Superconductivity at Room Temperature

• 28 Oct 2020

Why in News

Recently, researchers have created a material that is superconducting at room temperature, however, it only works at a pressure of 267 Gigapascals (GPa), which is equivalent to about three-quarters of pressure at the centre of Earth (360 GPa).

Key Points

• Material Used: A mixture of carbon, hydrogen and sulfur was put in a microscopic niche carved between the tips of two diamonds (diamond anvil) and laser light was used on them to trigger chemical reactions.
• Process:
  
  • As the experimental temperature was lowered, resistance to a current passed through the material dropped to a vanishingly small value below the critical temperature (Tc).
  • The transition of the sample to become superconductive occurred the best at transition temperature of around 15°C at 267 GPa.
• Verification: To verify that this phase was indeed a superconductor, the group ascertained that the magnetic susceptibility of the superconductor was that of a diamagnet.
  
  • A superconducting material kept in a magnetic field expels the magnetic flux out its body when cooled below the critical temperature and exhibits perfect diamagnetism.
  • It is also called the Meissner effect which simply means that magnetic lines do not pass through superconductors in a magnetic field.
• Superconductors:
  
  • A superconductor is a material that can conduct electricity or transport electrons from one atom to another with no resistance.
  • No heat, sound or any other form of energy would be released from the material when it has reached critical temperature (Tc), or the temperature at which the material becomes superconductive.
    
    • The critical temperature for superconductors is the temperature at which the electrical resistivity of metal drops to zero.
  • Prominent examples include aluminium, niobium, magnesium diboride, etc.
• Applications:
  
  • From magnetic resonance imaging (MRI) machines, low-loss power lines, ultra powerful superconducting magnets to mobile-phone towers.
  • Researchers are also experimenting with them in high-performance generators for wind turbines.
• Limitations:
  
  • Their usefulness is still limited by the need for bulky cryogenics (production of and behavior of materials at very low temperatures) as the common superconductors work at atmospheric pressures, but only if they are kept very cold.
    
    • Even the most sophisticated ones like copper oxide-based ceramic materials work only below −140°C.
• Significance of the Research:
  
  • If researchers can stabilise the material at ambient pressure, applications of superconductivity at room temperatures could be achieved and will be within reach.
  • Superconductors that work at room temperature could have a big technological impact, for example in electronics that run faster without overheating.

Diamagnetism

• It 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 non-permanent 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.

Meissner Effect

• When a material makes the transition from the normal to the superconducting state, it actively excludes magnetic fields from its interior and 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.

Source: TH