Edited by Ryan Jien.
What are superconductors?
Up to 15%¹ of all energy in transmission lines, electrical appliances and transport is wasted through heat loss during energy transfer. But what if there was a way for that to be zero? Superconductors, first discovered by the physicist Heike Kamerlingh Onnes in 1911, have captivated the minds of scientists and engineers with their amazing ability to conduct electricity with zero resistance. We will dive into the mesmerising world of superconductors, exploring the reasons behind their behaviour, the ways they can be used, and the search for superconductivity at room temperature.
How does it work?
Superconductivity is achieved when certain materials, usually metals and metal alloys, are cooled to extremely low temperatures as near as absolute zero (-273.15 degrees Celsius). Below a material’s specific critical temperature, it goes from its normal resistive state to a superconducting and non-resistive state. This is because in the superconductive state, electrons make pairs—Cooper pairs—which overcome the usual repulsive forces of the metal’s lattice vibrations (phonons). These pairs of electrons move together through the crystal lattice and coordinate with the vibrating nuclei, resulting in no collisions thus no resistance.
The Meissner effect
In addition, superconductors also display the fascinating Meissner effect. This is when a superconductor, in the presence of an external magnetic field, expels all magnetic flux lines from its inside. Superconductors set up small currents near its surface, creating a magnetic field in the opposite direction, which acts as a shield that prevents outside magnetic fields from penetrating. Now, it is the perfect diamagnet – the superconductor creates a magnetic field in the opposite direction, causing repulsion, so a magnet on top levitates.
Types of superconductors
There are two types of superconductors: type I and type II.
Type I superconductors are identified by an abrupt and direct transition into the superconducting state. They are typically pure elements and display the Meissner effect strongly. Yet, they have limitations to the strength of the magnetic field they can deal with and usually have very low critical temperatures, so they are less practical.
Type II superconductors on the contrary have a more gradual transition to the superconducting state and can tolerate much higher magnetic fields. However they can have vortices (magnetic flux lines that can penetrate the material), which cause localised resistance; this is when a small part of the superconductor displays electrical resistance and loses its superconducting properties, leading to energy loss and reduced efficiency.
The practical uses of superconductors
The many unique properties of superconductors mean that they have a variety of applications across a range of fields:
Magnetic Resonance Imaging (MRI): Superconductors generate high magnetic fields that provide rich detail and non-invasive medical imaging that is swift and of high quality.
Magnetic levitation (Maglev) Trains: Maglev trains can float above the track which reduces friction and allows for high-speed, energy-efficient transportation.
Particle accelerators: The high magnetic fields generated by superconductors help to accelerate and steer particles with paramount precision allowing scientists to study subatomic particles and important forces like strong nuclear force and electromagnetic force.
Power transmission: Superconducting power cables can carry much higher loads of electricity with much less energy loss, making long-distance transmission more efficient & environmentally friendly.
Multi-Role Wonders
Nanotechnology:
Nanowires: Superconducting nanowires are used as highly sensitive detectors that measure the number and energy of photons (tiny particles of light). They are critical for quantum information processing, as they provide secure communication and can be used at extremely low temperatures to figure out how much power a particle has.
Astrophysics:
Cosmic microwave background studies: Superconducting detectors are used to study Cosmic Microwave Background radiation. They can precisely measure temperature fluctuations in the CMB, providing insight into the early state of the universe and its evolution.
Gravitational wave detection: Superconducting materials are used in the making of superconducting radiofrequency cavities in gravitational wave detectors like the LIGO (Laser Interferometer Gravitational-Wave Observatory) – instrumental in detecting ripples in spacetime caused by cataclysmic astrophysical events.
Quantum mechanics
Quantum computing: Quantum bits or qubits (the basic unit of information in quantum computing) in quantum computers rely on superconducting circuits. These circuits exploit the quantum properties of superconductors like their ability to carry current without resistance² and exhibit quantized energy levels, which creates stable and coherent qubits for quantum energy processing and make quantum behaviours more obvious.
Quantum levitation: As they display the Meissner effect, leading to the expulsion of magnetic fields, they can be used for quantum levitation here superconductors are suspended in a magnetic field without any contact, creating possibilities for precise motion control and transportation of particles in a frictionless environment allowing for further research.
The road ahead
Even though there is a lot of groundbreaking potential in the world of superconductors and optimism for the future, we should always be sceptical of new findings.
According to an article from CNET³, in late July South Korean scientists reported a potential breakthrough in superconductors, claiming the discovery of one that could work at an ambient temperature⁴. The superconductor, called the LK-99, has been described as a "modified lead-apatite structure doped with copper”.⁵ Even though it has sparked excitement and furthered research into the matter, the results should be taken with a grain of salt, says Xiaolin Wang, a material scientist at the University of Wollongong, and that the findings should not be hyped “until more experimental data is provided”. Michael Norman, a theorist at the Argonne National Laboratory, remarked that flaws in the experimental data made the scientists “come off as real amateurs”.⁶
So why did the LK-99 show this superconducting behaviour? One explanation could be the nature of the chemicals involved in the LK-99 which makes it hard to identify whether its behaviour is from the LK-99 itself, or other chemicals, impurities and contaminants within. One such impurity, cuprous sulphide, which experiences a large (but still non-zero) drop in resistance at 127°C, may have led the researchers to interpret this as superconductive behaviour. The complexity of the material also meant multiple crystal behaviours at once are often examined instead of each in isolation, which may result in invalid and inaccurate results.⁷ Moreover the partial levitation of the LK99 that was said to show the Meissner effect was more likely caused by ferromagnetism instead. Due to these alternative behavioural explanations many scientists have stopped investigating the LK-99 further.
