Mr. Brad Ramshaw
University of British Columbia

Quantum oscillations in an underdoped high-Tc superconductor: exploiting the unique chemistry of YBa2Cu3O6.x

We have measured Fermi surface properties of the high temperature superconductor YBa2Cu3O6.59 via the Shubnikov-de Haas effect - oscillations in the resistivity as a function of magnetic field. Despite YBCO 6.59 being in the strongly-correlated "pseudogap" regime, our detailed data analysis shows that there are Fermi-liquid like quasiparticles at this doping, with no substantial renormalizations to electronic "g" factor which couples the quasiparticle spin to the magnetic field.

By exploiting the unique doping mechanism in YBCO, we have measured similar Fermi surface properties at three different oxygen ordered states in YBCO (Ortho II, Ortho V, and Ortho VIII), giving strong evidence that the oscillations are not a property of the chains unique to YBCO, but intrinsic to the copper-oxygen planes found in all cuprate high-Tc superconductors.

By manipulating the oxygen order we can control the doping with high resolution. This has allowed us to identify the precise doping level where the quantum oscillations disappear along with the negative Hall coefficient, suggesting that the two are related.