hard to do this.
But since then, theorists finally developed a theory to understand and explain what was going on. And this has now driven research into finding superconductors at higher temperatures, where the ideal superconductor would be one at room temperature so you could operate it in a room.
IRA FLATOW: But theoretically, is it possible to create a superconductor at– it’s so cold now. And we have them powering MRI machines and the Large Hadron Collider. Theoretically, it’s possible then to create one, maybe, at room temperature.
RYAN MANDELBAUM: Yeah. I mean, the hope is that– theoretically, I think that– I haven’t seen the most recent theories. But they get close. I mean, right now, even experimentally actually, they’ve been able to create tiny amounts of superconducting material at it seems almost the temperature in Chicago on a cold day.
IRA FLATOW: [LAUGHTER] OK. We’ll talk about that a little bit more after we talk a little bit about the experiments with hydrogen. You wrote about hydrogen. It doesn’t sound like the easiest thing to work with. How do you turn hydrogen into a metal and then a superconductor?
RYAN MANDELBAUM: Well, you might remember from high school chemistry that matter is sensitive to both temperature and pressure. So if you compress things enough, they might become a liquid or a solid. So hydrogen, it’s theorized, under high enough pressure would become a metal and would potentially be a superconducting metal. And so just sort of both for curiosity’s sake and for hoping to find this superconductor, scientists have begun these high-pressure experiments hunting for metallic hydrogen.
IRA FLATOW: Yeah. And you visited one of these labs.
RYAN MANDELBAUM: I did. I was actually at the Carnegie Institute in Washington. And I watched– I wasn’t able to watch sort of the creation of
This, but I watched– I saw all of the equipment used to actually compress hydrogen gas. And you can’t– nobody’s actually– we don’t know. But it seems that nobody’s created metallic hydrogen yet. But by adding a new element like certain– like lanthanum, for example, you can sort of dope it in a way that it takes on some of these higher-temperature superconductive properties.
IRA FLATOW: And then to create it, they squeeze it between two diamonds? Is that giant pressure?
RYAN MANDELBAUM: Yeah. So what I saw them do was essentially you have a foil made out of the sort of doping lanthanum material. And then they used a special kind of powder that under high pressure will spit out hydrogen like protons.
And they have these little– they’re like the size of D-cell batteries. And there are diamonds at the tips of each of these halves. And they screw them together with basically Allen wrenches. And they create pressures inside between the diamond tips that are equivalent to approximately those in the Earth’s core.
IRA FLATOW: Wow. Our number, 844-724-8255 if you want to talk about this. You can also tweet us @scifri.
I want to bring on a couple of more guests to talk about people who are also involved in the research that’s doing this. I want to bring Maddury Somayazulu, Maddury Somayazulu. Sorry. Got that– butcher everybody’s name.
MADDURY SOMAYAZULU: That’s OK. Thank you. Yes, I’m glad to be on the show.
IRA FLATOW: And Eva Zurek, who is professor of chemistry at my alma mater, University of Buffalo, in Buffalo. Welcome to Science Friday.
EVA ZUREK: Thank you. It’s a pleasure to be here.
IRA FLATOW: Maddury, you’re at Argonne National Laboratory.
MADDURY SOMAYAZULU: That’s right. I am.
IRA FLATOW: Two weeks in a row we’ve had a scientist on from Argonne. That’s kind of cool.
So let’s talk about what we’re seeing here. Eva, can you tell us what is happening down on the electron level when you squeeze that hydrogen that Ryan was talking about?
EVA ZUREK: All right. So first of all, what’s really interesting is when you go to these very high pressures, what can happen is that you can get compounds that become stable that you would never have at one atmosphere, so at the Earth’s surface. So the first thing that’s happening is that you’re getting a very new type of compound that’s forming. Without pressure, you might have like lanthanum H3, for example.
But under pressure, you get this lanthanum H10. So there’s really a lot of hydrogen. And it forms this quite complex structure that’s similar to what people refer to as a cloth rate, which is a three-dimensional hydrogen cage around the atoms, the metal atoms.
And then the interesting bonding between the hydrogen atoms is just right in order to create what is known as strong electron phonon coupling. And that is the driver for the superconductivity in these systems.
IRA FLATOW: Maddury, why do you need to use diamonds? I mean, what’s the advantage there?
MADDURY SOMAYAZULU: Diamond is the hardest material known to mankind. And when you squeeze something between it, the diamonds hopefully don’t shatter. And you can subject the materials to immensely high pressures.
The only problem is that, as all of us learned in high school, pressure is force per unit area. So higher the pressure you want to go, smaller is the area you want to be at. So the tips of the diamonds are really, really small. And the samples are really, really, really small. And so therefore, we have to work at the Advanced Photon Source here in the Argonne National Labs to be able to understand what’s going on between them.
