Duality and the Fractional Quantum Hall Effect

TL;DR

This paper explores the duality symmetry in the edge states of quantum Hall systems, showing how it relates different fractional and integer Hall conductivities and unifies various fractional quantum Hall states within a single framework.

Contribution

It demonstrates that the $O(d,d;\mathbb{Z})$ duality transforms Hall conductivities, relates integer and fractional QHEs, and reproduces known hierarchies and fractions, providing a unified theoretical framework.

Findings

Duality relates different Hall conductivities.

Edge spectra are identical for dually related Hall states.

Framework reproduces Haldane and Jain fractions.

Abstract

The edge states of a sample displaying the quantum Hall effect (QHE) can be described by a 1+1 dimensional (conformal) field theory of $d$ massless scalar fields taking values on a $d$-dimensional torus. It is known from the work of Naculich, Frohlich et al.\@ and others that the requirement of chirality of currents in this \underline{scalar} field theory implies the Schwinger anomaly in the presence of an electric field, the anomaly coefficient being related in a specific way to Hall conducvivity. The latter can take only certain restricted values with odd denominators if the theory admits fermionic states. We show that the duality symmetry under the $O(d,d;{\bf Z})$ group of the free theory transforms the Hall conductivity in a well-defined way and relates integer and fractional QHE's. This means, in particular, that the edge spectra for dually related Hall conductivities are identical, a prediction which may be experimentally testable. We also show that Haldane's hierarchy as well as certain of Jain's fractions can be reproduced from the Laughlin fractions using the duality transformations. We thus find a framework for a unified description of the QHE's occurring at different fractions. We also give a derivation of the wave functions for fractions in Haldane's hierarchy.