Superconductors may sound like something from science fiction, but don’t be fooled by their exotic-sounding name. In fact, they are already part of our everyday world. Every time a patient has an MRI scan in a hospital, superconducting magnets are involved. They are also crucial in large research facilities such as CERN, where they are used to guide and accelerate particles inside the Large Hadron Collider. Without superconductors, discoveries such as the Higgs boson would not have been possible. But what exactly is a superconductor, and why is it so special? This extraordinary phenomenon was first observed in 1911 by Dutch physicist Heike Kamerlingh Onnes, who discovered that mercury loses all electrical resistance at extremely low temperatures. It is precisely this absence of resistance, although not its only defining feature, that characterizes a superconductor.
A superconductor is a material that, when cooled below a certain temperature known as the critical temperature, can carry electricity with zero electrical resistance. In normal conductors such as copper, charge carriers (electrons) are constantly scattered by the vibrating crystal lattice, as well as by impurities and structural defects in the material. This scattering leads to energy loss and gives rise to electrical resistance. In a superconductor, however, these scattering events do not occur. As a result, there is no resistance and no energy loss.
A useful way to visualize this difference is to imagine the Tokyo metro during rush hour. In a conventional conductor, electrons are like passengers trying to enter a packed train, constantly colliding with others, struggling to move forward, and losing energy in the process. In a superconductor, however, the “train is empty.” Once the material is cooled below its critical temperature, the electrons enter what is known as a collective quantum state, and new charge carriers called Cooper pairs are formed. These Cooper pairs can move without scattering off obstacles in the material, as if they were travelling through a completely empty carriage. The properties of this collective quantum state are particularly useful for the creation and operation of qubits, which makes superconductors one of the leading candidate technologies for building quantum computers. In fact, companies such as Google and IBM already use superconductors in their quantum computers, and IBM has even begun to commercialize them.
The fact that current flows without resistance, and therefore without energy loss, does not mean that an infinite current can be transported; there are still physical limits. Nevertheless, superconductors can typically carry between 1000 and 10000 times more current than conventional copper conductors. The drawback is that superconductors have very low critical temperatures, usually below −170 °C. This means they must be continuously cooled using liquid nitrogen, hydrogen, or helium, which introduces technological challenges. Fortunately, cryogenics is now a highly developed field, and cooling is generally not a limiting factor for most applications.
As we can imagine, the fact that superconductors can carry electrical current without energy loss opens the door to a much more efficient way of distributing electricity. In fact, this advantage is already being exploited, and there are already superconducting cables installed and in operation. But the potential applications of superconductors do not end here. According to the laws of electromagnetism, which Maxwell unified in the second half of the 19th century, electric and magnetic fields are closely related. In fact, we can think of them as two sides of the same coin. This means that, without going into details, an electric current generates a magnetic field, and vice versa. Because superconductors can carry electric current without losses, they can also produce extremely strong magnetic fields. This is why they are already essential in MRI scanners and particle accelerators. Looking ahead, however, their potential becomes even more impressive.
In medicine, next-generation MRI systems based on stronger superconducting magnets could produce much higher-resolution images, allowing researchers to study diseases at the level of proteins and even viruses. Another area of application is the development of superconducting electrical machines that could be far more efficient and significantly lighter than conventional designs. For example, wind turbines could in principle achieve the same performance as current models while weighing roughly half as much. In transportation, superconductors could enable lighter and more efficient electric motors, particularly in aviation, where weight is critical. They are also the key technology behind Maglev trains, which float above the tracks using magnetic fields and can reach very high speeds with minimal friction.
Future particle accelerators in major high-energy physics laboratories also depend on superconductors. The magnets used in these accelerators accelerate particles to increasingly higher speeds. The faster the particles move, the more energetic their collisions become, and therefore the greater the chances of detecting new elementary particles. The next generation of accelerators will include magnets made from advanced superconducting materials, helping us uncover even deeper secrets of the universe. But accelerators are not used only to generate knowledge. They also play a key role in modern cancer treatments such as hadron therapy, where specific particles are accelerated and directed at tumors. This therapy is highly precise and produces very few side effects, since the particles release most of their energy directly in the tumor while passing through healthy tissue with minimal impact.
Superconductors may also play an essential role in future space exploration. One concept under development is the use of superconducting magnetic shields to protect astronauts spaceships electronics from cosmic radiation during long-duration missions, such as future journeys to Mars.
Perhaps the most transformative application is nuclear fusion. Nuclear fusion involves fusing hydrogen atoms in a reactor. In essence, this requires recreating the conditions of the Sun on Earth. The energy of the Sun and other stars comes from nuclear fusion occurring in their cores. The conditions required for this reaction are extreme. Temperatures of around 15 million degrees are needed together with pressures of about 250 million atmospheres. For reference, atmospheric pressure at sea level is 1 atmosphere. Obviously, reproducing these conditions on Earth is not easy, but superconductors make it possible. In practice, plasma, which is a gas of electrically charged particles, is heated to around 150 million degrees (larger temperatures than in the Sun because we can not achieve such larger pressures here). Clearly, anything that comes into contact with this plasma would be instantly vaporized, so it must be kept away from any material container. This is where superconductors play a crucial role. They generate extremely strong magnetic fields capable of confining the plasma so that it never touches the reactor walls. These magnetic fields can only be achieved using superconductors. This means that, without superconductors, controlled fusion energy would not be feasible.
Although often invisible to the public, superconductors are already embedded in modern technology, and their importance is expected to grow. In many ways, they are quietly becoming one of the key enabling technologies of the 21st century. It seems that the future may literally be superconducting.
Pablo Cayado received his Physics degree from the University of Oviedo in 2011. He
completed his PhD in Materials Science at the Institute of Materials Science of
Barcelona (ICMAB-CSIC) in 2016, with a doctoral thesis on superconductivity, a field
in which he has more than 15 years of experience and in which he continues to work to
this day.
After his PhD, he carried out postdoctoral research at the Karlsruhe Institute of
Technology (KIT) from 2016 to 2020, and subsequently at the University of Geneva
(UNIGE) until the end of 2024.
In early 2025, he returned to the University of Oviedo, where he is currently a Ramón y
Cajal fellow, lecturer, and established researcher.
He is also the founder and president of the scientific outreach association “Villaviciosa
ConCiencia”.