Emergent U(1) gauge theory with fractionalized boson/fermion from the Bose condensation of excitons in a multiband insulator

Fractionalized phases are studied in a low energy theory of exciton Bose condensate in a multiband insulator. It is shown that U(1) gauge theory with either fractionalized boson or fermion can emerge out of a single model depending on the coupling constants. Both the statistics and spin of the fractionalized particles are dynamically determined, satisfying the spin-statistics theorem in the continuum limit. We present two mutually consistent …