Underdoped cuprates exhibit a normal-state pseudogap, and their spins and doped carriers tend to spatially separate into 1D or 2D stripes. Some view these as central to superconductivity and others as peripheral and merely competing. Using ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{Cu}}_{1-y}{\mathrm{Zn}}_y{\mathrm{O}}_4$ we show that an oxygen isotope effect in $T_c$ and in the superfluid density can be used to distinguish between the roles of stripes and pseudogap and also to detect the presence of impurity scattering. We conclude that stripes and pseudogap are distinct, and both compete and coexist with superconductivity.

• Received 29 July 2004

DOI:https://doi.org/10.1103/PhysRevLett.94.237002