  We investigate spin relaxation dynamics of interlayer excitons in a
MoSe2/MoS2 heterostructure induced by the Rashba effect. In such a system,
Rashba interactions arise from an out-of-plane electric field due to
photo-generated interlayer excitons inducing a phonon-assisted intravalley spin
relaxation. We develop a theoretical description based on a microscopic
approach to quantify the magnitude of Rashba interactions and test these
predictions via time-resolved Kerr rotation measurements. In agreement with the
calculations, we find that the Rashba-induced intravalley spin mixing becomes
the dominating spin relaxation channel above T = 50 K. Our work identifies a
previously unexplored spin-depolarization channel in heterostructures which can
be used for ultrafast spin manipulation.
