  Recently the ATLAS and CMS collaborations have reported evidence of a
diphoton excess which may be interpreted as a pseudoscalar boson S with a mass
around 750 GeV. To explain the diphoton excess, such a boson is coupled to the
Standard Model gauge fields via SFF-dual operators. In this work, we consider
the implications of this state for early universe cosmology; in particular, the
S field can acquire a large vacuum expectation value due to quantum
fluctuations during inflation. During reheating, it then relaxes to its
equilibrium value, during which time the same operators introduced to explain
the diphoton excess induce a nonzero chemical potential for baryon and lepton
number. Interactions such as those involving right-handed neutrinos allow the
system to develop a non-zero lepton number, and therefore, this state may also
be responsible for the observed cosmological matter-antimatter asymmetry.
