Single electron interference and capacitive edge mode coupling generates ϕ₀/2 flux periodicity in Fabry-Pérot...

Area of Science:

• Condensed Matter Physics
• Quantum Hall Effect
• Mesoscopic Physics

Background:

• Experimental observations of flux periodicity ϕ₀/2 in the integer quantum Hall regime were previously attributed to exotic electron pairing.
• Understanding interference phenomena in edge modes is crucial for advancing quantum electronics.

Purpose of the Study:

• To investigate the origin of the observed flux periodicity ϕ₀/2 in the integer quantum Hall regime.
• To clarify the role of electron pairing versus capacitive coupling in edge mode interference.
• To determine the effective charge of the interfering unit in the outermost edge mode.

Main Methods:

• Fabrication and operation of an AlGaAs/GaAs Fabry-Pérot interferometer in the integer quantum Hall regime (1 ≤ ν ≤ 3).
• Simultaneous measurement of bulk-edge and edge-edge couplings.
• Analysis of interference patterns to determine flux periodicity and effective charge.

Main Results:

• Observed interference with flux periodicity ϕ₀/2 for the outermost edge mode at integer fillings ν=2 and ν=3.
• Demonstrated that the ϕ₀/2 periodicity arises from capacitive coupling between isolated edge modes and the interfering outer edge, not electron pairing.
• Determined the interfering unit of charge for the outermost edge mode to be e^*=1 (normalized to electron charge).

Conclusions:

• The flux periodicity ϕ₀/2 in the studied quantum Hall system is explained by capacitive coupling, challenging previous electron pairing interpretations.
• The effective charge of the interfering unit in the outermost edge mode was experimentally determined to be equal to the electron charge.
• Fabry-Pérot interferometry provides an in operando method to measure the magnitude of interfering charge in quantum Hall edge states.