Resonant x-ray scattering investigations of orbital/nematic and charge density wave orders in cuprate superconductors

Charge density wave (CDW) order has been established as a generic feature of the cuprate phase diagram, competing and co-existing with superconductivity. In addition to being a modulation of charge density, CDW order couple to orbital degrees of freedom, including (Q_x = Q_y = 0) orbital/nematic order. How these orders manifest and couple to each other can depend on the structure of the material and hole doping, and may play an important role in how CDW order varies amongst the different cuprates. In this talk, we explore the relationship between structural distortions, (Q_x = Q_y = 0) nematic/orbital order and CDW using equilibrium and pump/probe resonant x-ray scattering measurements in the (La,M)₂CuO₄ family of cuprate superconductors. These measurements demonstrate orbital/nematic order to be coupled to but distinct from CDW order. We will also show nematic order to be present in underdoped cuprates, but vanish above the pseudogap critical doping, p*, and temperature, T* in overdoped cuprates.