Local density of states around single vortices and vortex pairs: Effect of boundaries and hybridization of vortex core states

The profiles of local density of states (LDOS) around single vortices and vortex pairs in type-II superconductors are studied taking account of the interference of quasiparticle waves experiencing Andreev reflection within the vortex cores, hybridization of vortex core states, and normal reflection at the boundaries or defects. For subgap energy levels these interference effects reveal themselves in a nontrivial dependence of the positions of the LDOS peaks on the intervortex distance and sample size. The peak positions generally do not coincide with the superconducting phase singularity points. The LDOS profiles are calculated for three generic examples which can be realized, e.g., in mesoscopic superconductors: (i) vortex-vortex pair; (ii) vortex positioned near a flat boundary; (iii) vortex positioned in the center of a superconducting disk. The resulting evolution of the Andreev interference patterns could be observable by scanning tunneling spectroscopy techniques in mesoscopic superconductors or disordered vortex arrays.