This isn’t the first time claims of a room temperature superconducting material have made scientific headlines. In March, Ranga Dias, a professor of mechanical and chemical engineering, and his team at the University of Rochester had supposedly found a room temperature superconducting material and published their findings in the esteemed science journal Nature. The material largely consisted of lutetium with some hydrogen and nitrogen atoms mixed in it. Not long after, accusations of scientific misconduct, data manipulation and plagiarism arose, with one graduate student on the team saying “Our concerns largely were dismissed by Dr. Dias, and some of us were instructed by Dr. Dias not to probe further into the issues raised and/or not to worry about such concerns”.⁸ 8 of those 11 scientists have since asked Nature to retract the paper. Both of these cases show how even though there are many passionate and dedicated to finding a room temperature superconducting material, the path is long and difficult with many obstacles.
Superconductor stocks spiked greatly after the publishing of the LK99 paper, despite warnings from regulators and companies who advised against it. After no concrete progress was made in replicating the South Korean researchers findings, these stocks and other superconductor-related stocks plunged massively. Despite these controversies the stocks of the American Superconductor Corporation’s shares have still risen 10.7% since the end of July⁹ and research continues as many maintain hope for the future. The volatility of the superconductor stock markets after the LK-99 shows just how colossal and impactful a room-temperature superconductor would be to the global industry.
In conclusion, superconductors have and will continue to change the world with their amazing applications and potential to develop a variety of cutting-edge technologies like faster and more environmentally-friendly transport, quantum computers, electron microscopes, and particle accelerators. As research on superconductors continues to push the limits of possibility, who knows that room-temperature and low-pressure superconductors as a reality may not be that far off.
References:
CHINT Group Corp. (n.d.). How Much Power Loss in Transmission Lines. CHINT Global. https://chintglobal.com/blog/how-much-power-loss-in-transmission-lines/
Davis. (2022, September 9). How The First Superconducting Qubit Changed Quantum Computing Forever. Medium. Retrieved October 8, 2023, from https://medium.com/qiskit/how-the-first-superconducting-qubit-changed-quantum-computing-forever-96cf261b8498
Ryan, J. (2023). LK-99 Superconductor: From Breakthrough Hope to More Humble Reality. CNET. https://www.cnet.com/tech/computing/lk-99-superconductor-maybe-a-breakthrough-maybe-not-so-much/
Superconductor Pb10−xCux(PO4)6O showing levitation at room temperature and atmospheric pressure and mechanism. (2023, July 22). Cornell University. https://arxiv.org/abs/2307.12037
Jain, P. K. (2023, September 8). Superionic Phase Transition of Copper(I) Sulfide and Its Implication for Purported Superconductivity of LK-99. The Journal of Physical Chemistry C. https://doi.org/10.1021/acs.jpcc.3c05684
Cho, A. (2023). A spectacular superconductor claim is making news. Here’s why experts are doubtful. Science. https://www.science.org/content/article/spectacular-superconductor-claim-making-news-here-s-why-experts-are-doubtful
Kim, H. T. (2023). Hopes fade for ‘room temperature superconductor’ LK-99, but quantum zero-resistance research continues. The Conversation. https://theconversation.com/hopes-fade-for-room-temperature-superconductor-lk-99-but-quantum-zero-resistance-research-continues-211733
Chang, K. (2023, September 29). 11 Scientists Found a Room-Temperature Superconductor. Now 8 of Them Want a Retraction. The New York Times. https://www.nytimes.com/2023/09/29/science/superconductor-retraction-ranga-dias-rochester.html
Asplund, R. (n.d.). Are Superconductor Stocks the New Meme Stocks? Barchart. https://www.nasdaq.com/articles/are-superconductor-stocks-the-new-meme-stocks
Images:
Image showing a superconductor magnet plate and permanent magnet levitating. https://www.science.org/content/article/spectacular-superconductor-claim-making-news-here-s-why-experts-are-doubtful
Diagram showing how the Meissner effect works. https://samajho.com/upsc/what-is-superconductivity-and-where-can-it-be-applied/
Another diagram shows the Meissner effect, comparing a normal magnet to a superconducting one where the magnetic field waves go around the conductor. https://energyeducation.ca/encyclopedia/Superconductor
Image showing how superconducting magnets are used in Japanese Maglev trains and therefore running at very high speeds. https://www.youtube.com/watch?v=XjwF-STGtfE
Image showing a superconducting circuit used in quantum mechanics.
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