Excitons in the fractional quantum Hall effect

As a Coulomb-driven bound state of an electron and a hole, excitons obey bosonic quantum statistics, with its low-temperature ground state described by the Bose-Einstein condensation. In the presence of the fractional quantum Hall effect (FQHE), exciton pairing adds a new dimension to the complex phase space, promising to unlock exotic quantum phases of matter characterized by unique two-component correlations. In this talk, we explore the coexistence of excitonic pairing and the FQHE in the quantum Hall graphene bilayer system. We demonstrate that exciton formation is crucial in defining FQHE order. Specifically, we show that introducing exciton pairing within the conventional Jain sequence of FQHE states enables a new electronic order, which is described as the fractional analogue of exciton condensation. Remarkably, excitonic pairing reduces the energy required for quasiparticle excitation, opening the possibility of excitons with fractionally charged constituents as a low-energy collective mode. These findings broaden our understanding of exciton physics and offer fresh insights into correlated quantum phases in low-dimensional systems.