  Spin-charge conversion by inverse spin Hall effect or inverse
Rashba-Edelstein effect is prevalent in spintronics but dissipative. We propose
a dissipationless spin-charge conversion mechanism by an excitonic pseudospin
superfluid in an electron-hole double layer system. Magnetic exchange fields
lift singlet-triplet degeneracy of interlayer exciton levels in the double
layer system. Condensation of the singlet-triplet hybridized excitons breaks
both a U(1) gauge symmetry and a pseudospin rotational symmetry around the
fields, leading to spin-charge coupled superflow in the system. We demonstrate
the mechanism by deriving spin-charge coupled Josephson equations for the
excitonic superflow from a coupled quantum-dot model.
