Quantum Locking
Introduction
Quantum locking, also known as flux pinning, is a phenomenon where a superconductor is 'locked' in space above a magnetic field. This effect is due to the properties of type-II superconductors, which allow magnetic fields to penetrate their surface and create vortices. These vortices result in the superconductor being 'trapped' in a state of equilibrium above the magnetic field, thus creating the effect of quantum locking.
Superconductivity
Superconductivity is a quantum mechanical phenomenon where certain materials exhibit zero electrical resistance and expulsion of magnetic fields when cooled below a certain temperature. This temperature is known as the critical temperature. Superconductors can be classified into two types: type-I and type-II. The quantum locking phenomenon is primarily associated with type-II superconductors.
Type-II Superconductors
Type-II superconductors differ from type-I in that they allow magnetic fields to penetrate their surface when the applied magnetic field is between the lower and upper critical fields. This penetration forms quantum vortices, which are essentially tubes of magnetic field lines. These vortices are 'pinned' in place within the superconductor, leading to the phenomenon of quantum locking or flux pinning.
Flux Pinning
Flux pinning is the process where these vortices are 'pinned' or 'locked' in place within the superconductor. This occurs due to imperfections or defects within the superconductor's crystal lattice structure. These defects provide locations where the vortices can become trapped, thus preventing them from moving. This pinning of the vortices is what leads to the superconductor being 'locked' in place above a magnetic field.
Quantum Locking in Practice
In practical applications, quantum locking can be observed through the levitation of a superconductor above a magnetic track. When the superconductor is cooled below its critical temperature and placed above a magnetic track, it will levitate at a fixed height. This height is determined by the density of the vortices within the superconductor. The superconductor can be moved along the track, but it will maintain its orientation and height due to the vortices being pinned in place.
Future Applications
The phenomenon of quantum locking has potential for various future applications. These include magnetic levitation trains, known as maglev trains, which could utilize this technology to achieve frictionless travel. Additionally, it could be used in energy storage systems, such as superconducting magnetic energy storage (SMES) systems, to improve efficiency and capacity.