Protected Nodal Electron Pocket from Multiple-Q Ordering in Underdoped High Temperature Superconductors

A multiple wave vector (Q) reconstruction of the Fermi surface is shown to yield a profoundly different electronic structure to that characteristic of single wave vector reconstruction, despite their proximity in energy. We consider the specific case in which ordering is generated by Q(x) = [2 pi a, 0] and Q(y) [0, 2 pi b] (in which a = b = 1/4)-similar to those identified in neutron diffraction and scanning tunneling microscopy experiments-and more generally show that an isolated pocket adjacent to the nodal point k(nodal) = [+/-pi/2, +/-pi/2] is a protected feature of such a multiple-Q model, potentially corresponding to the nodal Fermi arcs observed in photoemission and the small size of the electronic heat capacity found in high magnetic fields-importantly, containing electron carriers which can yield negative Hall and Seebeck coefficients observed in high magnetic fields.