We investigate phase-coherent transport and show Aharonov-Bohm (AB) oscillations in quasiballistic graphene rings with hard confinement. Aharonov-Bohm oscillations are observed in a graphene quantum ring with a topgate covering one arm of the ring. As graphene is a gapless semiconductor, this. Graphene rings in magnetic fields: Aharonov–Bohm effect and valley splitting. J Wurm1,2, M Wimmer1, H U Baranger2 and K Richter1. Published 3 February.

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It supports the sharing of ideas and thoughts within the scientific community, fosters physics teaching and would also like to open a window to physics for all those with a healthy curiosity. Figure 1 a Scanning force microscopy image of device 1 with a schematic of the measurement configuration.

Values are normalized with respect to the conductance at zero B field and an offset is added for clarity. Arrows indicate the direction of the edge channels. The geometrical aspect ratio is roughly one-third of this aspect ratio estimated from the sample resistance at the charge neutrality point.

Standard low-frequency lock-in techniques are used to measure the resistance by applying a constant current. One possible interpretation is that the sample has rough unordered edges leading to a region along the bonm that does not contribute to the electrical transport.

Bachtold A grapheme al Nature Crossref. The relevance of thermal averaging of phase-coherent effects can be judged from the thermal lengthwhich is significantly smaller than L.

On the other hand, the electric field may change the electron density and thereby the Fermi wavelength of the carriers. We therefore graphsne that the smaller ring dimensions in combination with the four-terminal arrangement may be responsible for the larger value of the visibility observed in our experiment.

B 40 Crossref. Magdalena Huefner et al New J. B 79 Crossref.

The Aharonov–Bohm effect in a side-gated graphene ring

We observe that the trajectory of the electron starting in the left lead performs a skipping orbit which after four reflections at the boundary enters the right lead.

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Moreover we show signatures of magnetic grahpene effects at small magnetic fields confirming ballistic transport. While the earlier research interests were focused on the most basic nanostructures, e.

The measured resistance R meas consists of the following parts: Minima and maxima of bphm conductance are approximately horizontal and vertical on this plot. Clear periodic oscillations can be seen on top of this background. We observe that with increasing edge roughness the features of quantization and magnetic focusing weaken until they resemble a shoulder-like structure that was observed in the experiments.

We investigate the magnetoresistance of a side-gated ring structure etched out of single-layer graphene. The conductance for the disk is shown for different strength of edge roughness with the result that the position of the conductance minima are rather robust to edge roughness. B 77 Crossref.

In this work, we have studied the Aharonov—Bohm effect in graphene in a two-terminal ring, but using a four-contact geometry. The only relevant effect of the magnetic field on the charge carrier dynamics is therefore caused by the field-induced Aharonov—Bohm phase.

In athe raw data are shown, while for bthe background has been removed. Hohm up for new issue notifications.

The observations are in good agreement with an interpretation in terms of diffusive metallic transport in a ring geometry. Red dashed lines shows G 2 W used for background subtraction.

Condensed Matter > Mesoscale and Nanoscale Physics

The Institute of Graphehe IOP is a leading scientific society promoting physics and bringing physicists together for the benefit of all. Note that in order for interference to happen at all, part of the wave function has to leak to the reflecting edge channel as otherwise unitarity ensures perfect transmission. 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.


We have observed Aharonov—Bohm oscillations in four-terminal measurements on a side-gated graphene ring structure. The B -field axis is divided into three regimes: Therefore measurements presented here were taken over only small ranges of back gate voltage after having allowed the sample to stabilize in this range. For clarity the trace is duplicated with an offset see red arrow.

The Aharonov–Bohm effect in a side-gated graphene ring – IOPscience

A magnetic field is applied perpendicular to the sample plane. The DPG sees itself as the forum and mouthpiece for physics and is a non-profit organisation that does not pursue financial interests. The density change is related via a parallel plate capacitor model to a change in back gate voltage, i. Received 24 November Published 30 April Ferrari A C et al Phys.

The data are analyzed by a simple dirty metal model justified by grapheene comparison of the different length scales characterizing the system.

We discuss the latter effect in more detail below, since the relative change in the Fermi wavelength is expected to be more pronounced in graphene compared to conventional metals. By continuing to use this site you agree to our use of cookies. We perform tight-binding calculations which allow us to reproduce all significant features of our experimental findings and enable a deeper understanding of the underlying physics.

Weyl fermions are observed in a solid. Zoom In Zoom Out Reset image size. In general, the observed Aharonov—Bohm oscillations become more pronounced for smaller current levels, as expected.

Figure 2 a Solid black line: In diffusive ring-shaped systems, conductance fluctuations can coexist with Aharonov—Bohm oscillations.

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