Topological transitions in electronic spectra: Crossover between Abrikosov and Josephson vortices

The electronic structure of a vortex line trapped by a planar defect in a type-II superconductor is analyzed within the quasiclassical approach of the Bogoliubov--de Gennes theory. The normal reflection of electrons and holes at the defect plane results in the topological transition in the spectrum and formation of a type of quasiparticle state skipping or gliding along the defect. This topological transition appears to be a hallmark of the initial stage of the crossover from the Abrikosov to the Josephson vortex type revealed in the specific behavior of the quantized quasiparticle levels and density of states. The increase in the resulting hard and soft gaps affects the vortex mobility along the defect plane and the splitting of the zero-bias anomaly in the tunneling spectral characteristics.