# Tunnel transport and interlayer excitons in bilayer fractional quantum Hall systems

## TL;DR

This paper investigates tunnel transport in bilayer fractional quantum Hall systems, revealing the role of excitons, the effects of magnetic fields, and spin polarization transitions, providing new insights into strongly correlated quantum states.

## Contribution

It offers a quantitative analysis of tunnel current peaks, identifies the exciton responsible, and predicts behavior during spin polarization transitions in bilayer fractional quantum Hall systems.

## Key findings

- Peak bias voltage $V_{max}$ is linked to excitonic attraction.
- Application of in-plane magnetic field increases $V_{max}$.
- Predicted discontinuous jump in $V_{max}$ during spin state transitions.

## 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 $V_{\rm max}$. 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 $V_{\rm max}$. The excitonic attraction is shown to be quantitatively significant, and its variation accounts for the increase of $V_{\rm max}$ 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 $V_{\rm max}$ when the system undergoes a transition from a fully spin polarized state to a spin singlet or a partially spin polarized state.