Explained: Superconductivity

• About a year ago, two scientists from IISc Bangalore had observed superconductivity at room temperature, in a new composite material made of gold and silver.
• If the claimed discovery is confirmed, it could be one of the biggest breakthroughs in physics in this century so far.

Silver embedded gold matrix

• The material that exhibited superconductivity is in the form of nanosized films and pellets made of silver nanoparticles embedded in a gold matrix.
• Interestingly, silver and gold independently do not exhibit superconductivity.

What is Superconductivity?

• 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.
• The picture is similar to one of messy traffic in a congested urban area. In the process, a lot of electrical energy is lost as heat. Resistance is a measurable quantity, which varies with the material.
• Superconductivity is a state in which a material shows absolutely zero electrical resistance.
• While resistance is a property that restricts the flow of electricity, superconductivity allows unhindered flow.
• It is a phenomenon that, so far, has been possible only at extremely low temperatures, in the range of 100°C below zero.

A phenomenon of 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).
• 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.