Quadrupolar and Dipolar Excitons in Bilayer 2H-MoSe₂

We report the experimental observation of quadrupolar exciton states in the reflectance contrast spectrum of 2H-stacked bilayer MoSe₂. The application of a vertical electric field results in a quadratic energy redshift of these quadrupolar excitons, in contrast to the linear energy splitting observed in the coexisting dipolar excitons within the bilayer MoSe₂. We perform helicity-resolved reflectance contrast measurements to investigate the spin and valley configurations of the quadrupolar exciton states as a function of applied vertical electric and magnetic fields. Comparing our results with a phenomenological coupled-oscillator model indicates that the electric- and magnetic-field dependence of the quadrupolar exciton states can be attributed to the intra- and intervalley hybridization of spin-triplet interlayer excitons with opposite permanent dipole moments, mediated by interlayer hole tunneling. These results position naturally stacked MoSe₂ bilayers as a promising platform to explore electric-field-tunable many-body exciton phenomena.