Structure of the charge density wave in cuprate superconductors: Lessons from NMR

Using a mix of numerical and analytic methods, we show that recent NMR O-17 measurements provide detailed information about the structure of the charge-density wave (CDW) phase in underdoped YBa2Cu3O6+x. We perform Bogoliubov-de Gennes (BdG) calculations of both the local density of states and the orbitally resolved charge density, which are closely related to the magnetic and electric quadrupole contributions to the NMR spectrum, using a microscopic model that was shown previously to agree closely with x-ray experiments. The BdG results reproduce qualitative features of the experimental spectrum extremely well. These results are interpreted in terms of a generic "hot-spot" model that allows one to trace the origins of the NMR line shapes. We find that four quantities-the orbital character of the Fermi surface at the hot spots, the Fermi surface curvature at the hot spots, the CDW correlation length, and the magnitude of the subdominant CDW component-are key in determining the line shapes.