IRA FLATOW: Now, why did you choose hydrogen? I mean, years ago, people were looking at copper, were they not?
MADDURY SOMAYAZULU: Yes. But hydrogen is the material we want to understand what happens to it at very high pressures, because of the fact that there were these theories which talked about how you can metalize hydrogen at extremely high pressures. And as Eva would chime in, hydrogen is probably the most well understood molecule in the quantum mechanical world.
EVA ZUREK: Right.
MADDURY SOMAYAZULU: So that’s putting two together and trying to understand what happens with pressure on hydrogen.
EVA ZUREK: Right there was– actually, so there’s the BCS theory of superconductivity that explains a certain class of superconductors. It doesn’t explain why the copper oxides are superconducting. We still don’t really know that.
But BCS we understand. And we can use it to make predictions, therefore. And there was a prediction in 1968, I believe, that if you could make hydrogen a metal, then it would have all of the properties to be a high-temperature superconductor at high pressure.
IRA FLATOW: Hmm. And so where does the art stand, I mean the art of making this work stand? How close are we to getting that stuff that’s in between those diamonds to actually superconductor? Eva?
EVA ZUREK: Well, Zulu measured it, and it does. The problem is that it is at these very high pressures. And there are still issues. For example, the experiments are so difficult that right now they’ve only been able to measure the resistivity. And as far as I know, they do not have the perfect Meissner result data yet.
And there’s only been two labs in the world that can accomplish this feat. So it’s very difficult right now. But it’s still a proof of concept that hydrogen-rich materials have what it takes to reach potentially room-temperature superconductivity. And then the question is, how do we make these stable without pressure?
IRA FLATOW: Mm-hmm.
RYAN MANDELBAUM: And so Maddury, can you tell us a little bit about– we know that there are multiple teams working on this idea. So what has it been like to be working in tandem with these groups? I know that there’s you and then I know there’s the other group in Germany. So can you tell us a bit about that?
MADDURY SOMAYAZULU: Yeah. I mean, it’s impossible to think that we can achieve these kinds of incredible experiments working all alone in a lab like the old times used to be thought people would do. So there are these teams which come together.
And we worked at the Advanced Photon Source for many years trying to hone our techniques. And having done that, we established the first evidence for superconductivity, which were preliminary results, which were presented at Madrid, which triggered the race. And the other group at Max Planck Institute in Germany charged ahead. And a few months down the road, both of us almost simultaneously could [INAUDIBLE] with it and reshow or show the results to be consistent with each other.
And that’s great, because now we have two different groups charging ahead and trying to come up with innovative ideas about how to make these materials. And even today, we are collaborating with– a group which I work with has now spread to University of Illinois at Chicago here, to be in close proximity with us in the Argonne labs. We’re working together with them.
There are groups in University of Alabama. There is a group in National High Magnetic Field Lab in Tallahassee coming together. So it’s not something one person can do or one group can do, so a lot of these groups are coming together and trying to understand how we can make this material reproducibly and understand the physics of what’s happening, because that’s what is most important.
IRA FLATOW: 844-724-8255 is our number. We’re talking about creating superconducting devices. Let’s go to Tim in Wilmington, Delaware. Hi, Tim.
TIM: Hi there.
IRA FLATOW: Hey there. Go ahead.
TIM: Yeah. So I had a question. If you are trying to put hydrogen under high pressure in order to turn into a metal or whatnot, check its conductivity, couldn’t we just look at our sun, which is made up of hydrogen and under extreme pressure? What do we know about that?
IRA FLATOW: Oh. Somebody’s thinking.
EVA ZUREK: Should I– so we know for sure we have metalized hydrogen at high temperatures. The problem is we want to do it at very low temperatures.
IRA FLATOW: Yeah.
EVA ZUREK: And also the superconductors are going to be working presumably at not temperatures that are the temperature of the sun. So we have done those types of experiments in shock. And it is quite well believed that, for example, the core of Jupiter would be liquid metallic hydrogen.
IRA FLATOW: That’s cold.
RYAN MANDELBAUM: Yeah. So Eva, I was actually wondering, as a theoretical chemist, it’s your job to tell folks like Maddury what compounds they should be trying out. So how do you figure out the direction that you should take this research? How do we land on lanthanum hydride? And how do we know when it’s time to try and get metallic hydrogen, and what temperatures and what pressures?
EVA ZUREK: Right. So I’ve started this work about a decade ago. And I use programs that tried to solve the Schrodinger equation approximately for materials. And if you can do that, you can calculate any property of a material that you want.
And we use supercomputers. And into the supercomputer programs, we can say, OK, this is the chemical composition that we want. And this is the pressure that we want. Can you help me using various algorithms predict the most stable structure at this given composition and at this given pressure?
