Axion assisted Schwinger effect

We point out an enhancement of the pair production rate of charged fermions in a strong electric field in the presence of time dependent classical axion-like background field, which we call axion assisted Schwinger effect. While the standard Schwinger production rate is proportional to exp(-pi(m(2) + p(T)(2))/E), with m and pT denoting the fermion mass and its momentum transverse to the electric field E, the axion assisted Schwinger effect can be enhanced at large momenta to exp(- pi m(2)/E). The origin of this enhancement is a coupling between the fermion spin and its momentum, induced by the axion velocity. As a non-trivial validation of our result, we show its invariance under field redefinitions associated with a chiral rotation and successfully reproduce the chiral anomaly equation in the presence of helical electric and magnetic fields. We comment on implications of this result for axion cosmology, focussing on axion inflation and axion dark matter detection.

Automated summary

This study highlights an enhancement in the pair production rate of charged fermions in a strong electric field with the presence of a time dependent classical axion-like background field, termed as the axion assisted Schwinger effect. The enhancement is attributed to coupling between fermion spin and momentum induced by the axion velocity. This result has implications for axion cosmology, particularly in axion inflation and axion dark matter detection.