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Sri Lankan pioneering superconductivity research
Prof Ranga Dias and team make world’s first-ever room-temperature superconductor
By Sajitha Prematunge
It is not a vaccine for COVID-19, but it could be the next best thing. The world’s first superconductor at room temperature, developed by a research team lead by Sri Lankan born physicist, Prof. Ranga Dias at the University of Rochester, USA, could potentially revolutionise everything from transport to energy industry.
The team recently discovered carbonaceous sulphur hydride (CSH), a new compound that acts as a superconductor at 15 °C at a pressure of 267 Giga Pascals (Gpa), or 2.6 million atmospheres (75 percent of the pressure at the earth’s core). The heady article in Nature magazine, which published this groundbreaking discovery in its cover story on October 15, may sound gobbledygook for some. Consequently, The Island interviewed University of Rochester, USA, Department of Physics and Astronomy and Department of Mechanical Engineering, Assistant professor Prof. Ranga Dias; Ph.D. student in Physics, Hiranya Pasan and Ph.D. candidate in Optics, Ashan Ariyawansa to put things in perspective.
A superconductor is a materiel that poses no electrical resistance. “We used two diamonds, each approximately 150 to 200 micron in diameter, on top of each other, to make what’s called a diamond anvil cell. The sample was sandwiched between the two diamonds and pressure applied.” Pasan explained that they could achieve pressures of up to 500 Giga Pascals with the diamond anvil cell. “For comparison, that’s more than the pressure at the earth’s core,” said Pasan. “The diamond anvil cell acts as a materiel search engine, that we use to test material at different pressure until we found the ideal conditions to achieve superconductivity for each material, allowing us to determine which materiel is the most effective. And the result was CSH, a compound belonging to a new class of dense hydrogen rich material.
What took so long?
Pressure variations can convert basic elements of the periodic table into something completely different. Dias explained complex high-pressure physics with a simple analogy. There are two people in a room who can’t interact with each other because they are on opposite corners of the room. Now have the walls close in on them until they are able to talk, shake hands and interact. “The same principle can be applied to elements. When pressurized, atoms and molecules become more interactive and make new bonds. This alters the actual chemical nature of the compound. That’s the beauty of high-pressure physics, it allows you to manipulate the identity of compounds to create whole new material with completely unexpected properties,” said Dias.
Previous research
Dias holds a Bachelor of Science degree from the University of Colombo. He turned his attention to metallic hydrogen research as an extension of his PhD research on high-pressure physics at the University of Washington. In 2017, Dias, then a postdoctoral fellow at Harvard University and Isaac Silvera, physicist at Harvard announced the discovery of metallic hydrogen in the Science magazine. Their experiment involved compressing hydrogen gas, which liquifies when cooled to minus 423 degrees Fahrenheit (minus 252.778 Celsius), and then solidifying it at lower temperatures. The claim came under heavy criticism for being based on a single observation, on reflectivity (an expected signature of metallic hydrogen), and without a direct measurement of the pressure involved. The original ‘metallic hydrogen’ sample was lost during the subsequent failure of the diamond anvil cell. Prof. Dias said: “It was a complete study. What is left is to describe the properties of metallic hydrogen, which we are actively working on. Research takes time. None of these experiments are easy.” He joined the University of Rochester, in 2017 as a professor, and is currently conducting further research on metallic hydrogen. He further explained that the Harvard group measured the pressure directly using standard methods that any high-pressure scientist used. Every high-pressure experiment ended with the failure of the diamond anvil cell, which means the loss of the sample. Consequently, Dias argued that there was nothing unusual about the fact that their diamond broke, resulting in the loss of the sample. “I think fellow competitors who were trying to make metallic hydrogen wasn’t happy that we got it right, their criticism has nothing to do with science but rather was a political attack on my previous advisor [Silvera].”
When asked how positive he is about the newly discovered carbonaceous sulphur hydride, in light of the previous backlash, Dias said that he doubted there was a connection. “They are two different experiments and very different samples. The hallmark of superconductivity is the complete absence of electrical resistance. And another property of superconducting materials is that when it is cooled below the superconducting transition temperature, the magnetic field lines are expelled from the material. We have observed both of these key properties on our carbonaceous sulphur hydride materials at high pressures.” Dias confident of the results.
Prof. Dias’ finding has definitely sparked investor interest. In fact, investors are already lining up to fund a research company, by the name of ‘Unearthly Materials’, set up under the leadership of Prof. Dias to carry out further research and to manufacture superconductors on a large scale. A financial capital of US $ 2 million, has already been provided by investors. Dias hopes it will culminate in a highly productive venture in three to five years.
Implications
Prof. Dias believes that the technology could open up a world of possibilities for medical imaging such as MRI, computing and consumer electronics such as mobile phones. Applications of his discovery include low-cost MRI scanners, magnetic levitation trains, and power lines with no electrical resistance. “A computer, for example, has a heavy cooling system with heat sink, fans and the like, but with a superconductor none of these will be necessary,” explained Hiranya Pasan, who was tasked with low temperature analysis in this research. With this kind of tech everything from car radiators to train tracks could become redundant. “A huge amount of energy is lost in transmission per year. It adds up to a lot of money,” pointed out Pasan. So, if someone were to mass produce superconducting wire, which offers no electrical resistance, he would save billions of or dollars for countless governments.
