What is Superconductivity and where can it be Applied?

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Context: New results from IIT Mandi indicate that nanostructures made of gold embedded with silver show zero resistance to the flow of electric current through them. About a year ago, two scientists from the Indian Institute of Science (IISc)-Bangalore reported an extraordinary finding on a public online scientific forum they had observed superconductivity at room temperature, in a new composite material made of gold and silver.

Relevance:
For Prelims: 
Science and Technology- Superconductivity
For Mains: GS III- Superconductors and their future uses

What is Superconductivity?
  • Superconductivity is a phenomenon that, so far, has been possible only at extremely low temperatures, in the range of 100°C below zero.
  • Superconductivity is a state in which a material shows absolutely zero electrical resistance.
  • Electricity is essentially the movement of free electrons in a conducting material like copper. While the movement of electrons is in one particular direction, it is random and haphazard.
  • They frequently collide with one another, and with other particles in the material, thus offering resistance to the flow of current.
  • In a superconducting state, however, the material offers no resistance at all. All the electrons align themselves in a particular direction and move without any obstruction in a “coherent” manner. It is akin to vehicles moving in an orderly fashion on a superhighway.
  • Because of zero resistance, superconducting materials can save huge amounts of energy, and be used to make highly efficient electrical appliances.
  • The problem is that superconductivity, ever since it was first discovered in 1911, has only been observed at very low temperatures, somewhere close to what is called absolute zero (0°K or -273.15°C).
  • Creating such extreme conditions of temperature and pressure is a difficult task. Therefore, the applications of superconducting materials have remained limited as of now.
What is Superconductor?
  • Superconductors are materials that conduct electricity with no resistance.
  • Unlike the more familiar conductors such as copper or steel, a superconductor can carry a current indefinitely without losing any energy.
  • Since its discovery in 1911 by Heike Kamerlingh Onnes, superconductivity has been an important area of research for physicists and engineers alike.
  • Starting with the discovery of mercury as superconducting material, the list of superconductors has grown to include more than just conductive metals, as many ceramics also exhibit superconducting properties.
  • Although many metals are conductive, not all conducting materials are superconductive, and even some insulators are able to become superconductive under the right conditions.
  • Superconductors have gained interest due to their ability to drop their resistivity to zero when the material is below a certain temperature.
  • One phenomenon that occurs in superconductors below the critical temperature is the Meissner effect, which is where a superconductor expels all magnetic field from within itself.
  • One of the most well-known demonstrations of the Meissner effect is its ability to make a magnet levitating above a superconductor
  • The disappearance of electrical resistivity was modelled in terms of electron pairing in the crystal lattice by John Bardeen, Leon Cooper, and Robert Schrieffer in what is commonly called the BCS theory (Bardeen–Cooper–Schrieffer theory is the first microscopic theory of superconductivity since Heike Kamerlingh Onnes's 1911 discovery).


Advantage of superconductors

  • Currently, superconductivity can only be achieved at temperatures far below zero, in processes that are too expensive for wider application.
  • The devices have low power dissipation, high operating speed, and extreme sensitivity.
  • Devices built with room temperature superconductors tend to be extremely efficient and entail large savings in both energy and costs.


What are its Applications?

  • Superconductors already have drastically changed the world of medicine with the advent of MRI machines, which have meant a reduction in exploratory surgery.
  • Power utilities, electronics companies, the military, transportation, and theoretical physics have all benefited strongly from the discovery of these materials.

Superconductors have the following applications:

  1. Maglev (magnetic levitation) trains- These work because a superconductor repels a magnetic field so a magnet will float above a superconductor– this virtually eliminates the friction between the train and the track.
    • Superconducting magnets have been used to levitate trains above its rails. They can be driven at high speed with minimal expenditure of energy.
    • However, there are safety concerns about the strong magnetic fields used as these could be a risk to human health.
  2. Large hadron collider or particle accelerator- This use of superconductors was developed at the Rutherford Appleton Laboratory in Oxfordshire, the UK in the 1960s.
    • The latest and biggest large hadron collider built in Switzerland by a coalition of scientific organisations from several countries. 
    • Superconductors are used to make extremely powerful electromagnets to accelerate charged particles very fast (to near the speed of light).
  3. SQUIDs (Superconducting Quantum Interference Devices) are used to detect even the weakest magnetic field. They are used in mine detection equipment to help in the removal of land mines.
  4. The USA is developing “E-bombs”- These are devices that make use of strong, superconductor-derived magnetic fields to create a fast, high-intensity electromagnetic pulse that can disable an enemy’s electronic equipment.
    • These devices were first used in wartime in March 2003 when USA forces attacked an Iraqi broadcast facility.
    • They can release two billion watts of energy at once. fast digital circuits (including those based on Josephson junctions and rapid single flux quantum technology),
  5. Powerful superconducting electromagnets used in magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) machines, magnetic confinement fusion reactors (e.g. tokamaks), and the beam-steering and focusing magnets used in particle accelerators.
  6. RF and microwave filters (e.g., for mobile phone base stations, as well as military ultra-sensitive/selective receivers)
  7. High sensitivity particle detectors, including the transition edge sensor, the superconducting bolometer, the superconducting tunnel junction detector, the kinetic inductance detector, and the superconducting nanowire single-photon detector.
  8. Superconductors are also used in high field scientific magnets.
  9. Superconducting magnetic propulsion systems may be used to launch satellites into orbits directly from the earth without the use of rockets.
  10. High-efficiency ore-separating machines may be built using superconducting magnets which can be used to separate tumour cells from healthy cells by high gradient magnetic separation method.
  11. Since the current in a superconducting wire can flow without any change in magnitude, it can be used for transmission lines.

