Physicists from the National Institute of Scientific Research (INRS) in Canada have obtained new data on how two quantum states relate in cuprates - a family of copper-containing compounds discovered in 1986: superconductivity and the pseudogap. The work was published in the journal Nature Physics.
Superconductivity is the ability of a material to conduct electric current without energy losses. In cuprates it arises at relatively high temperatures, which makes them promising for more efficient power grids, medical equipment and quantum computers. However, the mechanism of the transition to the superconducting state is still unclear.
The key problem is the pseudogap, a special quantum state whose role remains a subject of debate. Some scientists assumed that it helps superconductivity arise, while others considered it a competing phenomenon. The team led by Professor Fabio Boschini decided to test this directly.
For the experiment, the researchers used a pulse of light to temporarily suppress superconductivity and then observed the material's response in real time. A setup based on time- and angle-resolved photoemission spectroscopy (TR-ARPES) made it possible for the first time to see the light-induced transient pseudogap and to gain access to electronic states hidden from conventional methods.
It turned out that when superconductivity is suppressed, a pseudogap appears in its place, and when superconductivity returns, the pseudogap disappears. This points to competition rather than cooperation between the two states and casts doubt on the hypothesis that the pseudogap serves as a precursor to superconductivity.
The study is fundamental in nature. The authors emphasize that it is important for understanding the behavior of cuprates and in the future may contribute to the creation of new-generation superconductors and more energy-efficient technologies. International partners also took part in the work, including the Center for Computational Quantum Physics at the Flatiron Institute in New York.