[Reading Science] The Movie Avatar's 'Floating Island', The Secret of Superconductors

Active Research on Room-Temperature Superconductors with Zero Electrical Resistance
"Maximizing Energy Efficiency, Foundation for Future Technological Innovation"

The movie ‘Avatar 2 - The Way of Water’ has recently surpassed 10 million viewers in South Korea and is gaining popularity worldwide. Although it is a film based on various scientific knowledge, studying superconductors is essential to understand the basic storyline. The era is a distant future where humanity has exhausted all usable energy resources on Earth, such as uranium. Humanity invades the alien planet Pandora to mine a very rare and expensive resource with room-temperature superconducting properties called ‘Unobtanium.’ The floating ‘islands’ in the movie are the actual form of Unobtanium. Due to the Meissner effect, one of the main properties of superconductivity, it repels other objects and floats in the air. Unobtanium is a neologism often used in sci-fi movies and novels to mean an ‘unobtainable resource,’ signifying its tremendous value. Its most significant feature is that it possesses room-temperature (or high-temperature) superconductivity. While nuclear fusion technology is a means to produce clean and pollution-free energy for humanity’s sustainable future, room-temperature superconducting technology is the foundation that can utilize the energy of resources over 100% and commercialize currently impossible future technologies.

What is a superconductor?

The end of humanity is approaching. If you could pass down only one piece of knowledge to future generations, what would it be? Richard Feynman, a leading physicist at Princeton University in the 1980s, famously chose the phrase, “Everything is made of atoms.” This statement contains the foresight that understanding the atomic world is the key to saving humanity. One representative atomic technology is room-temperature superconductor technology. Although superconductors have been used before, they require cooling to at least below -100 degrees Celsius using liquid helium or nitrogen, which involves enormous equipment and costs. If superconductivity could be utilized at room temperature, it would enable revolutionary technological innovations in many application fields. Since the discovery in 1911 of the superconducting phenomenon where electrical resistance drops to zero at a critical temperature near absolute zero (0 K, -273.15°C), humanity has been striving to develop such room-temperature superconductors (Superconductors).

▲A superconductor running while levitating in the air

First, let’s understand the concept and principle of superconductors. Materials in the world can be divided into conductors, which allow electricity to flow well, and insulators (dielectrics), which do not. There are also semiconductors like silicon, which behave in between. By adding impurities or applying an electric field to insulators, electricity can flow. In contrast, superconductors have zero electrical resistance. There is no loss during transmission, and no heat is generated. They also exhibit the phenomenon of repelling magnetic fields (Meissner-Ochsenfeld effect). To prevent magnetic fields from entering the material, an opposing magnetic field forms on the surface, causing mutual repulsion?this is the principle behind magnetic levitation trains. The Josephson effect also appears, where superconductivity is induced when in contact with other materials. This superconducting phenomenon occurs because two electrons pair up to form a Cooper pair depending on temperature and pressure. When Cooper pairs form, the internal electrical resistance becomes zero. It is similar to converting a congested road into a one-way street, eliminating traffic jams. This was accidentally discovered in 1911 by Dutch physicist Kamerlingh Onnes during an ultra-low temperature experiment using liquid helium.

Room-temperature superconductors, the foundation of the future

The problem is that inducing superconductivity requires enormous equipment and costs. The currently developed quantum computers, which are the size of an entire building, are a prime example. To allow quantum particles to move freely, superconductivity must be used, but to lower the temperature to the critical point (absolute temperature 4.2 K), massive cooling devices using liquid helium and nitrogen, as well as vacuum and zero-gravity equipment, are essential. Scientists are striving to overcome these limitations by developing materials that maintain superconductivity even at room temperature, i.e., high-temperature superconductors. What would happen if a material that maintains superconductivity without additional equipment, resources, or costs were developed? The ‘Unobtanium’ from the movie Avatar could be recreated on Earth. The efficiency of electricity generation, storage, and transmission could be maximized. ‘Palm-sized’ quantum computers, ultra-low power semiconductors, sleek and fast spaceships like those in the movie Star Trek, and the commercialization of magnetic levitation trains?which have been delayed due to high costs and resource demands?could become reality. Transmission and storage devices (batteries) with zero power loss would be developed. Tremendous electricity could be generated through ultra-small generators that minimize inefficiencies in wind, tidal, and nuclear power. Magnetic resonance imaging (MRI) machines in hospitals would also become very affordable.

