The sign of vortex charges in high temperature superconductors

Abstract

Based on a widely adopted effective model Hamiltonian with competing antiferromagnetic (AF) and d-wave superconductivity (DSC) interactions, the vortex charge in high T c superconductors is investigated by solving self-consistently the Bogoliubov-de Gennes equations. The band parameters are chosen in such a way that the obtained local densities at and far away from the vortex center are in qualitative agreement with the STM measurements on YBCO. Both the hole-rich normal and electron-rich AF vortices are found, depending on the strength of induced AF order. The vortex charge is strongly influenced by the competing effects from the AF order and the DSC order at the vortex core. By tuning the on-site Coulomb repulsion U or the doping parameter δ, a transition between the positive and negative vortex charges may occur. Recent NMR and Hall effect experiments on vortex charges can be understood in terms of the present results. New imaging experiments should be able to probe the vortex charge directly.