Topological invariant for superfluid 3He-B and quantum phase transitions
G. E. Volovik
Low Temperature Laboratory, Helsinki University of Technology, FIN-02015 HUT, Finland
Landau Institute for Theoretical Physics RAS, 119334 Moscow, Russia
We consider topological invariant describing the vacuum
states of superfluid 3He-B,
to the special class of time-reversal invariant topological insulators
Discrete symmetries important for classification of the topologically
distinct vacuum states
One of them leads to the additional subclasses of 3He-B states and
is responsible for
the finite density of states of Majorana fermions living
at some interfaces between the bulk states.
valued topological invariant is expressed in terms of the Green's function,
which allows us
to consider systems with interaction.