Brain behind Metallic Hydrogen: Pressing on Pressure | Daily News

Brain behind Metallic Hydrogen: Pressing on Pressure

Harvard University’s Professor Isaac F. Silvera and Dr. Ranga P. Dias, a Sri Lankan post-doctoral researcher, reported in the Journal Science on January 26th that they have succeeded in creating metallic hydrogen, a substance that has been sought after for around 80 years.

The discovery of metallic hydrogen could revolutionise transportation, electronics, and power systems if it is proven to be a superconductor and stable at room temperature and normal pressure, as has been theorized.

Born in Kottawa, Dias spent his childhood and early adult life in Sri Lanka before moving to the United States to pursue a PhD in physics. He is 36 years old and has been working on the metallic hydrogen project at Harvard for the past three years.

The following is an interview with Dr. Dias.

Q: How did you get interested in condensed matter physics?

A: That’s a good question to start with. At an early age I was exposed to the term superconductivity. I was a member of an astronomical society in Sri Lanka called the ASSC, or Astronomy and Space Study Center, which is located near the University of Moratuwa. I joined that club when I was 13 years. In that society they do a lot of astronomy and astrophysics. People from all sorts of scientific backgrounds, whether it’s mathematics, chemistry, or physics, meet at the ASSC and learn from each other. It doesn’t matter how old you are, the people there listen to lectures, hold observation sessions, and solve problems together. They had a physics cycle where senior members of the society, who were university students at the time, discussed big problems in physics. So I was exposed to these discussions from an early age, and this superconductor thing always struck me. I felt it would be a neat thing to work on, to see if you could really find a superconductor at room temperature.

Q: What is a superconductor?

A: We say superconductors are substances that conduct electricity without any resistance. So far, nobody has found a superconductor that works at room temperature. They do exist but only at very low temperatures. If we can find one that works at room temperature, that could really revolutionise our way of life. To find one of these, you have to study condensed matter physics, and I’ve always been focused on that.

Q: Can you tell me how you got from the University of Colombo to Harvard?

A: So, I wanted to do condensed matter physics, but I really wanted to do it quickly. In Sri Lanka, we go to university when we are 20 or 21, by the time we finish our undergraduate studies we are 26. So, I applied when I was in my third year at Colombo to graduate programs so that by the time I finished my fourth year I could quickly start my PhD. I graduated in July, and then in August I moved to the United States to do my PhD at Washington State University. At the time, it was considered one of the best universities for extreme condensed matter physics. These are the people who do experiments with extremely high pressure.

My PhD was very successful. I was able to find a new superconductor. It is the simplest molecular superconductor: carbon disulfide. It’s just a liquid, but I was able to transform it into a superconductor at a very low temperature, like 6 or 7 Kelvin. People knew about my work, and I got some attention from the scientific field, and then this Harvard group found out about my work, and they invited me to come and work on hydrogen. So that’s how I ended up there. They actually asked me to come three times, but the first two times I had some other commitments. But the reason I went is that Harvard is very famous for its research on hydrogen. Professor Isaac Silvera, my current adviser, is one of the pioneers in low temperature physics, and he has been studying hydrogen for quite a while. If you really want to study hydrogen physics, Harvard is the best place to go.

Q: Can you take me through the process of discovering metallic hydrogen?

A: Yeah. The recipe is kind of already there. People predicted this more than 80 years ago. It’s just a matter of figuring out the correct pressure to make it happen. In a room temperature and normal pressure setting, hydrogen is a gas with molecules that are very, very far apart from each other. So, if you squeeze hydrogen molecules together, then at some point you can dissociate those molecules, and you will have the proper electron arrangement that can conduct electricity. So for that, you have to bring the molecules together by squeezing them hard, and you have two different options to generate really high pressures. The first is creating a shockwave from which you can calculate the pressure exerted on a substance. The other option is to create mechanical pressure by squeezing substances together. This is static compression. Shockwaves only last for very short periods of time, like milliseconds or nanoseconds. But in static conditions, you can have all the time you want.

