What is a superconductor?
Electricity powers much of the modern world, providing an efficient way to move energy. How to make this process as efficient as possible? Quantum mechanics has the answer: use a superconductor. The superconductor is a special phase of matter able to conduct electricity with essentially zero losses. Kind of like a perpetual motion machine… only superconductors are real-life manifestations of the amazing - but often hidden - quantum world that we live in.
So exactly how is this miracle of nature achieved? It turns out that the rules of quantum mechanics are very strictly obeyed, in fact in more than a century of exploration, there has never been any evidence of quantum mechanics being incomplete. These strict rules govern the way particles play together, and depend on the kind of particles involved.
The carriers of electrical current are electrons. These quantum particles are from a group known as Fermions. In the quantum world, Fermions are perfectly anti-social: two identical Fermions are never found in the same quantum state. However, under special circumstances, identical Fermions can pair up into a new “quasi-particle” called a Cooper pair. Cooper pairs can still carry electrical current, but with an important difference - they are from a different quantum group known as Bosons. Bosons are the opposite of Fermions in that they are perfectly social: two identical Bosons want to be in the same quantum state!
The rules of quantum mechanics are so strict that very cold electrons can be forced to make Cooper pairs, and these new quantum particles then collapse into a collective quantum state of motion that carries the electrical current with essentially zero resistance. Used to make powerful electromagnets for medical diagnostics (MRI) and in giant particle accelerators such as the Large Hadron Collider, superconductors are another incredible example of quantum mechanics writ large in the 21st Century. To find out more, check out the superconductor research group of Philip Brydon, here at Otago.
The Centre for Quantum Science is a University of Otago Research Centre hosted by the Department of Physics.
ashton.bradley [at] otago.ac.nz
niels.kjaergaard [at] otago.ac.nz