Topologically stable gapped state in a layered superconductor.

Abstract

We show that a layered superconductor, described by a two-component order parameter, has a gapped state above the ground state, topologically protected from decay, containing flow and counterflow in the absence of an applied magnetic field. This state is made of skyrmions, breaks time reversal symmetry and produces a weak local magnetic field. We estimate the density of carriers that condense into the pseudogap of the cuprate superconductors based on the assumption that the pseudogap is a skyrmion state.