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.

Electron-hole hybridization in bilayer graphene

“…Behavior of ballistic electrons in a uniform material resembles that of photons to a high degree [1][2][3][4][5][6][7]35]. For example, electrons follow straight trajectories when considered as particles [16][17][18], while interference effects, such as the Aharonov-Bohm [19][20][21] and Fabry-Perot effects [22], are caused by their wave nature. Due to the conservation of the transverse momentum and the Fermi energy, electron propagation at the boundary of two regions with different carrier densities is subject to reflection and refraction in a way similar to optical rays crossing the boundary of two materials with different refractive indices [23].…”

Electron spin inversion in fluorinated graphene nanoribbons

“…The spin flips occur only for B < 0, i.e. for the magnetic field oriented in the +z direction which injects [45,51] the incident electron wave function from the ribbon to the quantum ring. The injection occurs only provided that a localized resonance is supported by the ring for the applied value of the magnetic field [45].…”

Observation of Landau Level-Dependent Aharonov-Bohm-Like Oscillations in a Topological Insulator

“…Aharonov-Bohm (AB) interference originates from the carrier wavefunction interference in a loop which might be patterned ring [ 1 , 2 ], material geometric structure [ 3 – 6 , 8 – 11 ], or carrier transport trajectory [ 12 ]. The magnetic field, B , through the loop will induce carrier wavefunction phase shift that leads to periodic wavefunction interference oscillations.…”