Superconductors have zero electrical resistance. Image credit: morguefile.com
A research team from Washington State University has found superconductivity in a compound that seems to oppose conventional understanding of the phenomenon.
Superconductivity is an intriguing characteristic which a select few materials possess, which essentially means the material (or ‘superconductor’) has zero electrical resistance and expels any external magnetic field. This phenomenon is revealed once a material is cooled below a specific temperature, known as the superconducting transition temperature or critical temperature.
It is currently an important property in producing highly electrically efficient technology, such as MRI machines with high-mobility, quieter magnetic trains and fault current limiters and transformers with improved energy quality.
The below video shows an interesting practical application of superconductivity, magnetic levitation for use in magnetic trains.
The most famous of the high temperature superconductors, that is superconductors with a transition temperature above 77K, are the YBCO family, which are yttrium-barium-copper oxides. These were the first group of materials to demonstrate superconductivity above the boiling point of liquid nitrogen, making them easier to use in practical applications than previous superconductors.
To read more about pioneering work on high temperature superconductors, click here for an insightful interview with Professor Paul Chu, one of the most important names in superconductivity research.
Very disordered state
However, the new discovery seems to go against conventional superconductivity wisdom.
The Washington team observed superconductive properties in solid carbon disulphide, which is more commonly found in it liquid form as an insecticide or chemical solvent. The compound started to display superconductive properties at a temperature of 6.2K, and at pressures in the range of 50 to 172 gigapascals.
Commenting on the discovery in a recent press release, research team leader Choong-Shik Yoo said:
"What makes this discovery special is that it seems counter to the understanding of how superconductivity normally works."
The reason that the superconductive properties are surprising is that predominantly superconductivity is found in highly ordered molecular structures. However, in the case of carbon disulphide, the compound displays superconductive properties in a very disordered state. This is not completely unheard of, but is certainly a rarity and could lead to a greater understanding of superconductivity. Still more surprising to the research team was the fact that prior to this disordered state, the compound displayed a magnetically ordered state before structurally altering at the point of superconductivity.
Carnegie’s Viktor Struzhkin explains the importance of the findings, which have recently been published by the Proceedings of the National Academy of Sciences:
"These results show the interplay between superconductivity, magnetism and structural disorder." "We are already at work searching for other highly conducting states in similar molecular systems in close collaboration with Professor Choong-Shik Yoo's team."
Original source: Carnegie Institution