Abstract
We model the underdoped cuprates using fermions moving in a background with local antiferromagnetic order. The antiferromagnetic order fluctuates in orientation, but not in magnitude, so that there is no long-range antiferromagnetism, but a “topological” order survives. The normal state is described as a fractionalized Fermi liquid (FL*), with electronlike quasiparticles coupled to the fractionalized excitations of the fluctuating antiferromagnet. The electronic quasiparticles reside near pocket Fermi surfaces enclosing total area (the dopant density), centered away from the magnetic Brillouin zone boundary. The violation of the conventional Luttinger theorem is linked to a “species doubling” of these quasiparticles. We describe phenomenological theories of the pairing of these quasiparticles, and show that a large class of mean-field theories generically displays a nodal-antinodal “dichotomy”: The interplay of local antiferromagnetism and pairing leads to a small gap near the nodes of the -wave pairing along the Brillouin zone diagonals, and a large gap in the antinodal region.
1 More- Received 15 November 2010
DOI:https://doi.org/10.1103/PhysRevB.83.224508
©2011 American Physical Society