  Using the semiclassical approach to the energy levels of the fermions bound
to the vortex core, we found the difference between the states in nonchiral and
chiral superconductors, determined by the Berry phase. The bound states of
fermions in the singly quantized vortex in the layered superconductor with the
symmetry of superfluid 3He-A is E=n\omega_0 (as distinct from E=(n+1/2)\omega_0
in s-wave superconductor) and thus contains the state with exactly zero energy.
This is in accordance with the result obtained in microscopic theory by Kopnin
and Salomaa. Using this approach for calculations of the effect of impurities
on the spectrum of bound state we reproduced the Larkin-Ovchinnikov result for
single impurity in s-wave vortex: the spectrum has the double period \Delta
E=2\omega_0 and consists of two equdistant sets of levels. The same approach
however shows that the single impurity does not change the spectrum E=n\omega_0
in the p-wave vortex .

Superconductivity