Rigid levitation and suspension of high-temperature superconductors by magnets

Abstract

A high-Tc superconductor floating freely above a magnet of low symmetry remains rigidly suspended in the air in almost any position and orientation as if stuck in an invisible heap of sand. This striking effect is due to pinning of the magnetic flux lines inside the superconductor and is often overlooked, since usually magnets with rotational symmetry are used for levitation. Magnets with rotational symmetry allow for nearly undamped orbiting and rotation of the superconductor about the magnet’s symmetry axis. But even in this geometry, flux-line pinning can be seen, since it forces the orbiting superconductor to turn the same face toward the axis. Superconductors with sufficiently strong pinning may even be suspended below a magnet.