Probing the Gauge Structure of High-Temperature Superconductors

Abstract

We suggest that a spin-charge separating ansatz, leading to non-Abelian SU (2)⊗ US(1) gauge symmetries in doped antiferromagnets, proposed earlier as a way of describing Kosterlitz–Thouless superconducting gaps at the nodes of the gap of d-wave (high- Tc ) superconductors, may also lead to a pseudogap phase, characterized by the formation of (nonsuperconducting) pairing and the absence of phase coherence. The crucial assumption is again the presence of electrically charged Dirac fermionic excitations (holons) about the points of the (putative) Fermi surface in the pertinent phase of the superconductor. We present arguments in support of the rôle of nonperturbative effects (instantons) on the onset of the pseudogap phase. As a means of probing such gauge interactions experimentally, we perform a study of the scaling of the thermal conductivity with an externally-applied magnetic field, in certain effective models involving gauge and/or four-fermion (contact) interactions.