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

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.