On chiral magnetic effect in Weyl superfluid 3He-A
G. E. Volovik
Low Temperature Laboratory, Department of Applied Physics, Aalto University, PO Box 15100, FI-00076 AALTO, Finland
Landau Institute for Theoretical Physics RAS, 119334 Moscow, Russia
Abstract
In the theory of the chiral anomaly in relativistic quantum field theories
(RQFT) some results depend on regularization scheme at ultraviolet. In the
chiral superfluid 3He-A, which contains two Weyl points and also
experiences the effects of chiral anomaly, the "trans-Planckian" physics is
known and the results can be obtained without regularization. We discuss
this on example of the chiral magnetic effect (CME), which has been observed
in 3He-A in 90's [Krusius1998]. There are two forms of the
contribution of the CME to the Chern-Simons term in free energy, perturbative
and non-perturbative. The perturbative term comes from the fermions living in
the vicinity of the Weyl point, where the fermions are "relativistic" and
obey the Weyl equation. The non-perturbative term originates from the deep
vacuum, being determined by the separation of the two Weyl points in momentum
space. Both terms are obtained using the Adler-Bell-Jackiw equation for
chiral anomaly, and both agree with the results of the microscopic
calculations in the "trans-Planckian" region.
Existence of the two nonequivalent forms of the Chern-Simons term
demonstrates that the results obtained within the RQFT depend on the specific
properties of the underlying quantum vacuum and may reflect different
physical phenomena in the same vacuum.