Figure 1: Representation of the band structure by Fermi arcs.
From: Giant phonon anomaly associated with superconducting fluctuations in the pseudogap phase of cuprates
(a) The breakup of Fermi surface to 2 sub-bands a and b in (1, 1) and 
directions. QGPA is a wavevector connecting the two sub-bands, which is also the wavevector of the phonon anomaly. (b) Simplified model of Fermi arcs. Each Fermi arc is represented by a circular arc (shown red) with center Y, radius R, and terminates at the Umklapp surface. The Fermi velocity vF (blue arrow) is assumed to a have constant magnitude on the whole arc. Y is uniquely determined by the choices of the wavevector between arc tips to be 0.51π, and the hole concentration p=11.5%. These are typical values in ARPES experiments. ± are the signs of the d-wave symmetry factor γp at different regions in the Brillouin zone. Black dots on the arcs indicate positions of superconducting nodes.
