Sometimes called the fifth state of matter, behind the more commonly known solids, liquids, gases and plasmas, Bose-Einstein condensates are what happens when you cool a gas of bosons right down to almost the coldest temperature possible. Experiments have shown that at this point, quantum phenomena can be observed at the macro scale. Scientists have used BECs as a starting point to create exotic states of matter like supersolids, excitonium, quantum ball lightning, and fluids exhibiting negative mass.
"A BEC is a unique state of matter as it is not made from particles, but rather waves", says Kozo Okazaki, lead author of the study.
"As they cool down to near absolute zero, the atoms of certain materials become smeared out over space. This smearing increases until the atoms – now more like waves than particles – overlap, becoming indistinguishable from one another. The resulting matter behaves like it’s one single entity with new properties the preceding solid, liquid or gas states lacked".
Now, in the new study the Tokyo researchers have shown superconductivity in a Bose-Einstein condensate. The feat was achieved by making a BEC out of a cloud of iron and selenium atoms.
The key to the discovery came from an overlap with a similar form of matter, called a Bardeen-Cooper-Shrieffer (BCS) regime. Like BECs, BCS regimes are made by cooling clouds of atoms almost to absolute zero, but the difference here is that when they do, the atoms slow down and line up. That means electrons can pass through them more easily, enabling superconductivity.
In practice, the discovery doesn’t have any direct applications for the general public, but deepening our understanding of the phenomenon can only help scientists create better superconductors in future.