Shining ultra-fast X-rays on the problem of high temperature superconductivity

The aim of project is to deepen the understanding of the mechanisms responsible for high critical temperature (high-Tc) superconductivity (SC) in cuprate superconductors, by investigating one of its key phenomena: the pseudogap. In the SC state, two electrons condense into a Cooper pair and result in an energy gap in spectroscopic measurement.

However, in cuprates, such a gap persists even above Tc and can seamlessly evolve into the SC gap. This is the so called pseudogap.

Whether the pseudogap precedes an SC gap or arises due to spectral suppression from competing orders, are the two main scenarios.

The origin of the pseudogap and its relation with the SC gap are the keys to understanding the mechanism(s) driving high-Tc SC - one of the central unsolved problems in modern physics. In this project, two techniques will be employed to examine each scenario´s possibility.

Time- and angle-resolved photoemission spectroscopy will be conducted to track the formation process of SC and pseudogap phases to uncover the underlying effects.

Additionally, double-electron photoemission spectroscopy, targeting the SC precursor scenario, will be implemented to directly detect Cooper pair emission. The measurements will be carried out at the Stanford based free-electron laser (LCLS-II).

The significance of the project lies in its potential to elucidate the origins of the pseudogap and shedding light on the underlying mechanism(s) of high-Tc superconductivity.