And I mean, it takes a long time to do these computations. But we can get the results and then calculate the properties, including estimating the superconducting critical temperature. So like I said, people have been doing these types of simulations for about 10 years. And so far, we have looked at most systems containing two elements, so hydrogen plus another element.
And at first, this kind of work is experimental, because you don’t know what’ll happen. It’s very high pressures and you don’t have an intuition. But at some point, when there was enough theoretical calculations available, there was work done on calcium-hydrogen system. And that showed that it should be a high-temperature superconductor.
And then you think, well, what’s similar to calcium? Well, you might have strontium or you might have scandium. And then computations looked at those types of systems. And also, the lanthanum and yttrium have similar properties to calcium, and so on. So people looked at that.
And actually, it was a group that Zulu collaborates with and also the group in Chicago that were the first to predict the lanthanum hydride system computationally. And that’s why they have to do it experimentally.
IRA FLATOW: I have to interrupt to say, I’m Ira Flatow. This is Science Friday from WNYC Studios. So rude of me to interrupt, but I have to get that in.
EVA ZUREK: That’s OK.
IRA FLATOW: Let me go to the phones. We have a call from Whitney in Moorhead, Minnesota. Hi, Whitney.
WHITNEY: Hello. It seems the point to be able to get superconductivity in conditions on Earth that don’t require continuous introduction of electricity, for like creating pressures and stuff. So when you’re talking about all this high-pressure conditions, aside from we need more volume if we’re going to make this practical, we also need it seems like an exception to the whole temperature thing, because obviously high pressure is not– continuous high pressure is just going to take more electricity than it’s going to save.
IRA FLATOW: OK. So any reaction?
RYAN MANDELBAUM: Yeah. How do we make it useful?
IRA FLATOW: Yeah. How are you going to get it out of that pressure cooker you have it in?
MADDURY SOMAYAZULU: Yeah. I would say that– whenever anybody asks me about this, I point to one of the greatest things in nature. Graphite converts to diamond under pressure. But if we can find a way of using diamond– or we all want to use diamonds. We have found ways of creating it in other ways, quenching the diamond state at lower pressures.
So I would say going forward, of course, we still have to understand the physics of what’s going on here. And we have to go back to people like Eva to increase their calculations to predict other complex systems, where we could lower the pressure or we could quench them to atmospheric pressures, like diamond is quenched to atmospheric pressure and is stable. And then you have a situation where you can make a practical material, which we can use.
RYAN MANDELBAUM: So we’re not quite at– I mean, I know that we’ve demonstrated basically evidence that these lanthanum hydride systems are superconducting now. And so before we even think about turning down the pressure, Eva, what steps do we actually have to go through to get to the level where we’ve totally convinced ourselves that we’ve created a room-temperature or near-room-temperature superconductor?
IRA FLATOW: Eva, I’m going to ask you to wait for that answer, because we have to take a break.
EVA ZUREK: Sure.
IRA FLATOW: It’s always something. Stay with us. We’re talking about superconducting with Maddury Somayazulu. And also we’re talking with Eva Zurek. And we’re answering your questions on Science Friday. 844-724-8255.
Stay with us. We’ll be right back after this break.
This is Science Friday. I’m Ira Flatow. We’re talking this hour about the search for superconductors. My guests are Ryan Mandelbaum, science writer for Gizmodo, sort of serving as my partner today. Maddury Somayazulu is a group leader of the X-Ray Science Division at Argonne National Lab in Lemont, Illinois.
Eva Zurek is a theoretical chemist and professor of chemistry at the University at Buffalo. Our number, 844-724-8255. And Dr. Zurek, when I rudely interrupted you, you were about to answer the question for us.
EVA ZUREK: That’s all right. So the question was, what do we need to do to prove the superconductivity in the [LAUGHTER] hydride system, I believe. So the experimental groups, they have shown the drops in resistivity, the disappearance of the resistance.
And the other thing that needs to be shown is something called the Meissner effect. So when you put– when a superconductor is put into a magnetic field, it expels the magnetic field. And that’s what lets you have these levitating trains, for example, that go on superconducting tracks.
And it has published on the archive, the change in the superconducting critical temperature with the magnetic field. But as far as I know, the Meissner effect has not yet been published. I know that Zulu is working on it. I don’t know how far that has gotten. But that’s something that needs to be demonstrated.
IRA FLATOW: Mm-hmm. Let’s go to the phones, to– why was I going to go to the phones, though?
Let me ask you this question. There was a call there and somebody who dropped off the phone line about graphene. There was research– I know Ryan, we were talking about this– published this week that take two sheets of graphene and sort of twist them around and there is superconducting spots on them. Did I get that right, close at all? Is graphene a good candidate, Eva, for using superconductivity?
