Abstract
For the superconducting mixed state in the clean limit the electronic density of states N(ε) above and below the Fermi energy ε = 0 is given by the bound states in the vortex core, with the minigap ε0 as a prominent feature. Quasiclassically, N(ε) shows a steep increase near the energy gap Δ. Since N(ε) provides the phase space for quasiparticle scattering, these features are expected to strongly affect the flux-flow resistance. Our recent observation of two intrinsic flux-flow resistance steps in epitaxial films of Nd2 − xCexCuOy are explained in terms of these features of N(ε) near ε = ε0 and ε = Δ, respectively. The instabilities resulting for current-bias from an electric-field–dependent resistance are discussed in general terms.