The use of superconductors under development (future uses)- 

  1. Very fast computing
  2. low-loss power cables

Other impacts of superconductors on technology will depend on either finding superconductors that work at far higher temperatures than those known at present or finding cheaper ways of achieving the very cold temperatures currently needed to make them work.

Blue skies research:

  • Scientific research that does not have a particular commercial aim in view is called blue skies research.
  • Many discoveries are made ‘by chance’ when scientists are trying to find out something else.
  • The discovery of superconductivity was made nearly 100 years ago but technological applications have really only become available in the last 10 years or so.
Zero Resistance
  • The search for a material that exhibits superconductivity at room temperature, or at least manageable low temperatures, has been going on for decades, without success.
  • In a superconducting state, however, the material offers no resistance at all.
  • All the electrons align themselves in a particular direction and move without any obstruction in a “coherent” manner.
  • It is akin to vehicles moving in an orderly fashion on a superhighway.
  • Because of zero resistance, superconducting materials can save huge amounts of energy, and be used to make highly efficient electrical appliances.
Why is superconductivity difficult to achieve?
  • The problem is that superconductivity, ever since it was first discovered in 1911, has only been observed at very low temperatures, somewhere close to what is called absolute zero (0°K or -273.15°C).
  • The biggest application for superconductivity is in producing the large-volume, stable, and high-intensity magnetic fields required for MRI and NMR.
  • The magnets typically use low-temperature superconductors (LTS) because high-temperature superconductors are not yet cheap enough to cost-effectively deliver the high, stable, and large-volume fields required, notwithstanding the need to cool LTS instruments to liquid helium temperatures. 
  • In recent years, scientists have been able to find superconductive materials at temperatures that are higher than absolute zero.
  • But in most cases, these temperatures are still below -100°C and the pressures required are extreme.
  • Creating such extreme conditions of temperature and pressure is a difficult task.
  • Therefore, the applications of superconducting materials have remained limited as of now.
  • Fulfilling a decades-old quest, researchers from the University of Rochester, Intel Corporation and the University of Nevada recently reported creating the first superconductor that does not have to be cooled for its electrical resistance to vanish.
  • A compound of hydrogen, carbon and sulfur (hydrogen sulphide) has broken a symbolic barrier, it seems to conduct electricity without any resistance at temperatures of up to about 15 °C.
  • There’s a catch- the new room-temperature superconductor only works at a pressure equivalent to about three-quarters of that at the centre of Earth.
  • But if researchers can stabilize the material at ambient pressure, dreamed-of applications of superconductivity could be within reaches, such as low-loss power lines and ultrapowerful superconducting magnets that don’t need refrigeration, for MRI machines and maglev trains.
Way Forward
  • The IISc scientists have had reported that some of their samples of nanoparticles of gold-silver composite material displayed superconductivity at 13°C and under normal atmospheric pressure.
  • They have provided evidence of these samples displaying two fundamental properties of a superconductor- zero resistance to electrical current, and diamagnetism.
    • Diamagnetism is a property opposite to normal magnetism that we are used to.
    • A diamagnetic substance repels an external magnetic field, in sharp contrast to normal magnetism, or ferromagnetism, under which a substance is attracted by an external magnetic field.
  • If confirmed, this would probably be the biggest discovery to come out of an Indian laboratory since the Raman effect in the 1920s.
  • It would take more effort by the authors to convincingly show that the nanomaterial is indeed superconducting. The paper posted earlier had very little data.
  • Now, more data are available. Whether the data are correct or not can be settled only through scientific discourse, peer-reviewing and other groups reproducing it.


Additional Information:

  • Meissner effect: When a material makes the transition from the normal to the superconducting state, it actively excludes magnetic fields from its interior; this is called the Meissner effect. This constraint to zero magnetic fields inside a superconductor is distinct from the perfect diamagnetism which would arise from its zero electrical resistance.
  • Critical temperature: The critical temperature for superconductors is the temperature at which the electrical resistivity of metal drops to zero. The transition is so sudden and complete that it appears to be a transition to a different phase of matter; this superconducting phase is described by the BCS theory.
  • Diamagnetism: Diamagnetism is a very weak form of magnetism that is induced by a change in the orbital motion of electrons due to an applied magnetic field. This magnetism is nonpermanent and persists only in the presence of an external field. The magnitude of the induced magnetic moment is very small, and its direction is opposite to that of the applied field.



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