Fermi-surface reconstruction and charge density waves in Tl2Ba2CuO6+δ

Hall effect and quantum oscillation measurements on high temperature cuprate superconductors show that underdoped compositions have small Fermi surface pockets whereas when heavily overdoped, a single much larger pocket is found. It has been proposed that the origin of this change in electronic structure is related to the closing of the pseudogap. Our recent ID32 experiment shows that the clean overdoped single-layer cuprate Tl2Ba2CuO6+δ (Tl2201) displays charge density wave (CDW) order with a remarkably long correlation length ξ≈200 Å which disappears above a hole doping p_(CDW )≈0.265. We have proposed that the evolution of the electronic properties of Tl2201 as the doping is lowered may be due to growth of the CDW gap below p_(CDW )rather than the opening of the pseudogap. To test this hypothesis, we propose to measure how the CDW in Tl2201 evolves with doping.