Electronic structure of vortices pinned by columnar defects in $p_x \pm i p_y$ superconductors

TL;DR

This paper investigates how columnar defects influence the electronic structure of vortices in chiral $p_x \, ext{±} \, i p_y$ superconductors, revealing significant effects on spectral branches and quasiparticle behavior.

Contribution

It provides a detailed analysis of vortex electronic structure modifications due to defects in chiral superconductors using Bogolubov-de Gennes theory, highlighting the role of angular momentum orientations.

Findings

Anomalous spectral branch is sensitive to angular momentum orientations.

Defects can invert quasiparticle angular momenta at positive energies.

Changes in spectral branches affect STM characteristics and vortex dynamics.

Abstract

The electronic structure of a vortex pinned by an insulating columnar inclusion in a type-II chiral $p_x \pm i p_y$ superconductor is studied within the Bogolubov-de Gennes theory. The structure of the anomalous spectral branch is shown to be strongly affected by the mutual orientations of the angular momenta of the center of mass and the relative motion of the two electrons in the Cooper pair. Being only slightly perturbed by the scattering at the defect for the zero sum of these angular momenta the anomalous spectral branch appears to change dramatically in the absence of such compensation. In the latter case the defect presence changes the anomalous branch slope sign at the Fermi level resulting in the quasiparticle angular momenta inversion at the positive energies and the impact parameters smaller than the defect radius. The experimentally observed consequences for the scanning tunneling microscopy characteristics and vortex dynamics are discussed.