Exploring the connections between electronic instabilities and lattice strain in cuprate superconductors

The high-temperature superconductors were discovered in 1986. Over 30 years of experimental and theoretical work have revealed a plethora of details, but a full and convincing microscopic description of the superconductivity remains elusive. However, it is clear that the copper-oxygen planes are the seat of the superconductivity, and that these planes are highly susceptible to range of electronic instabilities. The most obvious of these is superconductivity - the formation of Cooper pairs. One other strong commonality is the appearance of the pseudogap region. The primary characteristic of this region is a partial loss of electronic density of states at the Fermi level. A huge amount of work has been done to try and identify the driving mechanism behind the formation of this pseudogap region, but it remains unclear if it is associated with a true phase transition. In this research project, we will investigate the electronic instabilities associated with the copper-oxygen planes, using two primary techniques. We will explore the static response of the copper-oxygen planes using high energy X-ray diffraction and small angle X-ray scattering, and then the dynamics using X-ray photon correlation spectroscopy. The long-range lattice strain, both static and dynamic, shows strong temperature changes that appear to correlate to these electronic instabilities. In this project we will measure these effects rigorously to explore this connection, and address the nature of this region.