Urgent need to clarify the principle

In 1986, a material exhibiting superconductivity at an absolute temperature of 35 K using copper oxide was discovered. In 2008, superconductivity was achieved at 21 K in iron oxide-based materials. Particularly, in 2020, a research team at the University of Rochester in the United States announced the discovery of a material exhibiting superconductivity below 15 degrees Celsius, causing a stir in the physics community. The team succeeded by placing carbon, hydrogen, and sulfur between two diamonds and applying enormous pressure (2.6 million times atmospheric pressure) using lasers. However, about a year later, in November of last year, the publication was retracted amid allegations of data manipulation, sparking controversy over the experimental results. The key issue is to clarify the principle of high-temperature superconductivity. Scientists still only know that arranging particles in a lattice structure can induce high-temperature superconductivity but have not identified the exact cause. This is similar to how much of quantum mechanics only understands phenomena without answering the questions “why?” and “how?”.

Professor Lee Gil-ho of the Department of Physics at Pohang University of Science and Technology said, “The problem is that we have no clue how to create materials with higher critical temperatures because we do not know the exact reason why high-temperature superconductivity occurs.” He added, “The known critical temperatures of high-temperature superconductors are roughly between -250 and 100 degrees Celsius, but to raise this to above zero degrees Celsius, we must first understand why this high-temperature superconductivity occurs and design materials with higher critical temperatures based on that. This is the theoretical limit.”

▲Changes in nesting conditions before and after alkali metal surface deposition on iron-nickel chalcogenide superconductors.
[Photo by IBS]

Active research in South Korea

Professor Han Seung-yong of the Department of Physics and Astronomy at Seoul National University, selected as ‘Scientist of the Month’ in 2021, developed technology to miniaturize superconducting magnets. To improve the phenomenon where superconducting magnets used in generators burn out at high capacities, he created an ‘insulation-free high-temperature superconducting magnet.’ This was a new technology that could reduce the size of conventional superconducting magnets to 1/100th. Currently, the government is investing 46.4 billion KRW over five years since last year to advance and commercialize this technology through a high-temperature superconducting magnet research and development project. Professor Han said, “The insulation-free technology is a concept where electrons jump to empty side paths before colliding and generating heat. The superconducting magnets used in the International Thermonuclear Experimental Reactor (ITER) construction are over 20 meters long, but this technology can reduce them to within 3 to 4 meters. It can be applied in many fields such as bio, medical, defense, and urban mobility.”

Research to understand the principles of high-temperature superconductivity is also active. Kim Hyun-tak, a senior research fellow at the Electronics and Telecommunications Research Institute (ETRI), attracted international attention in 2021 by developing a formula to calculate the critical temperature that can explain superconductivity phenomena. This theory could explain low-temperature, high-temperature, and room-temperature superconductivity. Professor Kim Chang-young of the Department of Physics and Astronomy at Seoul National University also demonstrated in 2017 that high-temperature superconductivity can be realized in both electron-doped and hole-doped materials.

Professor Kim Yong-kwan of the Department of Physics at KAIST said, “The key to developing high-temperature superconductors is to identify the mediator of Cooper pairs, i.e., the interaction between electrons.” He pointed out, “Since this is fundamental science, the overall level of solid-state physics must be elevated to understand everything. In South Korea’s case, although it is difficult to lead, we should build a foundational infrastructure and collaborate with the international scientific community.”