A lot of materials can go through the transition from gas to solid, such as both oxygen and xenon. Hydrogen is special, though, because it has new exciting and exotic properties. It is a superconductor at room temperature and can also be a superfluid, which is similar to a superconductor, but it can also flow without any resistance. These are highly energetic materials that have the potential to revolutionise the transportation industry and rocket propulsion. That’s why people have wanted to create metallic hydrogen for such a long time. The problem we had was getting there, but we were able to come up with a new technique to somehow achieve the necessary pressure. To get to these higher pressures, we used an apparatus like a nutcracker called a diamond anvil cell. We took two diamonds and placed hydrogen molecules between them. We use diamonds because they are the strongest material that we know of, and also because they are transparent. The transparency allows us to do x-ray and spectroscopic studies, which are very important for our work. So we used that method to generate these higher pressures. But the problem with hydrogen is that it is very diffusive. It can actually go into the diamond and break it. These diamonds, though they were very nicely polished, had a few surface defects when viewed through an atomic microscope. We were able to come up with new techniques to remove these defects. For example, we put a special coating on top of the diamonds so that hydrogen would not diffuse into them. So that gave us an edge to achieve these high-pressure conditions.

Q: How many people worked on this?

A: Just my adviser Professor Isaac Silvera and I worked on the project.

Q: Can you talk about the applications of metallic hydrogen outside of space flight? Why is this discovery so significant?

A: Huge potential lies in its superconductivity. If you really could turn this into a room temperature superconductor, as has been predicted, then you could make wires out of metallic hydrogen that would conduct energy without any dissipation. Right now, if you want to send electricity from the East coast of the US to the West coast, you could lose at least 60 percent of the energy because of the resistance within the wires. But with metallic hydrogen superconducting wires, then you will not have any energy losses. Superconductors also have a property called diamagnetism, which means that, if you put a magnet on top of one, the magnet will float. So you can make magnetically levitated high-speed trains. Right now, you have to cool superconductors down to make them work, but if you can find one at room temperature, transportation will change. Also, the best way to store energy is in superconducting coils. If you store a current in a superconducting coil it will stay there basically forever. There’s no decay, so this would be the best way to store energy. You can think of this technology as an improved battery. It could revolutionise cell phones and any other device that uses a battery. Electronics, transportation, and power systems could all change due to this discovery.

Q: Do you think that the metallic hydrogen will be stable at room temperature with regular pressure?

A: The calculations say that it should be metastable, meaning that it should be like a diamond. Let me give you an example. Graphite is the most stable form of carbon at room temperature and pressure. But if you take graphite and squeeze it very hard, it will turn into a diamond. And then once you release the pressure, the diamond stays there and does not revert to graphite. Hydrogen has this exact same property and has a large activation barrier to go back to its original form. That’s the beauty of it. People can think, okay, if metallic hydrogen is only stable under pressure, what’s the use of it? But we have calculated that it should be stable at room temperature.

Q: Right now, the sample of metallic hydrogen is still under pressure?

A: Yes, that’s correct.

Q: When do you think you will take the pressure off of it?

A: Pretty soon, probably in the next couple of months. We wanted to do X-ray studies too. So after that we will test the metastability.

Q: What do you see as your next project?

A: After testing the metastability and the doing the X-Ray studies, we are planning to test its superconductivity, which is the main property everyone is excited about. So for that it’s going to be somewhat challenging. The sample we are talking about is very small, about 1/10th the width of a human hair. You have to put tiny electrodes onto the sample and measure it. One of the problems is that we use this metal gasket to load the hydrogen into the diamond anvil cell, so we have to find a way to use an insulating gasket instead of a metal one. Otherwise you short the electrodes.

Q: Do you see this being cost-effective in the long term?

A: Yes, I would say so, because I think we can find a way to make this happen in large quantities. The only problem is we need to come up with another method of making metallic hydrogen in large quantities. I have some ideas, but we still need to make them happen. There’s also an unlimited supply of hydrogen gas in the atmosphere.

Q: Do you see yourself collaborating with Sri Lankan scientists in the future or moving back here to teach in the near future?

A: I’m really interested in collaborating. I don’t see myself moving back in the near future because the type of research I do at Harvard is quite expensive and needs a lot of funding. I’m not sure if there’s that level of support in Sri Lanka. But I do believe I can make a bridge between Sri Lanka and here by collaborating with people. There are some experiments that we could do together. For big projects, many small experiments must be done, and maybe we can collaborate on these and do some of the small-scale tests in Sri Lanka. I would also like to guide and teach young scientists. Perhaps we can look into creating joint PhD programs. That’s something I really want to push.

Add new comment