Photo-assisted current in the fractional quantum Hall effect as a probe of the quasiparticle operator scaling dimension

TL;DR

This paper proposes a method to determine the quasiparticle statistics in fractional quantum Hall systems by analyzing the phase shift in photo-assisted tunneling currents modulated by a quantum point contact.

Contribution

It introduces a novel approach linking the phase shift of the second harmonic of photo-assisted current to the quasiparticle operator scaling dimension in fractional quantum Hall edge states.

Findings

Phase shift of second harmonic relates to quasiparticle scaling dimension

Gate modulation can diagnose quasiparticle statistics

Method applicable to Laughlin quasiparticles

Abstract

We study photo-assisted transport for the edge states of a two dimensional electron gas in the fractional quantum Hall regime, pinched by a single quantum point contact. We provide a general expression of the photo-assisted current using a Keldysh-Floquet approach, when the AC drive is applied either directly to the edge states, or when it modulates the tunneling amplitude at the quantum point contact. Strikingly, for a simple cosine modulation of the tunneling amplitude, the phase shift of the second harmonic of the photoassisted current is directly related to the scaling dimension of the quasiparticle operators describing the fractional excitations. As the scaling dimension is intimately related to the statistics, our proposal of a gate modulation of the backscattered current provides a diagnosis of the statistics of Laughlin quasiparticles using a simple quantum point contact geometry.