Fermi surface in YBa2Cu3O6.9: Evidence from angle-resolved photoemission spectroscopy and positron two-dimensional angular correlation of annihilation radiation

Abstract

We assess the evidence regarding the geometry of the Fermi surface in ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{6.9}$ obtained from angle-resolved photoemission and positron two-dimensional angular correlation of annihilation radiation experiments. A detailed picture of the Fermi-surface topology of this system appears to be emerging, based on a comparison of the above-mentioned experiments with each other and with local-density-approximation calculations, although whether the Fermi surface is a manifestation of true Fermi-liquid behavior is in dispute. Some implications of these results are discussed.