Aharonov–Bohm Oscillations in Bilayer Graphene Quantum Hall Edge State Fabry–Pérot Interferometers

Abstract

Bernal-stacked bilayer graphene exhibits a wealth of interaction-driven phenomena, including robust even-denominator fractional quantum Hall states. We construct Fabry–Pérot interferometers using a split-gate design and present measurements of the Aharonov–Bohm oscillations. The edge state velocity is found to be approximately 6 × 104 m/s at filling factor ν = 2 and decreases with increasing filling factor. The dc bias and temperature dependence of the interference point to electron–electron interaction induced decoherence mechanisms. These results pave the way for the quest of fractional and non-Abelian braiding statistics in this promising device platform.

Charge Oscillations in Bilayer Graphene Quantum Confinement Devices

“…High-quality monolayer and bilayer graphene-based quantum confinement devices use thin hexagonal-boron nitride (h-BN) sheets as gate dielectrics. − The resulting confinement potential is typically sharper than that in GaAs and the nearby gates offer effective screening. Aharonov–Bohm (AB) oscillations at integer quantum Hall states have been observed recently in monolayer graphene − and bilayer graphene (BLG), respectively. An electric-field-induced band gap in BLG makes it possible to adopt existing strategies in 2D semiconductors to construct mesoscopic devices.…”

“…The carrier density inside and outside the interferometer n bulk is tuned by a combination of the TG and GG. A strong advantage of the type-I design is the screening provided by the TG and GG, which improves the BLG quality , and reduces the charging energy of the interferometer, which was critically important in the observation of fractional charge and statistics in GaAs. , In the type-II structure shown in Figure b (device 605 or D3), the graphite TG is replaced by lithographically patterned split metallic gates that align vertically with the BG to create the confinement. ,, This structure leaves the interferometer area open to other stimuli, e.g., RF radiation, which will be important for qubit operations. , The GG is used to control n bulk of the interferometer although we will see soon that voltages on the confinement gates, i.e., the TG and BG, have a considerable effect on the carrier density inside the QPC, n qpc .…”

“…The carrier density inside and outside the interferometer n bulk is tuned by a combination of the TG and GG. A strong advantage of the type-I design is the screening provided by the TG and GG, which improves the BLG quality 33,37 and reduces the charging energy of the interferometer, which was critically important in the observation of fractional charge and statistics in GaAs. 8,9 In the type-II structure shown in Figure 1b (device 605 or D3), the graphite TG is replaced by lithographically patterned split metallic gates that align vertically with the BG to create the confinement.…”

“…High-quality monolayer and bilayer graphene-based quantum confinement devices use thin hexagonal-boron nitride (h-BN) sheets as gate dielectrics. − The resulting confinement potential is typically sharper than that in GaAs and the nearby gates offer effective screening. Aharonov–Bohm (AB) oscillations at integer quantum Hall states have been observed recently in monolayer graphene − and bilayer graphene (BLG), respectively.…”

“…Figure a and b show respectively the schematic 3D stacking view of two interferometer designs we explored. They are different from those used in refs , , and . Both include three layers of gates with h-BN as gate dielectrics and additionally a silicon back-gate to dope the contact areas separately, which is not shown.…”