Superconductors – How is Electricity Conducted With no Resistance

Superconductors may seem like perfectly ordinary materials, but turn down the thermostat and their superpowers are revealed…

Superconductors are metals (such as lead) or oxides which conduct electricity with no resistance. There’s just one catch – to display their superpowers, they need to be kept at a frosty -260 or so degrees Celsius (-436 degrees Fahrenheit).

Peer inside a chunk of lead and you’ll see row upon row of neatly packed ions, bathed in a swarm of electrons. These loose electrons are what conduct electricity – set them into motion and you have an electrical current. At room temperature, the lead ions vibrate away frenetically.

From an electron’s perspective, it’s like trying to negotiate a crowded dance floor without spilling your drink. Constant collisions between electrons and ions convert electrical energy into heat; this is resistance.

Turn the temperature down a few hundred notches though and the ion vibrations subside, creating a stable lattice. Now, as electrons flow through, a new effect comes into play: distortions in the lattice force them into pairs. These unlikely unions trigger a weird quantum physics quirk: electron pairs throughout the material coalesce into a perfectly synchronised cloud, moving a bit like a school of fish. This means that the swarm of electrons can move through the lattice with no collisions, resulting in no resistance.

Thanks to this astounding property, a huge current can be run through a superconductor without it overheating. This means they can create incomparably powerful electromagnets. These are currently used in MRI scanners, supercomputers, particle accelerators (like the LHC) and levitating maglev trains.

The potential of superconductivity

Despite their impressive abilities, most current superconductor technologies remain chained to hi-tech science laboratories, burdened by bulky, energy-greedy and very expensive cooling systems in order to function.

Scientists have, however, set their sights on creating a superconductor that works at room temperature, which could bring cutting-edge technologies into all of our day-to-day lives. Inexpensive, portable MRI scanners could drastically improve healthcare, while superfast maglev trains wouId zip up and down the country, considerably reducing travel times.

Replacing our inefficient electrical grids with superconducting cables would slash our electricity bills. It could also give renewable energies – such as wind farms – which are often located great distances from our cities a much deserved boost. Elsewhere, superconductor-enabled electronics could see smaller, faster computers hit the high street in the future.

While physicists have created superconducting materials operational at temperatures up to a ‘balmy’ -138 degrees Celsius (-211 degrees Fahrenheit), the mechanism behind these is not yet understood. Many still believe that the Holy Grail of room temperature superconductors is achievable – it’s just a matter of time and patience before we discover it.

Superconductor evolution

Take a journey through the last century to see just how far superconductors have come…

1911 – Absolute zero – Dutch physicist Kamerlingh Onnes (right) and a student create temperatures just below absolute zero and uncover that mercury is a good superconductor.

1933 – Levitation – Meissner and Ochsenfeld discover the Meissner effect: the uncanny ability of superconductors to repel magnetic fields and cause magnets to levitate.

1935 – Brothers London – Fritz and Heinz London reconcile superconductor theory to show that zero resistance and the Meissner effect stem from the same phenomenon.

1957 – BCS – Bardeen, Cooper and Schrieffer propose the BCS theory of superconductivity, explaining electron pairing. It earns them a Nobel prize.

1986 –  Hot stuff – Bednorz and Muller discover the first ‘high-temperature’ superconductor, which works its magic up to -243″C.

2009 – Hotter stuff – Today’s superconductivity temperature record is set by mercury barium calcium copper oxide, which acts as a superconductor up to a ‘blistering’-138″C.