Time to Turn Super

The word “super” describes something that surpasses human expectations and is unheard of or unimaginable. That is the kind of thing that happened in 1911 when a Dutch physicist by the name Heike Kammerlingh Onnes discovered something that left him awestruck .Onnes’ discovery was one of the greatest breakthrough made in scientific history. In his experiment Onnes had brought down a Mercury wires temperature to nearly absolute zero while passing a steady current and observed that the Mercury seized to show any sort of resistance. Baffled by this astonishing new discovery, Onnes is recalled saying, "Mercury has passed into a new state, which on account of its extraordinary electrical properties may be called the superconductive state". Yup I know, may be not the coolest way to announce the finding of superconductivity but none the less a great one, that opened the doors into the realm of possibilities. Besides this Onnes also conducted another amazing experiment where he passed current through a loop of lead wire at 4 Kelvin and a year later found that the current was still flowing with out significant loss.

The mesmerizing works of Superconductors might be known to a lot of people but not very much is known about the enigmatic phenomenon encompassing superconductive behavior. A basic definition for superconductive behavior would be that it’s a phenomenon observed in metals and ceramics (inorganic non metallic material which are formed by the action of heat) when they are cooled to near absolute zero temperature. Today however this definition is changing with the discovery of superconductors of Fullerene that exist in molecular level when 60 carbon atoms join to form a closed sphere and are doped with alkali metals.

It was not before long that the science world was trying to explain Onnes super discovery. In 1933 however Walther Meissner and R. Ochsenfeld made another breakthrough discovery. They saw that superconductors are not only perfect conductors
but also had the property to exclude a magnetic field. What it meant was that a superconductor will not allow magnetic field to pass through its interior. This interesting phenomenon occurs because the superconductor it self produces a current which in turn produces a field that just about balances the field outside. The Meissner effect is the main cause behind magnetic levitation.

Later in 1957 three physicists of Illinois University John Bardeen, Leon Cooper, and Robert Schrieffer presented the world with their BCS theory (after their last names). BCS theory suggests that as electrons pass trough the crystal lattice it gets deformed inwards as a result of which packets of sound called phonons are produced.





These phonons create a trough of positive charge at the areas of deformation as result assisting the movement of the following electrons in a process known as phonon mediated coupling and these couples of electrons are called ‘Cooper pairs’. The BCS theory was to be followed by yet another astounding break through. Brian Josephson a graduate student at Cambridge University predicted that two superconductors could conduct electricity even if there is an insulator between them. His predictions were later confirmed and the tunneling phenomenon is today known as the ‘‘Josephson Effect’’. These discoveries were subsequently followed by the prediction of organic superconductors and later their synthesis. But what happened in 1986 was probably one of the most crucial turning points in superconductor history. Alex Müller and Georg Bednorz , researchers at the IBM Research Laboratory in Rüschlikon, Switzerland, created a brittle ceramic compound that superconducted at the highest temperature then known: 30 K. Thus superconducting was no more tied to the feet by restrictions of temperature. Scientists began to test with what ever they found and cooked up any new recipes that they thought could be a superconductor at higher temperatures. Thus today the world record for the Superconductor with highest transition temperature (Tc) is held by a thallium-doped, mercuric-cuprate comprised of the elements Mercury, Thallium, Barium, Calcium, Copper and Oxygen. The Tc of this ceramic superconductor was confirmed by Dr. Ron Goldfarb at the National Institute of Standards and Technology-Colorado in February of 1994. Under extreme pressure its Tc can be coaxed up even higher - approximately 25 to 30 degrees more at 300,000 atmospheres.
The vast arrays of features make superconductors engineering marvels. Superconductors are being used in many different fields these days form medicine to space programs. Magnetic-levitation is an application where superconductors perform extremely well.

Transport vehicles such as trains can be made to "float" on strong superconducting magnets, virtually eliminating friction between the train and its tracks. The first of its kind the Yamanashi MLX01 maglev train opened on April 3, 1997. In December 2003, the MLX01 test vehicle attained an incredible speed of 361 mph (581 kph).

Who knew that the superconductors could also be life savers?

The field of Biomagnetism gives these babies a chance to show their magnetic life saving skills. The field generated by a superconductor is used in MRI (Magnetic Resonance Imaging).The super conducting field excites hydrogen atoms present in water and fat molecules of the body. They then release this energy at frequency that is detected by a computer and thus an image is created. A Korean group has taken Biomagnetism a step further by developing a device called the SQUID (Superconducting Quantum Interference Device). The SQUID makes use of the “Josephson Effect” and can detect changes in magnetic field over a billion times weaker than the force that moves the needle on a compass.

The uses of superconductors don’t just stop there; superconductors could be big money savers in the field of electricity too. Electric generators made with superconducting wire are far more efficient than conventional generators wound with copper wire. In fact, their efficiency is above 99% and their size about half that of conventional generators.

So how about it isn’t superconducting one of the greatest gifts of all from God to us humans. The best part is that currently as you read this some scientist somewhere might be finding out some thing absolutely new about the magnificent superconductors.
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By Tahsin Uddin Mullick
North South University, Dhaka, Bangladesh
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The Aftermath Publications, Issue 1
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