Quasiparticle creation and condensation in a resonating-valence-bond superconductor.

Abstract

We present a formulation of the resonating-valence-bond theory of the large-$U$ one-band Hubbard model in two dimensions, in which the correlated ground state of the system is represented as a fluid of mobile singlet bonds. We describe this fluid as a quantum fluid of interacting hardcore bosons, and a ground-state wave function for the interacting bosons is studied in which two-body correlations are introduced by applying techniques previously developed in Laughlin's theory of the fractional quantum Hall problem. The resulting many-particle state in this formulation exhibits an incipient momentum space condensation and a class of particlelike excitations in the form of quantized vortices which possess fractional particle number, and interesting dynamics. Application of this model to the doped state reveals a mechanism by which the electrostatic repulsive interactions between the charged quasiparticles in the doped fluid stabilize the resonating state relative to the doped N\'eel state at discrete well-correlated commensurate hole concentrations. A superconducting state in this doped fluid arises from a condensation which pairs the charged quasiparticles; it is identified as the most stable of a hierarchy of possible condensed quasiparticle states. The condensed state exhibits many properties associated with conventional superconductivity, including dissipationless flow of current, Meissner effect, and flux quantization in units of $\frac{\mathrm{hc}}{2e}$.