We propose that underdoped high-$T_c$ superconductors are described by an algebraic spin liquid (ASL) at high energies, which undergoes a spin-charge recombination transition at low energies. The spin correlation in the ASL is calculated via its effective theory—a system of massless Dirac fermions coupled to a U(1) gauge field. We find that without fine-tuning any parameters the gauge interaction strongly enhances the staggered spin correlation even in the presence of a large single-particle pseudogap. This allows us to show that the ASL plus spin-charge recombination picture can explain many highly unusual properties of underdoped high-$T_c$ superconductors.

• Received 28 January 2002

DOI:https://doi.org/10.1103/PhysRevB.66.144501