Bilayer Excitons in the Laughlin Fractional Quantum Hall State

The Laughlin state embodies a universal class of fractional quantum Hall effects arising in two-dimensional electron systems subjected to strong perpendicular magnetic fields. Traditionally viewed as a single-component phase, it hosts fractionally charged quasiparticles arising from correlations within one electron species. Here, we explore a new regime in which two intra-species Laughlin states are coupled through inter-species Coulomb interactions in a quantum Hall graphene bilayer structure. Although quasiparticle excitations in each layer typically possess charge gaps of tens of Kelvin, we find that this energy scale is drastically reduced by interlayer excitonic pairing between quasiparticles and quasiholes. This establishes a previously unobserved form of excitonic pairing in which the constituent particles themselves carry fractional charge. Moreover, we identify robust signatures of such pairing at an unexpected even-denominator fractional quantum Hall state corresponding to a filling of 3/8 per layer. Together, these findings reveal a new avenue for realizing and probing emergent anyonic exciton phases in quantum Hall bilayers.