Chern-Simons Modified-RPA Eliashberg Theory of the nu=1/2+1/2 Quantum Hall Bilayer

TL;DR

This paper introduces a modified RPA Eliashberg theory for the nu=1/2+1/2 quantum Hall bilayer, resolving previous divergences and ambiguities, and analyzes pairing channels of composite fermions and holes.

Contribution

It develops a divergence-free, single Landau level projection of CSRPAE theory, providing new insights into pairing mechanisms in quantum Hall bilayers.

Findings

Angular momentum channel l=+1 dominates for composite fermion pairing.

Channel l=0 dominates for composite fermion electron-hole pairing.

Pairing strengths in both descriptions are nearly identical, confirming duality.

Abstract

The nu=1/2+1/2 quantum Hall bilayer has been previsously modeled using Chern-Simons-RPA-Eliashberg (CSRPAE) theory to describe pairing between the two layers. However, these approaches are troubled by a number of divergences and ambiguities. By using a "modified" RPA approximation to account for mass renormalization, we can work in a limit where the cyclotron frequency is taken to infinity, effectively projecting to a single Landau level. This, surprisingly, controls the important divergences and removes ambiguities found in prior attempts at CSRPAE. Examining BCS pairing of composite fermions we find that the angular momentum channel l=+1 dominates for all distances d between layers and at all frequency scales. Examining BCS pairing of composite fermion electrons in one layer with composite fermion holes in the opposite layer, we find the l=0 pairing channel dominates for all d and all frequencies. The strength of the pairing in these two different descriptions of the same phase of matter is found to be almost identical. This agrees well with our understanding that these are two different but dual descriptions of the same phase of matter.