Resonant x-ray scattering explorations of charge order and broken symmetries in underdoped cuprates

Abstract

The spontaneous self-arrangement of electrons into periodically modulated patterns, a phenomenon commonly termed as charge order or charge-density-wave, has recently resurfaced as a prominent, universal ingredient for the physics of high-temperature superconductors. Its antagonist coexistence with superconductivity, together with its possible connection to a quantum critical point beyond optimal doping, are symptomatic of a very fundamental role played by this symmetry-broken collective electronic state. Resonant x-ray scattering (RXS) has rapidly become the technique of choice for the study of charge order in momentum space, owing to its ability to directly identify a breaking of translational symmetry in the electronic density. Here we will review our RXS work on underdoped Bi2201 and electron-doped NCCO to detect charge-density-waves even in presence of short-ranged order, exploring a realm previously accessible using real-space probes. In addition, we will discuss how the information available from the full two-dimensional momentum space can be used to demonstrate the presence of charge stripes in YBCO. Finally, we will review our explorations of polarization-dependent scattering intensities to uncover the local symmetry in the charge distribution around the Cu atoms, which was found to be predominantly of a d-wave bond-order type.