A Superconductor is a superior conductor whose resistance attains a zero resistance after reaching a specific temperature and hence provide nearly a 100% of efficiency in transmission of electricity. This amazing property of a conducting substance allows current to flow smoothly without any energy loss. Thus, it has become a fascinating discovery in various fields of science and technology. The first discovery of superconductors was made by a Dutch physicist, Heike Kamerlingh Onnes and ever since it has become a topmost demand of today’s technological era.
What are Superconductors?
A superconducting material has an ability to conduct electricity without the loss of any forms of energy, when the material is colder than a critical temperature. Thus, to attain superconductivity the material must be at an extraordinarily low temperature state. An excessive energy amount is required to reach that state of a material which turns out to be very costly and a vast process. However, research is being carried on to gain the superconducting state of different materials. Aluminium, magnesium diboride, niobium, copper oxide, yttrium barium and iron pnictides are the famous superconductors at present.
A critical temperature is a point at which the resistivity of a material becomes zero and beyond which the material gains its superconducting state. At low temperatures, the majority of materials experience superconducting phase transitions. Before 1986, the highest critical temperature was roughly 23 K. In 2020 a latest discovery was made where a super-conductor was found at a room-temperature which was made up of carbon, hydrogen and sulfur. The underlying pressure was about 270 gigapascals and possessed a highest temperature of superconductivity. Superconductors also expel magnetic fields from the surface during phase transition, called the meissner effect. Hence, these two properties like zero resistance and not permitting magnetic field make superconductors a way superior to traditional conductors like copper and silver.
How do Superconductors Work?
Superconductivity is a very complex state to achieve. When the temperature of a metal goes below critical temperature, the electrons in the metal form a bond. As these electrons are fermions, they are bound to create bosons below the critical temperature. This bond of two electrons directed opposite to each other is called cooper pairs. This happens at incredibly low temperatures. When the metal gets heated this cooper pair bond tends to break and electrical resistance comes forward.
According to the BCS Theory(Bardeen–Cooper–Schrieffer theory), Cooper Pairs move through the lattice without showing any dispersion. This prevents electrical resistance through the metal. Due to lattice vibrations called phonons, the pairing of entangled electrons is made possible. It has been observed that some metals become superconducting at higher temperatures. The physics behind it is quite vague. However it is believed that higher-level electron interactions probably occur rather than a simple case of cooper pairs.
Types of Superconductors: Low-Temperature vs. High-Temperature
Depending upon the critical temperatures, superconductors are divided into two types:
- Low-Temperature Superconductors
- They have very low critical temperatures and exist about absolute zero (below 30 K, or -243.15°C).
- They are used in MRI machines, particle accelerators, and scientific research Example, niobium-titanium (NbTi) and lead (Pb)..
- High-Temperature Superconductors
- These have very high critical temperatures and can operate above 77 K(-196.15°C)
- Generally liquid nitrogen is used to cool them in place of costly helium.
- They are used in power grids, maglev trains, and energy-efficient electronics. For example, yttrium barium copper oxide (YBCO) and bismuth strontium calcium copper oxide (BSCCO).
Real-World Uses of Superconductors
In every sector of science like physics, engineering and medicine, superconductors are widely used. Some of its uses are given below:
- Superconducting Cables
Superconducting cables are used in power transmissions to reduce the energy loss and get maximum power transfer. Normal cables like aluminium and copper will give a high amount of power loss. So to overcome this defect and get 100% transmission, these cables are used. However it is a very expensive method and only few companies are affording it commercially.
- Magnetic Resonance Imaging (MRI)
Doctors use superconductors to produce clear imaging of internal organs in MRI machines. As magnetic fields float through the surface of the superconductor, a powerful field is generated. High power electromagnets are used to produce these magnetic fields. In addition, superconductors resist any disturbances and hence no heat is produced. Thus, electromagnets produce the required magnetic field.
- Maglev Trains
Maglev trains highly rely on electromagnetic induction. They float above the track due to superconducting magnets. These magnets extremely reduce friction and give high speeds to the train.
- Particle Accelerators
Superconducting electromagnets are used in particle accelerators like the Large-Hadron Collider. Electric power without any resistance and high amount of magnetic field will allow subatomic particles to accelerate at very high speeds (nearly equal to the speed of light).
- Quantum Computing
Quantum computing is made possible because of superconductors. Superconducting materials are used to develop qubits and other basic units which allows an exceptional computing capacity of quantum computers.
- Power Grids and Energy Storage
By transmitting electricity with nearly zero losses, superconducting power cables improve the efficiency of the power grid and lowers energy waste.
Beside these, several technologies like railguns, coilguns, cell phone base stations, fast digital circuits and nuclear reactors rely on superconductors.
