Spectrum of bound fermion states on vortices in 3He-B
M. A. Silaev
Institute for Physics of Microstructures RAS, 603950 Nizhny Novgorod, Russia
Low Temperature Laboratory, Helsinki University of Technology, 02150 Espoo, Finland
PACS: 74.25.-q, 74.78.Na
Abstract
We study subgap spectra of fermions localized within vortex cores
in 3He-B. We develop an analytical treatment of the low-energy states and
consider the characteristic properties of fermion spectra for different
types of vortices. Due to the removed spin degeneracy the spectra of all
singly quantized vortices consist of two different anomalous branches
crossing the Fermi level. For singular o and u vortices the anomalous
branches are similar to the standard Caroli-de Gennes-Matricon ones and
intersect the Fermi level at zero angular momentum yet with different slopes
corresponding to different spin states. On the contrary the spectral
branches of nonsingular vortices intersect the Fermi level at finite angular
momenta which leads to the appearance of a large number of zero modes, i.e.
energy states at the Fermi level. Considering the v, w and uvw
vortices with superfluid cores we show that the number of zero modes is
proportional to the size of the vortex core.