Topological vortex chain realized in type-II superconductors

In type-II superconductors, the Caroli-de Gennes-Matricon (CdGM) states were predicted as the low-energy quasiparticle excitations around a single Abrikosov vortex. For a periodic vertex lattice, the quantum tunneling effect between intersite CdGM states leads to the formation of Bloch-like bands inside the superconducting gap. In contrast to normal solids, such type of Bloch band describes the behaviors of Bogoliubov quasiparticles with the particle-hole symmetry naturally preserved. Here, we carry out theoretical studies on the potential topological properties harbored by these exotic Bloch bands. First, we investigate the quasiparticle excitations around an isolated magnetic vortex in the presence of Rashba spin-orbit coupling (SOC), which is demonstrated to lift the doubly degenerate CdGM states. Next, we construct a one-dimensional (1D) vortex chain and explore the SOC-induced band gap opening around the Fermi level. Based on symmetry analysis, the opened band gap possesses odd parity, indicating that the vortex chain essentially mimic a Kitaev chain, which is characterized by Majorana end modes. These findings can be naturally extended to 2D vortex lattice, thus providing generic appealing platforms for realizing and manipulating Majorana fermions.