Superconductivity Of Mercury

Description

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Context

Recently, Researchers from the University of L' Aquila Italy have found a comprehensive microscopic understanding of the super productivity of Mercury.

Mercury

Mercury is a heavy, silvery-white metal that is liquid at room temperature.
Compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity.
It has a freezing point of −38.83 °C and a boiling point of 356.73 °C, both the lowest of any stable metal.
It is found either as a native metal(rare) or in cinnabar, metacinnabar, sphalerite, corderoite, livingstonite, and other minerals, with cinnabar (HgS) being the most common ore.

Superconductivity

Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material.
In this, materials to conduct direct current (DC) electricity without energy loss when they are cooled below a critical temperature(referred to as T_c). These materials also expel magnetic fields as they transition to the superconducting state.
This capacity produces interesting and potentially useful effects. Superconductivity was first observed in 1911 by H. K. Onnes, a Dutch physicist.
Superconductors have been employed in, or proposed for use in, an enormous variety of applications. Examples include high-speed magnetic-levitation trains, magnetic-resonance-imaging (MRI) equipment, ultra-high-speed computer chips, high-capacity digital memory chips, alternative energy storage systems, radio-frequency (RF) filters, radio-frequency amplifiers, sensitive visible-light and infrared detectors, miniaturized wireless transmitting antennas, systems to detect submarines and underwater mines, and gyroscopes for earth-orbiting satellites.

Superconductivity of Mercury

In 1911, Dutch physicist Heike Kamerlingh Onnes discovered superconductivity in mercury. He found that at a very low temperature, called the threshold temperature, solid mercury offers no resistance to the flow of electric current.

The BCS theory

Scientists later classified mercury as a conventional superconductor because its superconductivity could be explained by the concepts of Bardeen-Cooper-Schrieffer (BCS) theory.

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BCS Theory

BCS Theory describes superconductivity as a microscopic effect caused by a condensation of Cooper pairs- a pair of electrons in a superconductor that is attractively bound and has equal and opposite momentum and spin. Below a specific critical temperature, the electrons in a metal pair up to create bosons called Cooper pairs. These Copper pairs can move like water in a stream, facing no resistance to their flow, below a threshold temperature.

While scientists have used the BCS theory to explain superconductivity in various materials, they have never fully understood how it operates in mercury — the oldest superconductor.
Now, recently, scientists have drawn a clear picture of how mercury becomes a superconductor.

Recent Research on Mechanism of Superconductivity in Mercury

When the researchers accounted for the relationship between an electron’s spin and momentum, they could explain why mercury has such a low threshold temperature (around –270°C).
The group found that one electron in each pair in mercury occupied a higher energy level than the other. This lowered the Coulomb repulsion (like charges repel) between them and nurtured superconductivity.
Thus, the group has explained how mercury becomes a superconductor below its threshold temperature.

Closing Thought

The findings suggest that we could have missed similar anomalous effects in other materials, leading to previously undiscovered ones that can be exploited for new and better real-world applications.

https://www.thehindu.com/sci-tech/science/a-clear-picture-of-how-mercury-becomes-a-superconductor/article66346400.ece