Homogeneous versus Spiral Phases of Hole-doped Antiferromagnets: A   Systematic Effective Field Theory Investigation
  Using the low-energy effective field theory for magnons and holes -- the condensed matter analog of baryon chiral perturbation theory for pions and nucleons in QCD -- we study different phases of doped antiferromagnets. We systematically investigate configurations of the staggered magnetization that provide a constant background field for doped holes. The most general configuration of this type is either constant itself or it represents a spiral in the staggered magnetization. Depending on the values of the low-energy parameters, a homogeneous phase, a spiral phase, or an inhomogeneous phase is energetically favored. The reduction of the staggered magnetization upon doping is also investigated. 
C. Br\"ugger, C. P. Hofmann, F. K\"ampfer, M. Pepe, and U.-J. Wiese