Tunnel transport and interlayer excitons in bilayer fractional quantum Hall systems

Abstract

In a bilayer system consisting of a composite-fermion Fermi sea in each layer, the tunnel current is exponentially suppressed at zero bias, followed by a strong peak at a finite bias voltage V_(max). This behavior, which is qualitatively different from that observed for the electron Fermi sea, provides fundamental insight into the strongly correlated non-Fermi liquid nature of the CF Fermi sea and, in particular, offers a window into the short-distance high-energy physics of this state. We identify the exciton responsible for the peak current and provide a quantitative account of the value of V_(max). The excitonic attraction is shown to be quantitatively significant, and its variation accounts for the increase of V_(max) with the application of an in-plane magnetic field. We also estimate the critical Zeeman energy where transition occurs from a fully spin polarized composite fermion Fermi sea to a partially spin polarized one, carefully incorporating corrections due to finite width and Landau level mixing, and find it to be in satisfactory agreement with the Zeeman energy where a qualitative change has been observed for the onset bias voltage [Eisenstein et al., Phys. Rev. B 94, 125409 (2016)]. For fractional quantum Hall states, we predict a substantial discontinuous jump in V_(max) when the system undergoes a transition from a fully spin polarized state to a spin singlet or a partially spin polarized state.