Electric field dependence of the flux-flow resistance and the electronic vortex structure in the cuprate superconductor Nd2-xCexCuOy

In the temperature limit T much less than T-c c-axis oriented films of the cuprate super-conductor Nd2-xCexCuOy display an intrinsic step structure of the flux-flow resistance. Under current bias hysteretic voltage steps appe ar, whereas under quasi voltage bias negative differential resistance (NDR) is observed. For explaining these instabilities, we propose an electronic structure in the mixed state, consisting of subbands between the Fermi ener gy and the superconducting energy gap. The subbands originate from the Andr eev bound states in the core of an isolated vortex, because of the interact ion between vortices. Bloch oscillations of the quasiparticles in the narro w subbands are proposed as the mechanism generating the NDR.