Electrical switching of momentum-indirect quadrupolar excitons

Quadrupolar excitons represent a novel class of quasiparticles, distinguished by their unique many-body interactions and electric field tunability. Here, by using gate-dependent photoluminescence spectroscopy and ab-initio calculations, we uncover the field-polarizability of momentum indirect excitons in few-layer TMDs and confirm their quadrupole character. These quadrupolar excitons features a characteristic quadratic Stark shift at low electric fields and a unique electric-field-induced quadrupole-to-dipole switch arising from a transition crossover. We further investigate their sensitivity to electrostatic doping and excitation power, uncovering distinct doping and density dependent responses. Moreover, the spatially extended wavefunction of quadrupolar excitons allows their use as highly sensitive probes, offering new possibilities for layer and interface engineering. Our results demonstrate unprecedented control over quadrupolar exciton properties through electric field, layer and interface engineering, and we establish our system as a versatile platform for realizing and manipulating quadrupolar excitons beyond symmetric TMD heterotrilayers.