Microwave absorption in the cores of the Abrikosov vortices pinned by artificial insulator inclusion

Abstract

The spectrum of core excitations of the Abrikosov vortex pinned by a dielectric inclusion or nanoholes of the size of the coherence length is considered using the Bogoliubov-deGennes equations beyond the semiclassical approximation. While the lowest excitation, mini-gap, in the unpinned (or pinned by a metallic defect) vortex is of the order of Delta(2)/epsilon(F), it becomes of the order of the superconducting gap Delta. The reconstruction of the quasiparticle excitations' spectrum has a significant impact on optical properties and on the tunneling density of states. We calculate the absorption amplitude and point out that, while in STM the energy gap Delta(DOS) is between a quasiparticles state with angular momentum mu(e) = mu(s) > 1/2 and quasi-hole with mu(h) = mu(s) the microwave absorption gap, Delta(dir) is between states with mu(e) = mu(h) + 1. It is shown that Delta(dir) > Delta(DOS). The large mini-gap might play a role in magneto-transport phenomena broadly associated with the "superconductor-insulator" transition in quasi 2D systems in which small insulating inclusions are generally present. (C) 2012 Elsevier B. V. All rights reserved.