Aharonov-Bohm oscillations and magnetic focusing in ballistic graphene rings

Abstract

We present low-temperature magnetotransport measurements on graphene rings encapsulated in hexagonal boron nitride. We investigate phase-coherent transport and show Aharonov-Bohm (AB) oscillations in quasi-ballistic graphene rings with hard confinement. In particular, we report on the observation of $h/e$, $h/2e$ and $h/3e$ conductance oscillations. Moreover we show signatures of magnetic focusing effects at small magnetic fields confirming ballistic transport. We perform tight binding calculations which allow to reproduce all significant features of our experimental findings and enable a deeper understanding of the underlying physics. Finally, we report on the observation of the AB conductance oscillations in the quantum Hall regime at reasonable high magnetic fields, where we find regions with enhanced AB oscillation visibility with values up to $0.7$%. These oscillations are well explained by taking disorder into account allowing for a coexistence of hard and soft-wall confinement.

28 pages, 8 figures

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• Boron nitride substrates for high-quality graphene electronics
• Micrometer-scale ballistic transport in encapsulated graphene at room temperature
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• Energy gaps in etched graphene nanoribbons
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• Aharonov-Bohm oscillations in the presence of strong spin-orbit interactions
• Interplay of the Aharonov-Bohm effect and Klein tunneling in graphene
• Fabry-Pérot resonances in a graphene/hBN Moiré superlattice
• Electron optics with dirac fermions: electron transport in monolayer and bilayer graphene through magnetic barrier and their superlattices

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• Four-band effective square lattice model for Bernal-stacked bilayer graphene
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• Electrostatic gate-controlled quantum interference in a high-mobility two-dimensional electron gas at the (La${}_{0.3}$Sr${}_{0.7}$)(Al${}_{0.65}$Ta${}_{0.35}$)O${}_3$/SrTiO${}_3$ interface