The Benefits of Using Superconductors
Superconductors are superior to normal conductors because of their unique features. Some of them are given below:
- Zero Energy Loss: The main benefit is that it provides nearly 100% of energy transmission which becomes possible due to zero electrical resistances. This also reduces the possible loss of energy.
- Stronger Magnetic Fields: Superconductors also resists magnetic field and make it remain on the surface. Thus stronger magnetic fields are developed by superconductors.
- High-Speed Transportation: Maglev trains are made possible due to superconductors. Thus a super high speed with greater efficiency is achieved.
- Introduction of new Computing system: Quantum computing has taken the computing system to the next level and made our computing super fast.
- Improved Energy Storage: Superconductors allow to create better energy distribution and storage systems.
The History of Superconductors: Key Discoveries
Physicists studied for many years to create such a type of material which could provide maximum output in energy transmission. After a decade of research, it was found that the material could be built under certain specific conditions of temperatures and the theory of superconductivity emerged. In 1911, Heike Kamerlingh Onnes first discovered superconductivity by studying the behavior of mercury at temperature below 4.2 kelvin. He found that mercury exhibits zero resistance below that temperature. In 1913, he received a Nobel prize for the discovery. Later, superconductivity was found for various other materials such as for lead at 7 K and for niobium at 10 K.
In 1933, Walter Meissner and Robert Ochsenfeld discovered that superconductors don’t allow magnetic fields to pass inside them which is called the Meissner Effect. Similarly, in 1957, John Bardeen, Leon Cooper, and Robert Schrieffer gave a complete physics of superconductivity which was called the BCS Theory. It explained how cooper pairs flow in the metal lattice.
Lev Shubnikov discovered a new form of superconductor in 1937, which was intermediate of the normal and superconducting metals. In 1986, Karl Müller and Johannes Bednorz were awarded the Nobel Prize for developing a high-temperature superconductor for the first time using lanthanum-barium copper oxide (LBCO).
Lev Landau and Vitaly Ginzburg gave a hypothesis called the Ginzburg–Landau theory on superconductivity in 1950. They compared their theory of second-order phase transition with Schrödinger’s wave equation to explain the macroscopic properties of superconductors. Later, after the demise of Landau, Alexei Abrikosov discovered that Ginzburg–Landau theory indicates the two types of superconductors called type I and type II superconductors. This led them to a Nobel prize in Physics in 2003.
Scientists are now searching for superconductors that operate on room-temperatures. This could be a revolutionary discovery in Physics.
Challenges in Using Superconductors Today
Due to strict requirements to achieve the state, there are certain challenges faced while using superconductors. Some of the challenges are written below.
- Most superconductors need extremely low temperature to function, which could be impracticable for daily use.
- Superconductors are highly expensive and the cooling process is also very costly. Thus, it cannot be afforded by local groups.
- High-temperature superconductors are difficult to produce and use into certain applications due to their harsh nature.
- The mechanism to reach high-temperature superconductors lacks clarity.
- It is a very complex process and requires a knee-deep study of the theory.
The Future of Superconductors: What’s Next?
To minimize the current defaults and bring improvements in the implementations, certain concepts are being developed under superconductors.
- Room-Temperature Superconductors
The main goal of solid-state physicists today is to produce superconductors which operate locally. This can be a milestone in physics and could be employed in daily appliances at affordable prices. In 2020, scientists detected superconductivity at 15°C but under extreme pressures. Attaining superconductivity at ordinary conditions would drastically change the real-world applications of superconductors.
- Advanced Materials
Researchers are also testing new materials that need less effort of cooling and are durable.
- Improved Manufacturing Process
Implying cheap manufacturing processes will make superconductors easier to obtain for business purposes.
- Replacement of Electronics
The use of superconducting devices in the future like super-transistors and super-circuits could give a highly efficient computing system with very less amount of heat generated.
Conclusion
Superconductor is one of the powerful discoveries in solid-state and condensed matter physics. It has wide implications in engineering, medical sectors and quantum mechanics. A super-fast computing system and transport is made possible by this technology. It would be wonderful if the discoveries were possible in normal conditions. But till date it has remained challenging to employ it locally due to the tough requirements to meet the critical temperature and to develop incredibly low cooling systems.
Research is being carried out to make everything simpler. In future generations’ science could reach its peak by the development of room-temperature superconductors. The combination of those superconductors and quantum mechanics could probably provide a new taste of technology. (Also read about semiconductors)
References
Narlikar, A. V. (2014). Superconductors. Oxford University Press.
Schmidt, V. V. E. (2013). The physics of superconductors: Introduction to fundamentals and applications. Springer Science & Business Media.
Huse, D. A., Fisher, M. P., & Fisher, D. S. (1992). Are superconductors really superconducting?. Nature, 358(6387), 553-559.
Ford, P. J., & Saunders, G. A. (2004). The rise of the superconductors. CRC press.
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