Excitonic Superfluid to pseudo-spin density wave transition in bilayer quantum Hall systems

TL;DR

This paper develops a quantum Ginzburg-Landau theory to describe a phase transition in bilayer quantum Hall systems from an excitonic superfluid to a pseudo-spin density wave, predicting a square lattice structure and explaining experimental drag phenomena.

Contribution

It introduces a theoretical framework for the ESF to PSDW transition, highlighting the role of magneto-roton minimum collapse and correlated vacancy hopping.

Findings

Square lattice is the favored PSDW structure.

Large, temperature-dependent drag explained by vacancy hopping.

Comparison with microscopic calculations supports the theory.

Abstract

We construct a quantum Ginsburg-Landau theory to study the quantum phase transition from the excitonic superfluid (ESF) to a possible pseudo-spin density wave (PSDW) at some intermediate distances driven by the magneto-roton minimum collapsing at a finite wavevector. We analyze the properties of the PSDW and explicitly show that a square lattice is the favorite lattice. We suggest that correlated hopping of vacancies in the active and passive layers in the PSDW state leads to very large and temperature dependent drag consistent with the experimental data. Comparisons with previous microscopic numerical calculations are made. Further experimental implications are given.