New images of iron-based superconductors are providing telltale clues to the origin of superconductivity in a class of ceramic materials known as pnictides. The images reveal that electrons responsible for the superconducting currents in some pnictides tend to flow primarily along the boundaries between the crystal grains that make up the superconductors. The research, which is reported in a pair of papers appearing in the current issue of the journal Physical Review B , may help physicists to find new superconducting compounds that can carry current without the electrical resistance that plagues conventional metal conductors. In order to identify the stripes that represent regions with dense superconducting currents, a group of Stanford University researchers measured the depth that magnetic fields penetrated into a superconducting sample.
Superconductivity and Microwaves
Critical magnetic fields for superconductors
Superconductivity conforms to a quantum, thermal, and electrodynamic set of physical phenomena of great interest by themselves. They have, also, the potential to be one clean energy source that technology is looking for. Superconductors do not allow static magnetic fields to penetrate them below a critical field, that is, Meissner effect. However, microwave magnetic fields do penetrate them already, and their energy is readily absorbed by the superconductor. High-temperature, perovskite superconductors do absorb microwave energy the most due to the presence of unpaired electron spins, fluxoid dynamics, and quasiparticle motion.
Stripes offer clues to superconductivity
Below a certain temperature, materials enter a superconducting state and offer no resistance to the passage of electrical current. In , while studying the properties of matter at very low temperature, the Dutch physicist Heike Kamerlingh Onnes and his team discovered that the electrical resistance of mercury goes to zero below 4. This was the very first observation of the phenomenon of superconductivity. The majority of chemical elements become superconducting at sufficiently low temperature.