Fig. 3
From: Broken rotational symmetry on the Fermi surface of a high-Tc superconductor
Two possible anisotropic CDW reconstruction schematics forYBa2Cu3O6.58. The unreconstructed cuprate Fermi surface is a large hole-like cylinder.18,32,65 a The bilayer copper oxide planes of YBa2Cu3O6+δ give rise to bonding and anti-bonding bands, whose interlayer velocities have opposite signs (one quarter of the Fermi surface has been cut away for clarity). b–e are projections of this surface into the k a–k b plane, from k z = −π/c to k z = 0, before (b and d) and after (c and e) Fermi surface reconstruction. The color scale signifies the sign of v z. The upper two panels involve two anisotropic CDWs, with Q 1 = (δ,0,1/2) and Q 2 = (δ,0,0) (refs 9, 11, 58), whereas the bottom two panels are the result of a large nematic distortion.59 followed by uni-axial CDW reconstruction with Q = (δ,0,0), and where δ ≈ 0.3 according to X-ray scattering measurements.9 Multiple Fermi surface sections, between which magnetic breakdown is possible,17,24,39,40 are present after reconstruction: for clarity we color only one section
