Opto-electronic Transport Measurements of Doubly Charged Excitonic Boson

Bilayer excitonic physics in transition metal dichalcogenides (TMDs) has recently gained renewed interest for its potential to enable light-induced superconductivity. Most studies have focused on interlayer excitons - neutral quasiparticles theorized to support superfluid transport via counterflow drag effects. Here, we explore a less studied but more direct route towards superconductivity through a charged bosonic state, called the “Quaternion”.

The Quaternion is formed due to the pairing of a charge in the topmost TMD layer with a similarly charged Trion in the bottom layer of a closely coupled bilayer heterostructure, placed near a metallic substrate. Our previous magneto-photoluminescence (PL) measurements [1,2] demonstrated that the Quaternion acts as a composite boson with an effective charge of ±2e. Building on this, we now show through four-terminal transport measurements with variable wavelength-dependent pumping, there is a dramatic reduction in electrical resistance across the device channel attributed to the transport mediated by the Quaternion. Furthermore, using PL imaging, we directly extract the scattering length and mobility of the Quaternion as a function of temperature and in-plane electric field strength.

Together, these measurements establish a foundation for probing the BEC–BCS crossover in charged excitonic systems and advancing the pursuit of light-induced superconductivity in TMD heterostructures.