Flux line in a d-wave uperconductor

The structure of the core of a vortex line in a d∞2−y2 superconductor is studied within Bogoliubov-de Gennes theory. Three regions of the vortex are identified: (1) The inner core which supports localized fermionic excitations, (2) The outer core where d-wave and extended s-wave pairing coexist and the fermionic excitations are gapped, (3) The asymptotic region where the superconductor is in a d∞2−y2 state and low-energy quasi particles are present. The outer core is found to consist of four domains where the superconductor is in an s ± id state. The change in the relative phase is confined to domain walls where the relative phase changes by π.