Vortex state in a doped Mott insulator - art. no. 064516

We analyze the recent vortex core spectroscopy data on cuprate superconduct ors and discuss what can be learned from them about the nature of the groun d state in these compounds. We argue that the data are inconsistent with th e assumption of a simple metallic ground state and exhibit characteristics of a doped Mott insulator. A theory of the vortex core in such a doped Mott insulator is developed based on the U(1) gauge-field slave boson model. In the limit of vanishing gauge-field stiffness such a theory predicts two ty pes of singly quantized vortices: an insulating "holon" vortex in the under doped and a metallic "spinon" vortex in the overdoped region of the phase d iagram. We argue that the holon vortex exhibits a pseudogap excitation spec trum in its core qualitatively consistent with the existing experimental da ta on Bi2Sr2CaCu2O8. As a rest of this theory we propose that the spinon vo rtex with a metallic core might be observable in the heavily overdoped samp les.