Electron spectral function and algebraic spin liquid for the normal   state of underdoped high $T_c$ superconductors
  We propose to describe the spin fluctuations in the normal state of underdoped high $T_{c}$ superconductors as a manifestation of an algebraic spin liquid. We have performed calculations within the slave-boson model to support our proposal. Under the spin-charge separation picture, the normal state (the spin-pseudogap phase) is described by massless Dirac fermions, charged bosons, and a gauge field. We find that the gauge interaction is a marginal perturbation and drives the mean-field free-spinon fixed point to a more complicated spin-quantum-fixed-point -- the algebraic spin liquid, where gapless excitations interact at low energies. The electron spectral function in the normal state was found to have a Luttinger-liquid-like line shape as observed in experiments. The spectral function obtained in the superconducting state shows how a coherent quasiparticle peak appears from the incoherent background as spin and charge recombine. 
Walter Rantner and Xiao-Gang Wen