Tuning the non-linear interactions of hybrid interlayer excitons in bilayer MoS ₂ via electric fields

Abstract Non-linear interactions among quasi-particles, and in particular excitons, in condensed matter systems are central for a plethora of advanced phenomena and possible applications like correlated dipolar excitonic insulator and light-induced switching. Engineering excitonic non-linearities can be facilitated by controlling their internal structure, and especially their dipolarity. However, gaining such in-situ control of the effective interaction strength is a long-standing challenge. In this work, we directly probe the blueshift of the excitonic energies to gain insight into the non-linear exciton–exciton interactions in a bilayer MoS ₂ system subject to external field control. By applying an out-of-plane electric field, we polarize the excitons to enhance their mutual dipolar interactions, thereby deliberately favoring these repulsive contributions over competing attractive many-body corrections. We furthermore establish a fully microscopic theoretical description of these effects to explain the core experimental results. The tuning results in a significantly larger blueshift compared to the zero-field case and perspectively opens an avenue to even switch between repulsive and attractive interaction potentials. Our findings establish that strong nonlinearities can be tuned via an external electric field, providing a new degree of control over exciton interactions beyond density tuning alone.