26 Nov

Superconductivity

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Contents

• At what temperature superconductivity is achieved
• Applications of Superconductivity
• Superconductivity at Room Temperature?

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Definition

• Some materials when they are cooled below certain temperatures (Tcritical), they lose all electrical resistivity. This is called superconductivity.
  • It is one of the nature’s most intriguing quantum phenomenon and was first discovered more than 100 years ago in mercury cooled to temperature of liquid helium (-270 degree C) by Heike Kamerlingh-Onnes in 1911. He received 1913 physics Nobel Prize.

­ At what temperature superconductivity is achieved:

• The first material to have been discovered to show superconductivity was mercury. Most of the other materials commonly used as superconductors – Lead, Aluminium, Tin, Niobium, and several others also become superconducting at comparable temperatures, called Critical temperature.
• In some cases, superconductivity is achieved at slightly higher temperature but that is under increased pressure conditions.
• Even the materials that are classified as ‘high temperature superconductors’, as of now, show superconductivity properties only well below -150 degree C.
• The temperature at which the metals change from normal conducting state to superconducting state is called Critical/Transition temperature.
  • For e.g. below 4 degree Kelvin the metal mercury becomes a superconductor, therefore critical temperature for mercury is 4 K.
• The transition from normal conducting stage to superconducting stage is reversible.
• The super conducting material shows some extra ordinary properties which make them very important for modern technology. The research is still going on to understand and utilize these extraordinary properties of superconductors in various fields of technology.
  • Infinite conductivity (zero electric resistance)
    • Persistent current
  • Meissner Effect: a superconductor, expel the magnetic field and doesn’t allow the magnetic field to penetrate inside it. This phenomenon in superconductors is called Meissner effect.
  • Critical temperature
  • Critical magnetic field
  • Critical Current

Applications of Superconductivity

• Medical Sector: Used in magnetic resonance imaging, Magnetic Source imaging etc.
• Electric Engineering: For generation of high performing generators, motors, transformers, relays, superconducting magnets etc.
• Electronics: Quantum Computing, high quality sensors, filters, circuitry radar etc.
• Transportation: Magnetically levitated trains, Marine propulsion motors etc.
• Fundamental Physics: Particle accelerators, Magnets, Plasma / fusion research etc.

 Superconductivity at Room Temperature?

• The holy grail of superconductivity today is to find or create materials that can transfer energy between each other in a non-pressurized container.
  • If an efficient superconductor becomes possible at room temperature, it would revolutionize power transmission system for industry, commerce, and transportation.
• Several Wrong Claims and Skepticism: In recent years several claims of achieving superconductivity at room temperature has been found to be wrong. This has made scientific community a bit skeptic about any such new claim.
  • For e.g. in July 2023 only a research paper published in Physical Review Letters in 2021, by a US-based researcher making a similar claim had to be retracted.
  • Scientists at IISc Bengaluru had made similar claims in 2018, only to be sent for more reviews. The case is still unresolved.
• In July 2023, the South Korean researchers have posted two related papers on internet, not yet peer reviewed, claiming that a lead-based compound that they had developed had shown superconducting properties at room temperature, under normal pressure conditions. They are calling this material to be LK-99.

 Conclusion

Superconductivity at room temperature and room pressure if achieved could revolutionize a number of sectors including energy, transportation, health etc. This remains a holy grail yet to be
achieved.