Led by Dr. Claudio Giannetti, an international collaboration from ten institutes in six countries worked with scientists from the CLF to study the physics of high-temperature superconductors. The discovery of important new findings has been made possible thanks to the ultrashort laser pulses in the extreme-ultraviolet (EUV) energy range produced by Artemis.

Using this facility and performing time-resolved photoemission measurements, the team was able to observe the dynamics of electrons on the entire Fermi surface of a prototypical copper-based high-temperature superconductor (known as Bi2212) for the first time. This advancement, impossible to achieve with conventional laser sources, made it possible to study the nature of the so-called 'antinodal' electronic states for the first time.

The findings revealed a dramatic variation between the electronic dynamics in different regions of the Fermi surface. Moreover, measurements of the dynamics of the oxygen states were performed, which are relevant to understand the superconducting mechanisms.

Lead author Federico Cilento says “The results we achieved are relevant to the physics of superconductivity at high critical temperature. Namely, we discovered that the ubiquitous pseudogap phase, which is found in the wide majority of copper-based high temperature superconductors, is a state characterised by strong electronic correlation, that develop a gap on the Fermi-surface in the so-called antinodal region.

Furthermore, the findings revealed that a photoexcitation of the material produces the re-emergence of in-gap states that were suppressed by electronic correlations. At equilibrium, a freezing of the electrons moving along the copper-oxygen bond that is provoked by electronic correlations; when these are weakened by a sudden excitation, the material transiently becomes more metallic." 

Additional information on this exciting step forward in the world of superconductivity, is available on Science Advances: http://advances.sciencemag.org/content/4/2/eaar1998​

For more information on Artemis, go to: https://www.clf.stfc.ac.uk/Pages/Artemis.aspx​​