Electronic properties of the vortex state in cuprate superconductors

The superconducting state of the cuprates in the presence of a magnetic fie ld has been investigated very actively in the past few years through measur ements of electrical and thermal transport, ac conductivity, specific heat, and other quantities. The observed behavior is not well understood; it pro bes the nature of quasiparticies, vortices, and their interactions in a sup erconductor with nodes in the pair amplitude. We summarize here experimenta l results and our attempts to understand the phenomena, (C) 1999 Academic P ress.