Seminar via Zoom By Eduardo de Silva Neto, Yale University
Title: Non-monotonic electron interactions and charge order in the copper oxide plane
Host: Vladimir Dobrosavljevic
Abstract: In strongly correlated systems the strength of Coulomb interactions between electrons, relative to their kinetic energy, plays a central role in determining their emergent quantum mechanical phases. I will discuss resonant x-ray scattering experiments on Bi2Sr2CaCu2O8+δ, a prototypical cuprate superconductor that probe electronic correlations within the CuO2 plane. We discovered a dynamic quasi-circular pattern in the x-y scattering plane with a radius that matches the wave vector magnitude of the well-known static charge order . Along with doping- and temperature-dependent measurements, our experiments reveal a picture of charge order competing with superconductivity where short-range domains along x and y can dynamically rotate into any other in-plane direction. This quasi-circular spectrum, a hallmark of Brazovskii-type fluctuations, has immediate consequences to our understanding of rotational and translational symmetry breaking in the cuprates. I will discuss how the combination of (screened) short- and long-range Coulomb interactions results in an effective non-monotonic potential (see figure) that may determine the quasi-circular pattern. – I will also present experiments where we demonstrate a very modest amount of uniaxial stress (0.1GPa causing 0.04% uniaxial strain) results in a very large reduction of the onset of charge stripes (~50K) . I will also disucss how to interpret these results in the context of the quasi-circular dynamic correlations.
 F. Boschini, et al. Nature Communications 12, 597 (2021). https://doi.org/10.1038/s41467-020-20824-7
 T.J. Boyle, et al. Physical Review Research (accepted, 2021). https://arxiv.org/abs/2012.09665