EVA ZUREK: So from what I know about this topic– it’s not my main research– but you need to have a very precise angle of rotation between the two graphene sheets, of about 1.1 degree. And I do not think the TC is that high.
I think that people find it extremely interesting. Also, this was first theoretically predicted before it was experimentally shown. But I don’t think it’s going to reach room-temperature superconductivity, as far as I can tell.
IRA FLATOW: Hmm.
RYAN MANDELBAUM: I think what I’m wondering is how not just graphene but also lanthanum hydride and other kinds of superconductors we’re not talking about tie into the bigger picture. I mean, is there going to be a future where there’s just one kind of superconductor or how will that look?
IRA FLATOW: Maddury, you want to weigh in on that?
MADDURY SOMAYAZULU: Yeah. I think, mean, if you look at technology today, almost every superconductor we talk about, which is being used in let’s say MRI machines or in magnets and other places, is niobium-tin. And for a variety of reasons, it was the material of choice, although it doesn’t have the highest superconducting transition temperature.
So I think going forward, the way I would look at it, into the future is that there are a lot of materials which we will discover based on these kind of materials which we have recently discovered. And of these, technology will choose the one which is most should I say cost-effective. It may not necessarily be room-temperature superconductor. But even if it’s superconducting at let’s say in a Siberian winter, it’s still a better superconductor than having something at such low temperatures.
IRA FLATOW: [LAUGHTER] Well, Maddury, what would be room temperature? What number would we say, hey, it’s truly room temperature?
MADDURY SOMAYAZULU: As I understand, if you can make something superconducting at about 300-plus kelvin, which is about let’s say 25, 30 degrees centigrade or so on, that’s the proper temperature to work with.
IRA FLATOW: That’s hotter than room temperature. That’s like almost 85, 90 degrees Fahrenheit, something like that.
MADDURY SOMAYAZULU: Yeah. The reason why you want it to be higher than room temperature is for simply the reason that if there is a collapse of superconductivity, there are a few strands of the superconductor which stop being superconducting, they will become normal. They will start heating up. Then the rest of these superconductors would collapse.
So if I [INAUDIBLE] such a wire, a superconductor of whatever this material, which is going to be room-temperature superconductor, it should be superconducting well above room temperature to make it technologically useful at room temperature.
RYAN MANDELBAUM: And what temperature are we at now? And what temperature do present theories say we can go to?
MADDURY SOMAYAZULU: With lanthanum hydride, we have seen nebulous signatures of superconductivity even as high as 280 kelvin, which is roughly– which is almost close to room temperature or a little above normal room temperature, I’m saying. But the theory predicts other materials– if I remember right it’s yttrium hydride and others–
EVA ZUREK: Yeah.
MADDURY SOMAYAZULU: –which would be superconducting at 320 Kelvin, which is about 40 degrees above room temperature.
EVA ZUREK: That’s right.
MADDURY SOMAYAZULU: So that would be the kind of materials to look for.
IRA FLATOW: Eva, did you want to weigh in there?
EVA ZUREK: Yes. The highest prediction that I knew is for yttrium H10. That is at about 325 kelvin, 250 gigapascal’s.
IRA FLATOW: Mm.
RYAN MANDELBAUM: Got it. And actually, Eva, kind of moving to the bigger picture, we had a question which was just, we’re asking some of the most basic science questions here. And I come and talk about theoretical physics with Ira. We talk about dark matter. So what are some of those biggest mysteries right now in this field, in theoretical chemistry? I mean, what are some of the biggest outstanding questions that we’re working towards?
EVA ZUREK: I guess for these types of superconductors, the question for me is, you have these different structures with the way that hydrogen is arranged. And we’re seeing that these three-dimensional cage-like structures only appear in certain types of combinations with certain elements. Why?
And why is it that you need these geometries to get this very high TC? You don’t get it when you have stuff with H2 units in it. You just don’t get that high TC. So what’s special about that?
And if we can understand that, then we can use that knowledge to try to engineer other materials that might be stable at lower pressures or meta-stable, like Zulu said. If you take off the pressure, it won’t decompose.
IRA FLATOW: I’m glad you guys are working on that, because we’ll have to end it right there. I want to thank my buddy in the studio with me, Ryan Mandelbaum, science writer for Gizmodo. Thanks for–
RYAN MANDELBAUM: Always great to be here. Thanks for having me. I love it.
IRA FLATOW: Always great to have you.
Maddury Somayazulu is group leader of the X-ray Science Division at Argonne National Lab in Lemont, Illinois. And Eva Zurek is a theoretical chemist and professor of chemistry, University at Buffalo. Thank you all for taking time to be with us today.
EVA ZUREK: Thank you.