Fermi surface reconstruction in hole-doped t-J models without long-range   antiferromagnetic order
  We calculate the Fermi surface of electrons in hole-doped, extended t-J models on a square lattice in a regime where no long-range antiferromagnetic order is present, and no symmetries are broken. Using the "spinon-dopon" formalism of Ribeiro and Wen, we show that short-range antiferromagnetic correlations lead to a reconstruction of the Fermi surface into hole pockets which are not necessarily centered at the antiferromagnetic Brillouin zone boundary. The Brillouin zone area enclosed by the Fermi surface is proportional to the density of dopants away from half-filling, in contrast to the conventional Luttinger theorem which counts the total electron density. This state realizes a "fractionalized Fermi liquid" (FL*), which has been proposed as a possible ground-state of the underdoped cuprates; we note connections to recent experiments. We also discuss the quantum phase transition from the FL* state to the Fermi liquid state with long-range antiferromagnetic order. 
Matthias Punk and Subir Sachdev
cond-mat.str-el