Electron pairing in the quantum Hall regime due to neutralon exchange

The behavior of electrons in condensed matter systems is mostly determined by the repulsive Coulomb interaction. However, under special circumstances, the Coulomb interaction can be effectively attractive, giving rise to electron pairing in unconventional superconductors and specifically designed mesoscopic setups. In quantum Hall systems, electron interactions can play a particularly important role due to the huge degeneracy of Landau levels, leading, for instance, to the emergence of quasiparticles with fractional charge and anyonic statistics. Quantum Hall Fabry-Perot interferometers (FPI) have attracted increasing attention due to their ability to probe such exotic physics. In addition, such interferometers are affected by electron interactions themselves in interesting ways. Recently, experimental evidence for electron pairing in a quantum Hall FPI was found [Choi et al., Nat. Commun. 6, 7435 (2015)]. Theoretically describing an FPI in the limit of strong backscattering and under the influence of a screened Coulomb interaction, we compute electron shot noise and indeed find a two-fold enhanced Fano factor for some parameters, indicative of electron pairing. This result is explained in terms of an electron interaction due to exchange of neutral interedge plasmons, so-called neutralons.