Noise spectroscopy and interlayer phase-coherence in bilayer quantum Hall systems

TL;DR

This paper explores how noise measurements in bilayer quantum Hall systems can reveal details about interlayer phase coherence and collective excitations, offering new experimental approaches beyond traditional transport studies.

Contribution

It proposes using interlayer current and charge-imbalance noise measurements to probe collective modes and phase transitions in bilayer quantum Hall systems, providing novel experimental insights.

Findings

Current noise frequency relates to zero wavevector collective mode.

Potential noise above the system probes finite-wavevector modes.

Noise studies can distinguish between ordered and disordered phases.

Abstract

Bilayer quantum Hall systems develop strong interlayer phase-coherence when the distance between layers is comparable to the typical distance between electrons within a layer. The phase-coherent state has until now been investigated primarily via transport measurements. We argue here that interlayer current and charge-imbalance noise studies in these systems will be able to address some of the key experimental questions. We show that the characteristic frequency of current-noise is that of the zero wavevector collective mode, which is sensitive to the degree of order in the system. Local electric potential noise measured in a plane above the bilayer system on the other hand is sensitive to finite-wavevector collective modes and hence to the soft-magnetoroton picture of the order-disorder phase transition.