And then there is the Meissner effect, which in layman’s terms means to repel a magnet. Superconductors are strongly diamagnetic and expel magnetic fields. As such trains could employ magnets that levitate on superconducting material. “It produces no friction,” explained Pasan. Such frictionless high-speed trains could revolutionise the transport sector.
“The technology already exists,” explained Dias. Superconducting technology is used in MRI scanners, particle accelerators, and magnetic levitation trains of experimental scale in Japan, all of which involves large magnetic fields. “But it requires cryogenics.” Meaning that some metals reach superconductivity at extremely cold temperatures and, therefore, have to be cooled to about 10 to 20 Kelvin. For context, that’s minus 263.15 to 253.15 Celsius. The critical temperature of the first superconductor, discovered in 1911, was minus 269 °C, and the fact that no research has ever been able to find a material that acts as a superconductor in room temperature has been one of the major challenges in physics.
“The cryogenic factor is what makes the technology so expensive and therefore economically unviable,” pointed out Dias. So, if cryogenics were to be taken out of the equation, it would make medical imaging, for example, much more affordable and efficient. Prof. Dias explained that liquid helium is the most widely used coolant in superconducting applications, a resource fast diminishing.
He and his team were able to take the cryogenics out of the equation, but maintaining such gargantuan pressures make mass production of superconducting material virtually impossible. When asked how stable the new compound was Dias explained that CSH could be metastable, meaning that it may not revert to the original compound of carbon and sulphur once pressure is relieved. If not, it’s back to square one for the team as they would have to find another compound that acts as a superconductor at both room temperature and atmospheric pressure. The team revealed that they would conduct the ultimate experiment by relieving pressure, in the weeks to come, which Pasan has been tasked with. “Once we have a metastable superconducting material at ambient pressure, it’s just a matter of replicating it, using techniques like chemical deposition and Molecular-beam epitaxy (MBE), to achieve mass production.” Those were the standard techniques and therefore were affordable, he said.
Ground-breaking discoveries are made every few decades in the western world and they have little or no effect at all on developing nations such as Sri Lanka. So why is a superconductor at room temperature even significant for a country like Sri Lanka? “I don’t think that the GDP matters in terms of implications of such discoveries, said Dias. “What is rocket science is developing a superconductor at room temperature. When that’s a reality, application comes easy. Whether it was frictionless trains or MRI scanners, such technology can always be applied by replacing the existing technology with the new.”
Application of such technology in quantum computing would be difficult for a country like Sri Lanka, but Dias pointed out that the implications of the technology for energy transmission was of considerable significance to developing countries. As Pasan pointed out, a lot of electricity is lost during transmission. Dias argued that with a superconducting wire, that pose no resistance, third world power generation can be made more efficient, thereby increasing capacity. “This kind of application is not difficult to apply even in a developing country.” Dias assured that such technology would be affordable even for developing countries.
Local students
When asked about the practical difficulties Sri Lankan students have to face, Hiranya pointed out that as opposed to Sri Lanka, the US has a more student-centred education system, while Dias said there was a clear lack of enthusiasm for research in Sri Lanka. “During my time in Sri Lanka, we were hardly exposed to experiments, we rarely saw instruments, except at practicals during undergraduate years, simply because we didn’t have the facilities,” said Prof. Dias. “The system is exam-oriented, and as a result we lacked hands on experience.” Dias pointed out that in the US education system there was ample opportunity for research. “Even the exam questions here are very practical. It hones critical thinking instead of promoting memorising equations and just getting good grades.” Such a system increases research productivity, he said.
“Research lacks support in Sri Lanka, especially in terms of funding,” said Dias. “In the States we can acquire federal, corporate and other sources of funding. But in Sri Lanka we don’t have that kind of a mechanism.”
But things are looking up, said Ariyawansa. “Collaborative research on chemistry and biotechnology is undertaken increasingly in Sri Lanka,” he said, pointing out that industrial chemistry and nanotechnology were fast developing areas, but he admitted that physics was still lagging behind. “We now have institutions such as SLINTEC [Sri Lanka Institute of Nanotechnology], which has succeeded in attracting a lot of expatriate academics back into the country,” added Dias. He opined that such infrastructural support and funding would facilitate cutting-edge research.
When asked whether such cutting-edge research would have any practical applications in Sri Lanka and whether putting so much money and effort into research was viable in the absence of practical applications, Prof. Dias said that there would always be opportunities in terms of putting research into practice. “Commercial production of graphene by SLINTEC is a case in point. It’s a direct application. I’m sure that if Sri Lanka can produce high grade graphene, we can export it. Graphene has a lot of applications, especially in electronics. It’s used widely in the US, Japan, Europe and South Korea for semiconductor and mobile applications.”
The same principle can be applied to diamonds. “With the right combinations of material diamonds can be grown in the lab,” Dias pointed out that this could revolutionise the diamond industry. “This is already being done in the US,” said Dias, reiterating that material research would always have applications.