Vortex core near planar defects in a clean layered superconductor

Abstract

We investigate the structure of quasiparticle states localized in a core of an Abrikosov vortex in a clean layered superconductor in the presence of planar defects. It is shown that even a highly transparent defect opens a minigap at the Fermi energy. Its magnitude ${E}_{g}\ensuremath{\sim}\mathrm{\ensuremath{\Delta}}\sqrt{R}$ exceeds the mean level spacing for the chiral branch ${\ensuremath{\omega}}_{0}\ensuremath{\sim}{\mathrm{\ensuremath{\Delta}}}^{2}/{E}_{F}$, already for very small values of the reflection coefficient off the defect $R\ensuremath{\ll}1$ ($\mathrm{\ensuremath{\Delta}}$ is the bulk gap). For $R\ensuremath{\gtrsim}\sqrt{\mathrm{\ensuremath{\Delta}}/{E}_{F}}$, formation of the minigap is accompanied by the appearance of subgap states localized along the defect, in accordance with A. V. Samokhvalov et al., Phys. Rev. B 102, 174501 (2020). The minigap takes its maximal value for the vortex located right at the defect, decreases with increasing the distance $b$ from the defect, and closes when ${k}_{F}b\ensuremath{\sim}(\mathrm{\ensuremath{\Delta}}/{\ensuremath{\omega}}_{0})\sqrt{R}$. We also study various configurations of several planar defects (few crossing planes, stars, periodic structures). Although the minigap remains, a strong commensurability effect is observed. For two crossing planar defects, the magnitude of the minigap strongly depends on how close the intersection angle is to a rational fraction of $\ensuremath{\pi}$.

Topics & Concepts